摘要:

1995 European Winter Conference on Plasma Spectrochemistry 8-13 January 1995 CAMBRIDGE UK Short Courses A series of short courses of one half day duration will take place on Sunday 8th January. Notes and tuition material will be distributed with each course. Courses 1 and 2 Short Courses on ICP-MS Professor R.S. Houk Ames Laboratory Iowa State University USA Course 1 (AM) Instrumentation and Theory The course will cover fundamental aspects of ICP-MS including:- a) Molecular beam sampling b) Quadrupole and high resolution c) Vacuum technology d) Ion sources e) Detection systems and data hand1 ing f) Sample introduction technologies analys ers Course 2 (PM) Advanced Topics The course will cover more advanced topics on ICP-MS particularly relevant to problem solving. Each topic will be illustrated with relevant applications examples.a) Interferences (spectroscopic and non-spectroscopic and methods of alleviation b) Isotopic analysis c) Chromatographic methods d) Overview of commercial instrumentation Course 3 (PM) Sample Preparation for ICPs Dr S.J. Haswell Hull University UK The course will focus on important aspects of sampling and sample preparation with particular emphasis on ICP measurements. a) Batch methods f o r wet oxidation b) Recent trends in microwave preparation for ICP-MS atomic spectrometry general analytical techniques c) On-line sample preparation d) Extraction methods e) On-line chemical processing f) Miniaturization Course 4 (PM) Speciation Professor O.X. Donard University of Bordeaux France The course will focus on practical aspects of speciation analysis with particular emphasis on ICP and other plasma sampling systems.Sample collection and handling preservation and preparation prior to injection into hyphenated systems using atomic spectrometry and ICP-AES or ICP-MS as detectors will be illustrated with applications from current topical fields . a) Sampling and sample pretreatment b) Separative techniques Differential chemistry Gas liquid ion and SCF c ) Interfacing chromatography techniques to ICPs and other plasma sources and detectors chromatographies Course 5 (AM) Quality Systems in the Laboratory Professor L. Ebdon Dr E.H. Evans University of Plymouth UK The course will discuss how high quality analytical data can be produced in the laboratory that are accurate reliable and adequate f o r the intended purpose.a) Quality assurance principles b) Sampling and sample preparation c) Personnel aspects d) Statistics for quality control e Use of reference materials and f) Equipment and records maintenance g) Audits and accreditation. traceability Course 6 (AM) Sample Presentation for ICPS Dr C McLeod Sheffield Hallam University UK The course is intended as a problem solving workshop and will attempt to rationalise the choice of sampling system for ICP spectrometries by use of practical examples. a) Nebulisation techniques Traditional and high efficiency The role of desolvation Hydride Other vapour techniques e . g . b) Vapour generation Hg oso c) Microsampling systems d) Flow injection e) Laser ablation1995 European Winter Conference on Plasma Spectrochemistry 8-13 January 1995 CAMBRIDGE UK Short Courses A series of short courses of one half day duration will take place on Sunday 8th January. Notes and tuition material will be distributed with each course.Courses 1 and 2 Short Courses on ICP-MS Professor R.S. Houk Ames Laboratory Iowa State University USA Course 1 (AM) Instrumentation and Theory The course will cover fundamental aspects of ICP-MS including:- a) Molecular beam sampling b) Quadrupole and high resolution c) Vacuum technology d) Ion sources e) Detection systems and data hand1 ing f) Sample introduction technologies analys ers Course 2 (PM) Advanced Topics The course will cover more advanced topics on ICP-MS particularly relevant to problem solving. Each topic will be illustrated with relevant applications examples.a) Interferences (spectroscopic and non-spectroscopic and methods of alleviation b) Isotopic analysis c) Chromatographic methods d) Overview of commercial instrumentation Course 3 (PM) Sample Preparation for ICPs Dr S.J. Haswell Hull University UK The course will focus on important aspects of sampling and sample preparation with particular emphasis on ICP measurements. a) Batch methods f o r wet oxidation b) Recent trends in microwave preparation for ICP-MS atomic spectrometry general analytical techniques c) On-line sample preparation d) Extraction methods e) On-line chemical processing f) Miniaturization Course 4 (PM) Speciation Professor O.X. Donard University of Bordeaux France The course will focus on practical aspects of speciation analysis with particular emphasis on ICP and other plasma sampling systems.Sample collection and handling preservation and preparation prior to injection into hyphenated systems using atomic spectrometry and ICP-AES or ICP-MS as detectors will be illustrated with applications from current topical fields . a) Sampling and sample pretreatment b) Separative techniques Differential chemistry Gas liquid ion and SCF c ) Interfacing chromatography techniques to ICPs and other plasma sources and detectors chromatographies Course 5 (AM) Quality Systems in the Laboratory Professor L. Ebdon Dr E.H. Evans University of Plymouth UK The course will discuss how high quality analytical data can be produced in the laboratory that are accurate reliable and adequate f o r the intended purpose. a) Quality assurance principles b) Sampling and sample preparation c) Personnel aspects d) Statistics for quality control e Use of reference materials and f) Equipment and records maintenance g) Audits and accreditation. traceability Course 6 (AM) Sample Presentation for ICPS Dr C McLeod Sheffield Hallam University UK The course is intended as a problem solving workshop and will attempt to rationalise the choice of sampling system for ICP spectrometries by use of practical examples. a) Nebulisation techniques Traditional and high efficiency The role of desolvation Hydride Other vapour techniques e . g . b) Vapour generation Hg oso c) Microsampling systems d) Flow injection e) Laser ablation

ISSN:0267-9477    

DOI:10.1039/JA99409FX001

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY INSTRUCTIONS TO AUTHORS The Journal of Analytical Atomic Specrrometn (JAAS ) is an international journal for the publication of original research papers. communications and letters concerned with the development and analytical application of atomic spectrometric techniques. The journal is published bimonthly and also includes comprehensive reviews on specific topics of interest to practising atomic spec- troscopists and incorporates the literature reviews which were previously pub- lished in Annual Reports on Analytical Atomic Spectroscopy (ARAAS). Additional Special Conference Issues are also published. Manuscripts intended for publication as papers or communications must de- scribe original work related to atomic spectrometric analysis.Papers on all as- pects of the subject will be accepted including fundamental studies novel in- strument developments and practical analytical applications. As well as atomic absorption atomic emission and atomic fluorescence spectrometry papers will be welcomed on atomic mass spectrometry X-ray fluorescence/emission spec- trometry and secondary emission spectrometry. Papers describing the measure- ment of molecular species where these relate to the characterization of sources normally used for the production of atoms. or concerning for example indirect methods of anlayses will also be acceptable for publication. Papers describing the development and applications of hybrid techniques involving atomic spec- trometry (e.g. GC coupled AAS and HPLC-ICP) will be particularly welcome.Manuscripts on other subjects of direct interest to atomic spectroscopists in- cluding sample preparation and dissolution and analyte preconcentration proce- dures as well as the statistical interpretation and use of atomic spectrometric data will also be acceptable for publication. Administration and Publication Procedure. Receipt of a contribution for consideration w i l l be acknowledged immediately by the Editorial Office. The acknowledgement will indicate the paper reference number assigned to the con- tribution. Authors are particularly asked to quote this number on a l l subsequent correspondence. All papers (including conference presentations submitted for special issues) are sent simultaneously to at least two referees whose names are not disclosed to the authors.On the basis of the referees' reports. the Editor decides whether the paper i s suitable for publication either unchanged or after appropriate revi- sion. This decision and relevant comments of the referees are communicated to the author. Differences of opinion are mediated by the Editor. possibly after consultation with further referees or. in the last resort. by the Editorial Board When rejection of a paper i s recommended the Editor informs the author and returns the top copy of the manuscript. Authors have the right to appeal to the Editorial Board if they regard a decision to reject as unfair. Authors will receive formal notification when papers are accepted for publi- cation. Proofs. The address to which proofs are to be sent should accompany the paper.Proofs should be carefully checked and returned immediately (by first class mail air mail or fax). Particular attention should be paid to numerical data both in the tables and text. Although short articles are acceptable. the Society strongly discourages frag- Reprints. Fifty reprints of each paper are supplied free on request. Additional reprints can be purchased i f ordered at the time of publication. Details are sent to authors with the proofs. mentation of a substantial body of work into a number of short publications. Unnecessary fragmentation will be 3 valid reason for rejection of manuscripts. There i s no page charge for papers published in JAAS. Notes on the Writing of Papers for JAAS The following types of papers will be considered.Original research paper.$. Cornmunic-ations which must be on an urgent matter and be of obvious Manuscripts should be in accordance with the style and usage shown in re- cent copies of JAAS. Conciseness of expression i s expected clarity i s increased by adopting a logical order of presentation. with suitable paragraph or section headings. Spellings should be in accordance with the Oxford English Dictionary. scientific importance. Rapidity of publication i s enhanced i f diagrams are orit and are usual,y published within 2-3 months of receipt They are intended to be valuable to workers faced with similar problems. A fuller paper may be but tables and formulae may be included Communic~ions receive To facilitate abstracting and indexing by Chemical Abstracts Service and other abstracting organizations i t would be helpful i f at least one forename should be for brief deg-riptions of work that has progressed to a stage at which i t is likely be included with each author's name' The author indicated' .. offered subsequently. if justified by later work. Although publication i s at the discretion of the Editor communications will be examined by at least one referee. Descriptions of methods should be supported by experimental results show- The recommended order of presentation i s as indicated below ing accuracy precision and selectivity. Reviews. which must be a critical evaluation of the existing state of knowl- edge on a particular facet of analytical chemistry. However original work may be included. Simple literature surveys will not be accepted for publication.I t i s desirable that potential review writers should contact the Editor before embark- ing on their work. Copyright. The whole of the literary matter (including tables. figures dia- grams and photographs) in JAAS is Royal Society of Chemistry copyright and may not be reproduced without permission from the Society or such other owner of the copyright as may be indicated. Papers that are accepted must not be published elsewhere except by permission. Submission of a manu- script will be regarded as an undertaking that the same material i s not being considered for publication by another journal in any language. European Associate Editor. Papers from Europe can be submitted to Judith Egan-Shuttler Storchenweg 17 W-7772 Unteruhldingen Germany.CIS Associate Editor. Papers from North America can be submitted to Dr. J . M. Harnly US Department of Agriculture. Beltsville Human Nutrition Research Center. BLDG 161 BARC-EAST. Beltsville. MD 20705. USA. Manuscripts. Papers should be typewritten in double spacing on one side on!v of the paper. Copies of any related relevant unpublished material and raw data should be made available on request. Each table and illustration should be on a separate sheet at the end of the text; three copies of text and illustrations should be sent to the Editor JAAS The Royal Society of Chemistry Thomas Graham House Science Park Milton Road Cambridge CB4 4WF or directly to the US Associate Editor. and a further copy retained by the author. (0) Title.This should be as brief as i s consistent with an adequate indication of the original features of the work. The title should usually include the analyte being determined or identified. the matrix and the analytical method used. ( b ) Summap. A summary of about 250 words giving the salient features and drawing attention to the novel aspects should be provided for a l l pa- pers. I t should be essentially independent of the main text and include relevant quantitative information such as detection limits precihion and accuracy data. (c) Keynwrds. Up to five keywords or key phrases. indicating the topics of importance in the work described should be included after the summary. t d ) Aim ofinvesrigorion. A concise introductory statement of the novel fea- tures of the work and the object of the investigation with any essential historical background.followed if necessary by a brief account of prc liminary expcrimental work with relevant references. ( e ) Description of the experimen/al procedures. Working details must be given concisely. Analytical procedures should be given in the form of instructions; well known operations should not be described in detail. Suppliers of equipment and materials and their locations. should be mentioned. 0 Results and Discussion. Results are best presented in tabular or diagram- matic form (but not both for the same results). followed by an appropri- ate statistical evaluation which should be in accordance with accepted practice. For example. a new procedure for multi-element determinations which produced results for which the concentration of 8 out of 10 of the elements determined in a standard reference material were statisticallyindistinguishable from the certificate values should be described in those terms and not referred to as 'excellent agreement'.This is particularly important in the summary. Any discussion should comment on the scope of the method and its validity followed by a statement of any conclusions drawn from the work. A separate conclusions section is not encouraged but if included it should not simply duplicate state- ments in the discussion. ( 8 ) Acknowledgemenrs. Contributions other than co-authors companies or sponsors may be acknowledged in a separate paragraph at the end of the paper. Titles may be given but not degrees.( h ) References. References should be numbered serially in the text by means of superscript figures. e.8.. F ~ t c and Dclves.1 Burns et a/. or ... in a recent paper...' and collected in numerical order under 'References' at the end of the paper. They should be listed. with all the authors' names and initials. in the following form (double-spaced typing) Yerian T. D.. Christian G. D.. and R&i<ka. J.. Analyst. 1986. 111. 865. Sharp B. L.. Barnett. N. W.. Burridge J. C.. Littlejohn D.. and Tyson. J. F.. J. Anal. At. Spectrom. 1988.3. 133R. Committee for Analytical Methods for Residues of Pesticides and Veterinary Products in Foodstuffs and the Working Party on Pesticide Residues of the Ministry of Agriculture Fisheries and F d Analyst. 1985 110,765. Hara H..Horvai G.. and Pungor E. Analyst 1988. 113. 1817; Anal. Abstr.. 1989.51.6H57. Norwitz. G. and Keliher P. N.. Analyst. 1987 112. 903 (and references cited therein). L'vov. B. V. Polzik. L. K.. Romanova. N. P.. and Yuzeforskii. A. I. J. Anal. At. Spectrom.. in the press. O'Connor. A.. Sigma St. Louis MO. personal communication. 1989. Appelqvist. R. Ph. D. Thesis University of Lund. Sweden. 1987. Bi. C. Evans E. H. and Caruso J. A. paper presented at the 1992 Winter Conference on Plasma Specctrochemistry San Diego. CA USA January 6-1 I 1992. Journal titles should be abbreviated according to the Chemical Abstracts Service Source Index (CASSI). The abbreviation for this journal is J. Anal. At. Spertrom. For books. the edition (if not the first) the publisher and the place and date of publication should be given followed by the page number.Harrison. W. W. and Donohue. D. L. in Treatise on Analytical Chemistry. eds. Kolthoff I. M. and Winefordner J. D. Wiley New York 2nd edn.. Gutscht. C. D.. Calixurenes Royal Society of Chemistry Cambridge. 1989. British Pharmacopoeia 1988 HM Stationery Office London 1988. vol. I p. 140. RGiicka J. and Hansen E. H. Flow Injection Analysis. 2nd edn.. Wiley. New York 1988 pp. 299-304. Moody. G. J.. and Thomas J. D. R. in Ion Selective Electrodes in Analytical Chemistry. ed. Freiser H. Plenum New York 1978 ch. 4. Beauchemin D. and Craig J. M.. in Plasm Source Mass Spectrometry. The Proceedings of the Third Surrey Conference on Plasma Source Mms Spectrometry. University of Surrey. July 16th-19th.1989. eds. Jarvis. K. E.. Gray. A. L.. Jarvis. I.. and Williams. J. G.. The Royal Society of Chemistry Cambridge 1990 pp. 25-42. OIJicial Methods of Analysis of the Association of Oficial Analyricol Chemists. ed. Horwitz W.. Association of Official Analytical Chemists Arlington VA 13th edn.. 180. sect. 20.104. 1989 PI. I VOI. I I. ch. 3. pp. 189-235. Authors must. in their own interest check the lists of references against the original papers; second-hand references are a frequent source of error. References 10 conference abstracts which have not been published in the open lit- erature are not acceptable. The number of references must be kept to a minimum. Nnmencluture. Current internationally recognized (IUPAC) chemical nomen- clature should be used. Common trivial names may be used but should first be defined in terms of IUPAC nomenclature.A listing of all relevant IUPAC nomenclature publications appears in the February issue. Symbols und units. The SI system of units as recommended by IUPAC. should be followed. Their basis is the 'Systeme lnternationale d'Unitks' (SI). A detailed treatment is given in the 'Green Book' Quantities. Units and Symbols in Physical Chemistry (Blackwell. Oxford I988 edn.). The following will be the guidelines used ( a ) A metric system will always be used in preference to a non-metric one. ( b ) SI will be the standard usage. ( c ) The units used to record the definitive values of 'critical data' or quanti- ties measured to a high degree of accuracy will be S1. These units are summa- rized in the Appendix.The effect on current style of papers for JAAS includes the following ( a ) dimensions should preferably be given in metres (m) or in millimetres ( b ) temperatures should be expressed in K or "C (not OF); ( c ) wavelengths should be expressed in nanometres (nm) not mCI; (6) frequency should be expressed in Hz (or kHz etc.). not in c/s or c.P.s.; rotational frequency can be denoted by use of s-I; in mass spectrometry signal intensity should be expressed in counts s-I and not in Hz; (mm); ( e ) radionuclide activity should be expressed in becquercls (Bq); fl the micron (p) will not be used; 10" will be Ipm. When non-S1 units arc used they must be adequately explained unless their definition is obvious ((-8.. "C and A). The derivation of derived non-SI units should be indicated. Abbreviations.Abbreviational full stops are omitted after the common contractions of metric units (e.g.. ml. g. pg mm) and other units represented by symbols. Abbreviations other than those of recognized units should be avoided in the text except after definition. Upper case letters without points should be used for abbreviations for techniques and associated terms subsequent to defini- tion e.g. HPLC AAS XRF UV NMR SCE. Other common abbreviations and contractions require full points e.g.. q n . m.p.. Dr. except when sub- or super-script. & for example. The abbreviations Me Et PF Bun. Bu' BU Bul. Ph Ac. Alk Ar and Hal can be used; others should be defined. Carboxy groups are written CO,R. not COOR. Substituents should be indicated by R (one) or by R' R'.R' ... (more than one). Percentage concentrations of solutions should be stated in internationally recognized terms. Thus the symbols 'm' instead of 'w' for mass and 'v' for vol- ume are to be used. The following show the manner of expressing these per- centages together with an acceptable alternative given in parentheses % m/m (g per 100 8); 96 d v (g per 100 mi); % v/v. Further implications of the use of the term 'mass' are that 'relative atomic mass' of an element (A,) replaces atomic weight and 'relative molecular mass' of a substance (M,) replaces molecular weight. Concentrations of solutions of the common acids are often conveniently given as dilutions of the concentrated acids such as 'dilute hydrochloric ( I +4)' which signifies 1 volume of the concentrated acid mixed with 4 volumes of water.This avoids the ambiguity of I 4 which might represent either I + 4 or I + 3. Dilutions of other solutions should be expressed in a similar manner. Molarity is generally expressed as a decimal fraction (e.g. 0.375 mol dm-'). Tables and diagrams. Table column headings should be brief. Tables con- sisting of only two columns can often be arranged horizontally. Tables must be supplied with titles and be so set out as to be understandable without reference to the text. Either tables or graphs may be used but not both for the same set of results unless important additional information is given by so doing. The information given by a straight-line calibration graph can usually be conveyed adequately as an equation or statement in the text.Column headings and graph axis labels should be in accord with SI conven- tions. Thus the expression of numerical values of a physical quantitiy should be dimensionless. i.e. the quotient of the symbol for the physical quantity and the symbol for the unit used e.g.. pPa or some mathematical function of a number. e.g. In @/Pa). Further examples are v/cm-I Ucm. mass of substance/g and flow rate/ml min-I. For units which are already dimensionless. i.e. ratios such as 9% or ppm the type of ratio is indicated in parentheses e.g. e (96) or e (ppm). The diagonal line (solidus) will not be used to represent 'per'. In accor- dance with the S1 system units such as grams per millilitre are already ex- pressed in the form g m1-I.It should be noted that the 'combined' unit g ml-' must not have any 'intrusive' numbers. To express concentration in grams per 100 millilitrcs. the word 'per' will still be required Concentration/g per 1 0 ml. It may be preferable for an author to express concentrations in grams per litre (g I - ' ) rather than grams per 100 mi.Most diagrams will be retraced and lettered in order to achieve uniform line thickness and lettering size and style. However all diagrams should be carefully and clearly drawn on good quality paper and should be carefully and clearly lettered. I f possible chromatograms and spectra complicated flow charts circuit digrams. ptc'. should be supplied as artwork for direct reproduction in order 10 avoid time-consuming and expensive redrawing.The clearest copy should be without lettering. Three complete sets of illustrations should be provided two sets of which may be made by any convenient copying process for transmission to the referees. All diagrams should be accompanied by a separately typed set of cap- tions. Wherever possible extensive identifying lettering should be placed in the caption rather than on lines on graphs. erc. Photographs. Photographs can be submitted if they convey essential in- formation that cannot be shown in any other way. They should be submitted as glossy or matt prints made to give the maximum detail. Colour pho- tographs will be accepted only when a black-and-white photograph fails to show some vital feature and can be supplied either as prints or transparen- cies. Appendix I The SI System of Unlts In the SI system there are seven base units- Symbol for Name Symbol Physical quantiry quantity of unit for unit length l metre m mass m kilogram kg time t second S electric current I ampere A thermodynamic temperature T kelvin K amount of substance n mole mol luminous intensity 1 candela cd There are two supplementary dimensionless units for plane angle (radian rad) and solid angle (steradian sr).Some derived SI units that have special names are as follows- Physical frequency force pressure stress energy work heat power electric charge electric potential electric capacitance electric resistance electric conductance magnetic flux magnetic flux density inductance Celcius temperature plane angle solid angle Name of unit hertz newton pascal joule watt coulomb volt farad ohm siemens weber tesla henry degree Celsius radian steradian Symbol for unit Hz N Pa J W C V F R S Wb T H "C K rad I sr I Examples of other derived SI units with no special names or symbols are- Physical quantity S1 unit area volume density velocity angular velocity acceleration pressure kinematic viscosity diffusion coefficient dynamic viscosity electric field strength magnetic field strength luminance square metre cubic metre kilogram per cubic metre metre per second radian per second metre per second squared newton per square metre square metre per second newton second per square metre volt per metre ampere per metre candela per square metre Certain units will be allowed in conjunction with the SI system e.g.- Symbol Physical quantity Name of unit for unit time plane angle volume magnetic flux density (magnetic induction) temperature t energy pressure mass minute degree litre gauss degree Celsius electronvolt bar unified atomic mass unit min I G "C eV bar 0 U Symbol for SI unit m' m' k m-' m s-' rad s-' m s- N m-' m 2 s-l N s m-' V m-' A m-I cd m-' Definition of unit 60s (tdl80) rad lo-' m' = dm' T tl°C = TIK - 273.16 I .602 I x 10-I' J 10' Pa 1.660 54 x lo-'' kgThe other common units of time (e.g..hour and day) will continue to be used in appropriate contexts. Decimal multiples and submultiples have the following names and symbols (for use as prefixes)- 10.' 10" lo-" lo-'! lo-" lo-'" lo-?' lo-?' milli micro nano pic0 femto atto zepto yocto 10' lo" lo' 10' 10" 10'" 10'' 10:' kilo mega gigs tera pet a exa zetta yotta Compound prefixes (e.g.mpm) should not be used; 10." m = I nm. Appendix II Abbreviations Whenever suitable elements may be referred to by their chemical symbols and compounds by their formulae. fined at the first place of mention. The following abbreviations will be used extensively in the Atomic Spectrometry Updates and may be used in original papers provided that they are de- ax. AA AAS AE AES AF A FS AOAC APDC ASV CCP CMP CRM cw d.c. DCP DDDC D M F DNA EDL EDTA EDXRF EIE EPMA ETA ETAAS ETV EXAFS FA AS FAB FAES FAFS FI FPD FT FTMS GC CD GDL GDMS Ge (Li) HCL h.f. HG HPGe HPLC IAEA l0MK ICP ICP-MS IR IUPAC alternating current atomic absorption atomic absorption spectrometry atomic emission atomic emission spectrometry atomic fluorescence atomic fluorescence spectrometry Association of Official Analytical Chemists ammonium pyrrolidinedithiocarbamate (ammonium pyrrolidin- 1 -yl anodic-stripping voltammetry capacitively coupled plasma capacitively coupled microwave plasma certified reference material continuous wave direct current d.c.plasma diammonium diethyldithiocarbamate N. N-dimethylformamide deoxyribonucleic acid electrodeless discharge lamp ethylenediaminetetraacetic acid energy dispersive X-ray fluorescence easily ionizable element electron probe microanalysis electrothermal atomization electrothermal atomic absorption Spectrometry electrothermal vaporization extended X-ray absorption fine structure spectroscopy flame AAS fast atom bombardment flame AES flame AFS flow injection Flame photometric detector Fourier transform Fourier transform mass spectrometry gas chromatography glow discharge glow discharge lamp glow discharge mass spectrometry lithium-drifted germanium hollow cathode lamp high frequency hydride generation high-purity germanium high-performance liquid chromatography International Atomic Energy Agency isobutyl methyl ketone (4-methylpentan-2-one) inductively coupled plasma inductively coupled plasma mass spectrometry infrared International Union of Pure and Applied Chemistry dit hioformate) LA LC LEAFS LEI LMMS LOD LTE MECA MIP MS NAA NaDDC NlES NlST NTA OES PlGE PIXE PMT PPm F'TFE Qc r.f.REE( s) RIMS RM RSD SIB SEC SEM S I T Si( Li) SIMAAC SlMS SIN SR SRM SSMS STPF TCA TlMS TLC TOP0 TXRF u.h.f. uv VDU vuv WDXRF XRF PPb laser ablation liquid chromatography laser-exci ted atomic fluorescence spectrometry laser-enhanced ionization laser microprobe mass spectrometry limit of detection local thermal equilibrium molecular emission cavity analysis microwave-i nduced plasma mass spectrometry neutron activation analysis sodium diethylidithiocarbamate National Institute for Environmental Studies National Institute of Standards and Technology nitrilotriacetic acid optical emission spectrometry particle-induced gamma-ray emission particle-induced X-ray emission photomultiplier tube parts per billion parts per million polytetrafluoroethylene quality control radiofrequency rare earth elernent(s) resonance ionization mass spectrometry reference material relative standard deviation signal to background ratio size-exclusion chromatography scanning electron microscopy supercritical fluid chromatography lithium-drifted silicon simultaneous multi-element analysis with a continuum source secondary ion mass spectrometry signal to noise ratio synchrotron radiation Standard Reference Material spark source mass spectrometry stabilized temperature platform furnace t ric hloroacet ic acid thermal ionization mass spectrometry thin-layer chromatography trioctylphosphine oxide total reflection X-ray fluorescence ultra-high-frequency ultraviolet visual display unit vacuu m ultraviolet wavelength dispersive X-ray fluorescence X-ray fluorescence The Royal Society of Chemistry.Thomas Graham House. St.ience fork. Milron Roud Ci!mbridgP. UK. CB4 4WF. Telephone +44 (0)223 420066; Fax +44 ( 0 ) Z Z - j 420247 E-muil RSC09 @lJK.AC.RL.GB (JANET)

ISSN:0267-9477    

DOI:10.1039/JA994090X003

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 IUPAC Publications on Nomenclature and Symbolism 1 .O Compilations 1.1 Nomenclature of Organic Chemistry a 550-page hardcover volume published in 1979 available from Pergamon Oxford. Section A Hydrocarbons Section €3 Fundamental heterocyclic systems Section C Characteristic groups containing carbon hy- drogen oxygen nitrogen halogen sulfur selenium and tellurium Section D Organic compounds containing elements not exclusively those referred to in the title of Section C Section E Stereochemistry Section F General principles for the naming of natural products and related compounds Section H Isotopically modified compounds 1.2 A Guide to IUPAC Nomenclature of Organic Compounds a 182-page hardcover volume published in 1993 available from Blackwell Scientific Publications Oxford to be used in conjunction with item 1.1.1.3 Nomenclature of Inorganic Chemistry a 278-page hardcover volume published in 1990 available from Blackwell Scientific Publications Oxford. Chapter 1 General aims functions and methods Chapter 2 Grammar Chapter 3 Elements atoms and groups Chapter 4 Formulae Chapter 5 Names based on stoichiometry Chapter 6 Neutral molecular compounds Chapter 7 Names for ions substituent groups and radicals and salts Chapter 8 Oxoacids and derived anions Chapter 9 Co-ordination compounds Chapter 10 Boron hydrides and related compounds 1.4 Biochemical Nomenclature and Related Documents a 348-page softcover manual published in 1992 by Portland Press Ltd. for IUBMB and available from the publisher (59 Portland Place London W 1 N 3AJ UK).The contents are as follows Nomenclature of organic chemistry. Section E Stereo- chemistry ( 1974) Nomenclature of organic chemistry. Section F Natural products and related compounds (1976) Isotopically modified compounds Recommendations for the presentation of thermodynamic and related data in biology (1985) Citation of bibliographic references in biochemical journals ( 197 1 ) Nomenclature and symbolism for amino acids and peptides ( 1983) Abbreviated nomenclature of synthetic polypeptides or polymerized amino acids ( 197 1 ) Abbreviations and symbols for the description of the conformation of polypeptide chains (1969) Nomenclature of peptide hormones (1 974) Nomenclature of glycoproteins glycopeptides and peptidoglycans ( 1985) Nomenclature of initiation elongation and termination factors for translation in eukaryotes (1 988) Nomenclature of multiple forms of enzymes (1976) Symbolism and terminology in enzyme kinetics (1981) Nomenclature for multienzymes ( 1989) Abbreviations and symbols for nucleic acids poly- nucleotides and their constituents (1970) Abbreviations and symbols for the description of the conformations of polynucleotide chains ( 1 982) Nomenclature for incompletely specified bases in nucleic acid sequences (1 984) Carbohydrate nomenclature. Part I ( 1969) Nomenclature of cyclitols ( 1973) Numbering of atoms in myo-inositol (1988) Conformational nomenclature for five- and six-membered ring forms of monosaccharides and their derivatives (1980) Nomenclature of unsaturated monosaccharides ( 1980) Nomenclature of branched-chain monosaccharides (1 980) Abbreviated terminology of oligosaccharide chains (1 980) Polysaccharide nomenclature ( 1980) Symbols for specifying the conformation of polysaccharide chains (1 98 1 ) Nomenclature of lipids (1 976) Nomenclature of steroids (1 989) Nomenclature of quinones with isoprenoid side chains (1 973) Nomenclature of carotenoids (1 970) and amendments Nomenclature of tocopherols and related compounds (1981) Nomenclature of vitamin D ( 198 1) Nomenclature of retinoids (1 98 1) Prenol nomenclature (1986) Nomenclature of phosphorus-containing compounds of biochemical importance ( 1976) Nomenclature and symbols for folic acids and related compounds (1986) Nomenclature for vitamins B-6 and related compounds (1 973) Nomenclature of corrinoids (1973) Nomenclature of tetrapyrroles (1 986) (1 974) 1.5 Compendium of Analytical Nomenclature a 280-page hardcover volume published in 1987 available from Blackwell Scientific Publications Oxford.The contents are as follows Presentation of the Results of Chemical Analysis Solution Thermodynamics (activity coefficients equilibria PHI Recommendations for Terminology to be used with Precision Balances Recommendations for Nomenclature of Thermal Analysis Recommendations for Nomenclature of Titrimetric Analysis Electrochemical Analysis Analytical Separation Processes (precipitation liquid- liquid distribution zone melting and fractional crystallis- ation chromatography ion exchange) Spectrochemical Analysis (radiation sources general atomic emission spectroscopy flame spectroscopy X-ray emission spectroscopy molecular methods) Recommendations for Nomenclature of Mass Spec- trometry Recommendations for Nomenclature of Radiochemical Methods Surface Analysis (including photoelectron spectroscopy)INSTRUCTIONS FOR AUTHORS (1 994) 1.6 Compendium of Macromolecular Nomenclature a 172-page hardcover volume published in 199 1 available from Blackwell Scientific Publications Oxford.The contents are as follows Basic Definitions of Terms Relating to Polymers Stereochemical Definitions and Notations Relating to Polymers Definitions of Terms Relating to Individual Macromolecules their Assemblies and Dilute Polymer Solutions Definitions of Terms Relating to Crystalline Polymers Nomenclature of Regular Single-strand Organic Polymers Nomenclature for Regular Single-strand and Quasi-single- strand Inorganic and Coordination Polymers Source-based Nomenclature for Copolymers A Classification of Linear Single-strand Polymers Use of Abbreviations for Names of Polymeric Substances 1.7 Compendium of Chemical Terminology IUPAC Recommendations a 456-page volume published in 1987 available in hardcover and softcover from Blackwell Scientific Publications Oxford.1.8 Quantities Units and Symbols in Physical Chemistry a 166-page softcover volume published in 1993 by Blackwell Scientific Publications Oxford. 2.0 Documents not included in the compil- ations 2.1 Boron Compounds Nomenclature of inorganic boron compounds (Pure Appl. Chem.1972,30,681). Delta Convention Nomenclature for cyclic organic compounds with contiguous formal double bonds (Pure Appl Chem. 1988,60,1395). Recommendations for the names of elements of atomic number greater than 100 (Pure Appl. Chem. 1979,51,381). Enzyme Nomenclature (1992) published by Academic Press in hardcover and softcover editions. Revision of the extended Hantzsch-Widman system of nomenclature for heteromonocycles (Pure Appl. Chem. 1983 55,409). Names for hydrogen atoms ions and groups and for reactions involving them (Pure Appl. Chem. 1988,60 11 15). Nomenclature of inorganic chemistry. Part 11. 1. Isotopically modified compounds (Pure Appl. Chem. 198 1,53,1887). Treatment of variable valence in organic nomenclature (Pure Appl. Chem. 1984,56 769). Nomenclature of hydrides of nitrogen and derived cations anions and ligands (Pure Appl.Chem. 1982,54,2545). Extension of Rules A-1 1 and A-2.5 concerning numerical terms used in organic chemical nomenclature (Pure Appl. Chern. 1986,58 1693). Nomenclature of polyanions (Pure Appl. Chem. 1987,59,1529). Nomenclature of regular double-strand (ladder and spiro) organic polymers (Pure Appl. Chem. 1993,65 1561). Nomenclature of Elements and Compounds Elements Enzymes Heterocyclic Compounds Hydrogen Isotopically Modified Compounds Lambda Convention Nitrogen Hydrides Numerical Terms Polyan ions Polymers Radicals and Ions Revised nomenclature for radicals ions radical ions and related species (Pure Appl. Chem. 1993,65 1357). Chemical nomenclature and formulation of compositions of synthetic and natural zeolites (Pure Appl.Chem. 1979 51 1091). Zeolites 2.2 Terminology Symbols and Units and Presentation of Results Glossary of terms used in physical organic chemistry (Pure Appl. Chem. 1983,55 1281). Glossary of atmospheric chemistry terms (Pure Appl. Chem. 1990,62 2167). English-derived abbreviations for experimental techniques in surface science and chemical spectroscopy (Pure Appl. Chem. 1991,63 887). Analytical Recommendations for publication of papers on a new analytical method based on ion exchange or ion-exchange chromatography (Pure Appl. Chern. 1980,52,2555). Recommendations for presentation of data on compleximetric indicators 1. General (Pure Appl. Chem. 1979,51 1357). Recommendations for publishing manuscripts on ion-selective electrodes (Pure Appl.Chem. 1981 53 1907). Recommendations on use of the term amplification reactions (Pure Appl. Chem. 1982,54,2553). Recommendations for the usage of selective selectivity and related terms in analytical chemistry (Pure Appl. Chem. 1983 55 553). Nomenclature for automated and mechanised analysis (Pure Appl. Chem. 1989,61 1657). Nomenclature for sampling in analytical chemistry (Pure Appl. Chem. 1990,62 1193). Nomenclature for chromatography (Pure Appl. Chem. 1993 65,8 19). Glossary for chemists of terms used in biotechnology (Pure Appl. Chem. 1992,64 143). Selection of terms symbols and units related to microbial processes (Pure Appl. Chem. 1992,64 1047). Physicochemical quantities and units in clinical chemistry with special emphasis on activities and activity coefficients (Pure Appl.Chem. 1984,56 567). Quantities and units in clinical chemistry (Pure Appl. Chem. 1979,51 2451). Quantities and units in clinical chemistry nebulizer and flame properties in flame emission and absorption spectrometry (Pure Appl. Chem. 1986,58 1737). List of quantities in clinical chemistry (Pure Appl. Chem. 1979 51,2481). Proposals for the description and measurement of carry-over effects in clinical chemistry (Pure Appl. Chem. 1991,63 301). Quantities and units for metabolic processes as a function of time (Pure Appl. Chem. 1992,64 1569). Glossary for chemists of terms used in toxicology (Pure Appl. Chem. 1993,65,2003). Definitions terminology and symbols in colloid and surface chemistry. I (Pure Appl. Chem. 1972 31 577). 11 Hetero- geneous catalysis (Pure Appl.Chem. 1976 46 71). Part 1.14 Light scattering (provisional) (Pure Appl. Chem. 1983 55 93 1). Reporting experimental pressure-area data with film balances (Pure Appl. Chem. 1985,57,621). General Biotechnology Clinical Colloids and Surface ChemistryINSTRUCTIONS FOR AUTHORS (1994) Reporting physisorption data for gaslsolid systems with special reference to the determination of surface area and porosity (Pure Appl. Chem. 1985,57,603). Reporting data on adsorption from solution at the solid/ solution interface (Pure Appl. Chem. 1986,58,967). Manual on catalyst characterization (Pure Appl. Chem. 1991 63 1227). Nomenclature for transfer phenomena in electrolytic systems (Pure Appl. Chem. 1981,53 1827). Electrode reaction orders transfer coefficients and rate cons tan ts-amplifica tion of definitions and recommenda tions for publication of parameters (Pure Appl.Chem. 1980,52,233). Classification and nomenclature of electroanalytical techniques (Pure Appl. Chem. 1976,45,81). Recommendations for sign conventions and plotting of electrochemical data (Pure Appl. Chem. 1976,45 13 1). Electrochemical nomenclature (Pure Appl. Chem. 1974,37,499). Recommendations on reporting electrode potentials in non- aqueous solvents (Pure Appl. Chem. 1984,56,461). Definition of pH scales standard reference values measurement of pH and related terminology (Pure Appl. Chem. 1985 57 53 I). Interphases in systems of conducting phases (Pure Appl. Chem. 1986,58,437). The absolute electrode potential an explanatory note (Pure Appl.Chem. 1986,58,955). Electrochemical corrosion nomenclature (Pure Appl. Chem. 1989,61 19). Terminology in semiconductor electrochemistry and photo- electrochemical energy conversion (Pure Appl. Chem. 199 1,63 569). Nomenclature symbols definitions and measurements for electrified interfaces in aqueous dispersions of solids (Pure Appl. Chem. 1991,63 895). Nomenclature symbols and definitions in electrochemical engineering (Pure Appl. Chem. 1993,65 1009). Symbolism and terminology in chemical kinetics (provisional) (Pure Appl. Chem. 1981,53 753). Recommended standards for reporting photochemical data (Pure Appl. Chem. 1984,56,939). Glossary of terms used in photochemistry (Pure Appl. Chem. 1988,60 1055). Expression of results in quantum chemistry (Pure Appl.Chem. 1978,50 75). Reactions Nomenclature for organic chemical transformations (Pure Appl. Chem. 1989,61 725). System for symbolic representation of reaction mechanisms (Pure Appl. Chem. 1989,61,23). Elect rochem is t ry Kinetics Photochemistry Quan t um Chemistry Detailed linear representation of reaction mechanisms (Pure Appl. Chem. 1989,61 57). Rheo logical Properties Selected definitions terminology and symbols for rheological properties (Pure Appl. Chem. 1979 51 1215). Recommendations for publication of papers on methods of molecular absorption spectrophotometry in solution (Pure Appl. Chem. 1978,50,237). Recommendations for the presentation of infrared absorption spectra in data collections. A Condensed phases (Pure Appl. Chem. 1978,50,231).Definition and symbolism of molecular force constants (Pure Appl. Chem. 1978,50 1709). Nomenclature and conventions for reporting Mossbauer spectroscopic data (Pure Appl. Chem. 1976,45,211). Recommendations for the presentation of NMR data for publication in chemical journals. A Proton spectra (Pure Appl. Chem. 1972,29,625). B Spectra from nuclei other than protons (Pure Appl. Chem. 1976,45,217). Presentation of Raman spectra in data collections (Pure Appl. Chem. 1981,53 1879). Names symbols definitions and units of quantities in optical spectroscopy (Pure Appl. Chem. 1985,57 105). A descriptive classification of the electron spectroscopies (Pure Appl. Chem. I987,59 1343). Presentation of molecular parameter values for IR and Raman intensity (Pure Appl. Chem.1988,60 1385). Recommendations for EPR/ESR nomenclature and conven- tions for presenting experimental data in publications (Pure Appl. Chem. 1989,61,2195). Nomenclature symbols units and their usage in spectro- chemical analysis. VII. Molecular absorption spectroscopy UV and visible (Pure Appl. Chem. 1988 60 1449); VIII. Nomenclature system for X-ray spectroscopy (Pure Appl. Chem. 1991,63,735); X . Preparation of materials for analytical atomic spectroscopy (Pure Appl. Chem. 1988 60 1461); XII. Terms related to electrothermal atomization (Pure Appl. Chem. 1992 64 253); XIII. Terms related to chemical vapour generation (Pure Appl. Chem. 1992,64,261). Recommendations for nomenclature and symbolism for mass spectroscopy (Pure Appl. Chem. 1991,63 1541). A guide to procedures for the publication of thermodynamic data (Pure Appl. Chem. 1972,39 395). Assignment and presentation of uncertainties of the numerical results of thermodynamic measurements (Pure Appl. Chem. 1981 53 1805). Notation for states and processes; significance of the word ‘standard’ in chemical thermodynamics and remarks on commonly tabulated forms of thermodynamic functions (Pure Appl. Chem. 1982,54 1239). Spectroscopy Thermodynamics

ISSN:0267-9477    

DOI:10.1039/JA994090X007

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

JOURNALS OF THE ROYAL SOCIETY OF CHEMISTRY Refereeing Procedure and Policy (I 994) 1.0 Contributions t o Dalton Perkin and Faraday Transactions J. Mater. Chem. The Analyst J. Anal. At. Spectrom. and J. Chem. Research 1.1 Introduction This document summarises the procedure used for assessing papers submitted to the four Transactions J. Mater. Chem. The Analyst J. Anal. At. Spectrom. and J. Chem. Research and provides guidelines for referees engaged in this assessment. 1.2 Subject Matter Papers are submitted to the various journals according to subject matter:If it is felt that a paper would be published more appropriately in an RSC journal other than the one suggested by the author the referee should inform the Editor. The topics covered by the various journals are as follows. Dalton Transactions (Inorganic Chemistry).All aspects of the chemistry of inorganic and organometallic compounds including bioinorganic chemistry and solid-state inorganic chemistry; the applications of physicochemical techniques to the study of their structures properties and reactions including kinetics and mechanism; new or improved experimental techniques and syntheses. Faraday Transactions (Physical Chemistry and Chemical Physics). Gas-phase kinetics and dynamics; molecular beam kinetics and spectroscopy photochemistry and photophysics; energy transfer and relaxation processes laser-induced chemistry; spectroscopies of molecules molecular and gas- phase complexes quantum chemistry and molecular structure statistical mechanics of gaseous molecules and complexes; spectroscopies statistical mechanics and quantum theory of the condensed phase computational chemistry and molecular dynamics; colloid and interface science surface science physisorption and chromatographic science chemisorption and heterogeneous catalysis zeolites and non-exchange phenomena; electrode processes liquids and solutions; solid-state chemistry (microstructures and dynamics); reactions in condensed phases; physical chemistry of macromolecules and polymers; materials science; thermodynamics; biophysical chemistry and radiation chemistry.Perkin Transactions I (Organic Chemistry). All aspects of organic and bio-organic chemistry. These include synthetic organic chemistry of all types organometallic chemistry chemistry and biosynthesis of natural products the relationship between molecular structure and biological activity the chemistry of polymers and biological macromolecules and medicinal and agricultural chemistry where there is originality in the science.Perkin Transactions 2 (Physical Organic Chemistry). Physicochemical aspects of organic organometallic and bio- organic chemistry including kinetic mechanistic structural spectroscopic and theoretical studies. Such topics include structure-activity relationships and physical aspects of biological processes and of the study of polymers and biological macromolecules. Journal of Materials Chemistry. The chemistry of materials particularly those associated with advanced technology; modelling of materials; synthesis and structural characteris- ation; physicochemical aspects of fabrication; chemical structural electrical magnetic and optical properties; applic- ations.The Analyst (Analytical Science). Theory and practice of all aspects of analytical chemistry fundamental and applied inorganic and organic including chemical physical and biological met hods. Journal of Analytical Atomic Spectrometry. The development and analytical application of atomic spectrometric techniques including ICP MS. Journal of Chemical Research. All areas of chemistry. The format of this journal (one- or two-page printed synopsis in Part S plus microform version of authors’ full text typescript in Part M) makes it particularly suitable for papers containing lengthy experimental sections or extensive data tabulations. 1.3 Procedure Each manuscript is considered independently by two referees.The referees’ reports constitute recommendations to the appropriate Editorial Board which is empowered to take final action on manuscripts submitted. The Editor acting for the Editorial Board is responsible for all administrative and executive actions and is empowered to accept or reject papers. It is the Editor’s duty to see that as far as possible agreement is reached between authors and referees; although the referees may need to be consulted again concerning an author’s reply to comments further refereeing will be avoided as far as possible. 1.3. I Adjudication of disagreements. If there is a notable discrepancy between the reports of the two referees or if the difference between authors and referees cannot be resolved readily a third referee may be appointed as adjudicator.In extreme cases differences may be reported to the appropriate Editorial Board for resolution. When a paper is recommended for rejection by referees the Editor will inform the authors and return the top copy of the manuscript. Authors have the right to appeal to the Editorial Board if they regard a decision to reject as unfair. The Editor may refer to the Editorial Boards any papers which have been recommended for acceptance by the referees but about which the Editor is doubtful. 1.3.2 Anonymity. The anonymity of referees is strictly preserved and reports should be couched in terms which do not disclose the identity of the writer. A referee should never communicate directly with an author unless and until such action has been sanctioned by the Society through the Editor.1.3.3 Confidentiality. A referee should treat a paper received for assessment as confidential material. Information acquired by a referee from such a paper is not available for citation until the paper is published.REFEREEING PROCEDURE AND POLICY (1 994) 1.4 Policy The primary criterion for acceptance of a contribution for publication is that it should advance scientific knowledge significantly. Papers that do not contain new experimental results may be considered for publication only if they either reinterpret or summarise known facts or results in a manner presenting an advance in chemical knowledge. Papers in interdisciplinary areas are acceptable if the chemical content is considered satisfactory.Papers reporting results regarded as routine or trivial are not acceptable in the absence of other desirable attributes. Although short papers are acceptable the Society strongly discourages the fragmentation of a substantial body of work into a number of short publications; such fragmentation is likely to be grounds for rejection. The length of an article should be commensurate with its scientific content; however authors are allowed every latitude (consistent with reasonable brevity) in the form in which their work is presented. Figures and flow-charts can often save space as well as clarify complicated arguments and should not be excised unless they are unhelpful or really extrava- gant. If a paper as a whole is judged suitable for the Journal minor criticisms should not be unduly emphasised. It is the responsibility of the Editor to ensure the use of reasonably brief phraseology and to assist the author to present his work in the most appropriate format.However referees should not hesitate to recommend rejection of papers which appear incurably badly com- posed. It should be clearly understood that referees’ reports are made in confidence to the Editor at whose discretion comments will be transmitted to the author. To assist the Editor referees are requested to indicate which comments are designed only for consideration as distinct from those which in the referee’s view require specific action or an adequate answer before the paper is accepted. Referees may ask for sight of supporting data not submitted for publication or for sight of a previous paper which has been submitted but not yet published.Such requests must be made to the Editor not directly to the author. I .4. I Authentication of new compounds. Referees are asked to assess as a whole the evidence in support of the homogeneity and structure of all new compounds. No hard and fast rules can be laid down to cover all types of compounds but the Society’s policy is that evidence for the unequivocal identification of new compounds should wherever possible include good elemental analytical data; for example an accurate mass measurement of a molecular ion does not provide evidence of purity of a compound and must be accompanied by independent evidence of homogeneity. Low-resolution mass spectrometry must be treated with even more reserve in the absence of firm evidence to distinguish between alternative molecular formulae.Where elemental analytical data are not available appropriate evidence which is convincing to an expert in the field may be acceptable. Spectroscopic information necessary to the assignment of structure should normally be given. Just how complete this information should be must depend upon the circumstances; the structure of a compound obtained from an unusual reaction or isolated from a natural source needs much stronger supporting evidence than one derived by a standard reaction from a precursor of undisputed structure. Referees are reminded of the need to be exacting in their standards but at the same time flexible in their admission of evidence.It remains the Society’s policy to accept work only of high quality and to permit no lowering of standards. 1.5 Titles and Summaries Referees should comment on titles and summaries with the following points in mind. Titles of papers are used out of context by several organizations for current awareness purposes. To enable such systems to serve chemists adequately titles must be written around a sufficient number of scientific words carefully chosen to cover the important aspects of the paper. Summaries should preferably be self-contained so that they can be understood without reference to the main text. 1.6 Speed of Refereeing The Editorial Boards are anxious to maintain and to reduce further if possible the publication times now being achieved. In this connection referees should submit their reports with the minimum of delay or return manuscripts immediately to the Editor if long delay seems inevitable. 1.7 Suggestions of Alternative Referees The Editor welcomes suggestions of alternative referees competent to deal with particular subject areas.Such suggestions are particularly helpful in cases where referees consider themselves ill-equipped (in terms of specialist knowledge) to deal with a specific paper and in highly specialized or new areas of research where only a limited number of experts may be available. If in such a case the alternative and the original referee work in the same institution the manuscript may be passed on directly after informing the Editor. 1.8 Short Papers and Letters ‘Short Papers’ are published in J.Chem. Research. They are intended for the description of essentially complete pieces of work which can be described in two printed pages or less. They are NOT preliminary communications nor in any way an alternative to Chemical Communications for which there are additional criteria of novelty and urgency. The quality of material contained in a short paper should be the same as that in a full paper. Investigations arising out of some larger project but not prosecuted to the same degree are particularly appropriate for this format. A short paper should not normally exceed in length about 8 pages of typescript including figures tables etc. It should comprise a one-sentence abstract and discussion but adequate experimental details are required.As a consequence of its length it appears in full in Part S with no microform version in Part M. ‘Letters’ published only in Dalton Transactions are a medium for the expression of scientific opinions and views normally concerning material published in that journal; it is intended that contributions in this format should be published rapidly. The letters section is for scientific discussion and is not intended to compete with media for the publication of more general matters such as Chemistry in Britain. Only rarely should a Letter exceed one printed column in length (about 1-2 pages of typescript). Where a letter is polemical in nature and if it is accepted a reply will be solicited from other parties implicated for consideration for publication alongside the original letter.1.9 Relationship with Communications Journals In cases where a preliminary report of the work described has appeared (for example in Chemical Communications) referees should alert the editor to any excessive and unnecessary repetition of material; this can arise in connection with communications journals in which the restrictions on lengthREFEREEING PROCEDURE AND POLICY (1994) and the reporting of experimental data are less severe than those of Chemical Communications. Furthermore the acceptability of the full paper must be judged on the basis of the significance of the additional information provided as well as on the criteria outlined in the foregoing sections. 2.0 Contributions to Chemical Communic- ations Chemical Communications is intended as a forum for preliminary accounts of original and significant work in any area of chemistry that is likely to prove of wide general appeal or exceptional specialist interest. Such preliminary reports should be followed up in most cases by full papers in other journals providing detailed accounts of the work.It is Society policy that only a fraction of research work warrants publication in Chemical Communications and strict refereeing standards should be applied. The benefit to the reader from the rapid publication of a particular piece of work before it appears as a full paper must be balanced against the desirability of avoiding duplicate publication. The needs of the reader not the author must be considered and priority in publication should not be allowed to determine acceptability.Acceptance should be recommended only if in the opinion of the referee the content of the paper is of such urgency that rapid publication will be advantageous to the progress of chemical research. The length of Communications is strictly limited; only in exceptional circumstances should it exceed one printed page (two-and-a-half to three A4 pages of typescript) and referees should be particularly critical of manuscripts longer than this. Communications do not contain extensive spectroscopic or other experimental data but referees may ask for sight of such data before reaching a decision. The refereeing procedure for Communications is the same as that for full papers except that rapidity of reporting is crucial in order to maintain rapid publication.3.0 Communications submitted to Analytical Proceedings and J. Anal. At. Spectrom. Criteria for acceptance of communications submitted to Analytical Proceedings and J. Anal. At. Spectrom. are similar to those for contributions to Chemical Communications except that they should be concerned specifically with analytical chemistry. A decision whether or not to publish rests with the Editor who will obtain advice from at least one referee. 4.0 Communications submitted to Perkin Dalton or Faraday Transactions or J. Mater. Chem. Criteria for acceptance of Communications submitted to Perkin Dalton or Faraday Transactions or J. Mater. Chem. are similar to those for contributions to Chemical Communications except that the work will be of more specialist interest.For Perkin and Dalton Communications inclusion of key experi- mental data is expected. Assessment is carried out by a small nucleus of referees consisting largely of members of the appropriate Editorial Boards. 5.0 Contributions to Mendeleev Communic- ations Mendeleev Communications published jointly by the Royal Society of Chemistry and the Russian Academy of Sciences is a sister publication to Chemical Communications containing preliminary reports of the same type in any area of chemistry. The majority of contributions are from Russian authors. Assessment involves two stages of refereeing. Manuscripts submitted to the Moscow Editorial Office are refereed initially by a Russian scientist. If found acceptable they are then reviewed by Western scientists chosen by the Royal Society of Chemistry.Manuscripts submitted to the UK Editorial Office undergo this two-stage refereeing process in reverse. 6.0 X-Ray Crystallographic Work 6.1 All papers containing crystallographic determinations will be refereed by two referees one a structural chemist. If the editor considers it advisable the paper may also be sent to a specialist crystallographer for comment. Referees will not normally be expected to check values of structural parameters for publication (e.g. bond lengths and angles against atomic co- ordinates; this will be done after publication by the appropriate crystallographic data centre) but should still pay attention to the quality of the experimental crystallographic work. However their primary concern should be such new chemistry as is involved in the structure.6.2 Papers will often contain the information in their titles that an X-ray structure determination has been carried out. However this is not obligatory especially if the X-ray determination forms only a minor part. Summaries should normally contain this information. 6.3 A structure referred to in a Communication will normally be fully refined. The Communication can then be considered to fulfil the archival function and the structure determination may not require further detailed refereeing when presented as part of a full paper. In the full paper the author’s purpose will then be served by a simple reference back to the original communication. However if the crystallography is discussed again at any length in the full paper the data should be re-presented to the referees in full and re-published if considered necessary. 6.4 There may be other cases when an author wishes to publish a full paper in which the result of a crystal structure determination is discussed but in which details or extensive discussion are considered unnecessary. The crystallographer may even be omitted as a co-author (for example when the determination is carried out by a commercial company). If the author is able to show the referees that this procedure is appropriate it will be allowed provided that it does not lead to unnecessary fragmentation. However the author must provide as supplementary information sufficient data relating to the crystal structure determination to allow a referee to make sure that the point made is correct and co-ordinates etc. will be deposited. The brief published description of the determination should be supplemented by appropriate reference to ‘unpub- lished work’ .

ISSN:0267-9477    

DOI:10.1039/JA994090X010

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 11 Silicon Measurement in Bone and Other Tissues by Electrothermal Atomic Absorption Spectrometry Huang Zhuoer Guangzhou Environmental Monitoring Center Guangzhou 5 10030 People's Republic of China A method for the determination of silicon in bone and soft tissues using electrothermal atomic absorption spectrometry is described. Small wet biopsy samples are digested with concentrated nitric acid at 90 "C. The atomization signal of silicon in pyrolytic graphite coated graphite tubes is markedly enhanced by the addition of a lanthanum-calcium mixture in the test solution. No L'vov platform was used. Ammonium dihydrogenphosphate is added to the soft tissue digestate solution to eliminate the interferences arising from the biological matrices while tartaric acid disodium salt is used as a chemical modifier for the analysis of bone digest.Concentrations of silicon in the test solutions are determined against an aqueous standard calibration curve. The characteristic mass is 37 pg (integrated absorbance signal equal to 0.0044 s). For the sample digestion liquids the within- and between-run relative standard deviations are < 5.5%. The accuracy of the method is evaluated by determining the recovery of silicon added to the sample solutions and the results are close to 100%. The detection limits for silicon in bone and other tissues are 0.90 and 0.14 pg g-' wet mass respectively. Examples of silicon contents found in bone brain kidney liver spleen and heart of laboratory rats are given.Keywords Silicon; bone and soft tissues; chemical modifier; electrothermal atomic absorption spectrometry After the work of Carlislel and Schwarz and MilneY2 the biological effects of silicon in humans have been under investi- g a t i ~ n ~ particularly in chronic haemodialysis and patients with Alzheimer's disease.+'' It has been demonstrated that silicon levels are elevated in plasma and various tissues in patients with chronic renal failure on haemodialysis.4-8 In Alzheimer's disease aluminium and silicon were found to be co-localized within tangle-bearing neurons and senile plaque c o r e ~ . ~ * ~ ' Some workers have focused attention on the chemis- try of aluminium and silicon associated with the neurological d i s e a ~ e . ' ~ . ~ ~ Some articles have been published on the effect of silicon deficiency on the mineral composition of bone14 and the role of silicon in medicine and biology." With this background it is necessary to measure silicon in biological fluids and tissues in order to study the biological and toxic effects of this element in man and experimental animals.In the literature several methods have been available for the determination of silicon in serum and urine,16" but only a few procedures have dealt with the measurement of this element in t i s s ~ e s . ~ . ~ ~ ~ ~ ~ Determination of silicon in tissues by d.c. arc atomic emission spectroscopy4 or neutron activation analysis20.21 suffers from high detection limits and high relative standard deviation. In addition the radiochemical methods have the drawback of requiring special chemical separation schemes to remove the interfering activities from the other major elements present in the samples.In the past decade the general approach to silicon examination in tissues has been utilization of various micro-techniques including electron probe X-ray microanalysis,22 scanning electron microscopy and energy dispersive X-ray a n a l y s i ~ ~ ~ ' ~ ~ ~ - ~ ~ and imaging ion micro~copy.~~ Although X-ray microanalysis is considered to be specific for the presence of silicon and has been used effectively to localize this element in it is difficult in its present state of development to obtain reliable results for the silicon content of tissue specimens. Electrothermal atomic absorption spectrometry (ETAAS) has become the method of choice for the determination of silicon in biological fluids'618 and should be considered for use in measuring this element in bone and soft tissues.Nevertheless by contrast with serum and urine various tissue specimens need to be digested to produce sample solutions prior to analysis by ETAAS. In the recent past several wet digestion methods have been used for pre-treatment of tissue sample^.^^^^ However little has been published on sample digestion for the determination of silicon in bone and soft tissues. On the other hand the tissue digestion liquids still contain complex organic and inorganic constituents that can severely interfere with the determination of silicon by ETAAS. The method presently developed for determining silicon in serum and urine33 could not be employed immediately in the analysis of tissue digestion solutions especially in the bone digestion samples owing to the presence of suppressive inter- ferences.This paper describes an improved method of sample preparation for accurate determination of trace amounts of silicon in biopsy samples by ETAAS. Experimental Apparatus All the measurements were carried out on a Perkin-Elmer Zeeman 3030 atomic absorption spectrometer equipped with an HGA-600 graphite atomizer an AS-60 autosampler an Anadex Silent Scribe printer and pyrolytic graphite coated graphite tubes. The hollow cathode lamp for silicon was used at a working current of 30 mA 251.6 nm spectral line and 0.2 nm bandwidth. Argon was used as the purge gas. Sample aliquots (30 pl) were injected into the furnace for analysis.The furnace programme is presented in Table 1. Signals were pro- cessed in the peak area mode. Materials and Reagents No glassware was used and doubly distilled water was used throughout the work. Polystyrene tubes (6 or 12 ml) poly- styrene sample cups and automatic pipettes with disposable Table 1 in tissue digestion solution Temperature programming of furnace for analysis of silicon Gas flow Step TemperaturerC Ramp time/s Hold time/s rate/ml min-' 1 120 5 50 300 2 160 5 5 300 3 400 5 5 300 4 1400 10 30 300 5 2500 0 2 0 6 2700 1 3 30012 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 tips were used. All reagents used were of analytical-reagent grade or better. The silicon stock standard solution (1000 mg 1-I) as ammonium hexafluorosilicate in water was obtained from J.T. Baker (Phillipsburgh NJ USA). Diluents Three diluent solutions were prepared with constituents as follows (per litre) (1) 30 mg of La [as La(NO,),] 30 mg of Ca (as CaCl,) 1.5 g of NH4H2P04 0.5 g of Na,EDTA and 1 ml of concentrated nitric acid; (2) 30 mg of La 30 mg of Ca 10 g of NH4H2P04 and 0.5 g of Na,EDTA; and (3) 30 mg of La and 5 g of tartaric acid disodium salt. The diluents ( l ) (2) and (3) were used for the preparation of standards the dilution of soft tissue and bone digestion liquids respectively. These solutions have no effects on the absorbance value of blank or silicon-containing solutions. Contamination Control Because silicon is ubiquitous in the environment it is important to avoid contamination when dealing with samples.All items utilized during sample collection digestion and analysis were checked for contamination with silicon. Disposable 6 ml poly- styrene tubes and sample cups were rinsed with doubly distilled water and dried before use. The pipette tips used for dispensing sample solution were rinsed twice with water and then with sample solution once. Sample Collection and Digestion Samples were obtained from male Wistar rats (body mass 400-45Og) fed in an animal experiment as a control group. The animals were killed and the tissues were removed and washed with doubly distilled water and then weighed and stored in stoppered polystyrene tubes at -20°C prior to analysis. Bone samples were de-fatted with methanol and chloroform after removing the marrow with a strong stream of distilled water.Throughout the work great care was taken to avoid contamination. A wet digestion procedure was employed in destroying the sample tissues prior to analysis by ETAAS. In brief bone specimens (0.1-0.2 g) and soft tissue samples (0.5-1.0 g) were digested with 1 ml of concentrated nitric acid in the polystyrene tubes with screw caps for 4-6 h in an oven at 90°C. Screw caps were pierced with a needle to allow nitrous vapours to escape. The clear digest was diluted to 10 ml with water and then stored at 4 "C. Analytical Procedure Before analysis the sample digestion liquids were further diluted with the relevant diluents. Silicon was measured in soft tissue digestion liquids after 10-fold dilution with diluent (2) whereas the bone digestion solution was diluted 30-fold with diluent (3).The concentrations of silicon in the diluted samples were calculated against a calibration curve prepared by diluting the standard in diluent (1). An intermediate standard containing 200 pg 1-' of silicon was prepared by diluting the stock stan- dard with water. Working standards containing 0 10 20 50 and 100 pg 1-1 of silicon were prepared by diluting the inter- mediate standard with diluent (1). At the beginning of the analysis by ETAAS a blank solution i.e. diluent ( l ) was run 5-8 times to obtain a low and reproducible absorbance value and the spectrometer was zeroed on this value. A pyrolytic graphite coated graphite tube can be used for up to approximately 180 firings with stable sensitivity of the silicon measurement but aged tubes (above 220 firings) would encounter more matrix interference.Results and Discussion Sample Digestion The digestion procedure is an important step in trace element analysis of tissue by ETAAS. According to some biological samples can be digested with nitric acid at tempera- tures of 60-105 "C. In sample digestion for the determination of aluminium however Blotcky and Claa~en,~ have warned of A12C16 subliming from the digested sample matrix at tempera- tures above 80 "C. Precautions against analyte loss should therefore be taken with sample digestion for the determination of silicon in bone and soft tissues. With the proposed digestion procedure no loss of silicon was observed during sample digestion.Water bone and other samples with or without the addition of 5.0 or 10.0 pg of silicon respectively (in 50 pl of aqueous standards) were digested with 1 ml of nitric acid to evaluate the effects of digestion temperatures of 60 70 80 90 and 100 "C on the recovery of added silicon. Analytical recover- ies of added silicon in various biological materials (including bone brain kidney liver spleen and heart) were in the range 98-105% independent of the digestion temperatures tested suggesting that the proposed wet digestion method is suitable for the determination of silicon in bone and other tissues. Instrument Settings The optimum furnace temperature programme for the determi- nation of silicon in bone and other tissues is summarized in Table 1. It is our experience that a charring step at 400°C is necessary to obtain reproducible absorbance values for the same test sample.At this temperature the sample residue after drying could be scorched without sputtering. In the presence of lanthanum and calcium a pyrolysis step at 1400°C for 30 s is sufficient to obtain the maximum absorbance value for a given amount of silicon. The optimum temperature for atomiz- ation was found to be 2500°C. Matrix Interference and Chemical Modification Because of the extremely low levels of silicon in bone and soft tissues digested samples containing relatively high concen- trations of biological matrices are required to attain sufficient concentrations of the analyte. This causes serious problems in the analysis of the digest by ETAAS owing to severe matrix effects.Soft tissues During development work it was found that the presence of tissue matrices resulted in poor sensitivity and poor precision. These interferences are mostly caused by organic matrices which have not been completely destroyed after the digestion process. Although the mixture of lanthanum and calcium has been confirmed to be an excellent chemical modifier for the atomization of silicon in a graphite atomizer,33 interferences from the tissue matrices could not be eliminated by the addition of this mixture to samples. Consequently another chemical modifier must be used. In the determination of silicon in serum by ETAAS ammonium dihydrogenphosphate has been used effectively as a chemical modifier to eliminate interferences from organic matrices.33 This phosphate is also an efficient chemical modifier for use in the measurement of silicon in the digestate of soft tissue by ETAAS and the degree of modifi- cation is directly proportional to the concentrations of the phosphate in the test solutions.With a concentration of 1% m/v of ammonium dihydrogenphosphate the diluted sample containing 10 mg ml-I of tissue matrix can be determined for silicon with no matrix effects. Bone The bone digestate solution contains a high concentration of calcium phosphate. In analysis by ETAAS the presence ofJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 13 considerable amounts of phosphate residue after drying gives rise to the risk of sputtering during thermal treatment. On the other hand incomplete decomposition of the sample matrices before atomization results in suppressive interferences on the silicon signal.Fig. l(b) and (c) shows the shapes of the atomiz- ation signals obtained by silicon added to digested bone samples with the addition of lanthanum. Clearly the bone matrix suppresses the silicon atomization signal and part of the signal is shifted to a higher temperature if the concentration of bone matrix in the solution is rather high. According to the chemistry of silicate and phosphate silicate can enter the phosphate particles in a molten state when treating a mixture of silicate and phosphate at high tempera- tures. Thus it is possible that the interference effect of bone matrix is due to the interaction of calcium phosphate (in considerable amounts) with silicate to form polycompounds (for example phosphorosilicate glass).The phosphorosilicate polycompounds are rather stable at high temperature ( 1400 "C) and have not been dissociated completely before the atomiz- ation cycle resulting in a suppression effect on the silicon atomization signal. Although ammonium dihydrogenphosphate is a good chemi- cal modifier for the determination of silicon in many biological materials by ETAAS as discussed above it is less useful for the digested bone samples. Indeed a suppressed silicon signal will be observed if the concentration of calcium in the test solution is higher than 60mg1-' (in the presence of pho~phate).~~ Previously in the determination of trace elements in sea- 0.5 ( b ) I 0.5 Q) ( C) P 4 0.25 I ( d ) 1 .o 1 0.5 I A 0 \ 0 1 .o Ti m e/s 2.0 Fig.1 Comparison of atomization signals obtained for 100 pg 1-' of Si (20 pl) added in water and bone digestion samples with the addition of 40 mg 1-l of La. (a) Aqueous solution containing 40 mg 1-' of Ca.; (b) and (c) diluted solutions containing 0.66 and 2.5 mg ml-' of bone matrix respectively; and ( d ) and (e) diluted solutions containing 0.66mgml-' of bone matrix with the addition of 1.0% m/v of Na4EDTA and 0.5% m/v tartaric acid disodium respectively. Values for the integrated signals are (a) 0.240; (b) 0.128; (c) 0.133; ( d ) 0.211; and (e) 0.261 s water by ETAAS it has been confirmed that the addition of some hydroxyl-acids can eliminate the suppressive interferences from high salt matrices.34 In the present study tartaric acid disodium salt Na,EDTA citric acid ascorbic acid and ammonium acetate were tested in order to examine their effects on the atomization of silicon added in bone digestate in the furnace in the presence of lanthanum.The results indicated that only the tartaric acid and EDTA salts among the reagents tested could substantially enhance the absorbance signal for silicon added in the digested bone samples. The shapes of silicon signals obtained in these instances are shown in Fig. 1 ( d ) and (e). From these figures it can be seen that the suppression effect of bone matrix on the silicon signal is eliminated by the addition of tartaric acid disodium or Na,EDTA but the signal obtained with the addition of tartaric acid disodium is more regular than that with the addition of Na,EDTA.On the other hand Fig. 2 presents the effects of the concentrations of these two reagents on the sensitivity of silicon measurement in bone digestion solution. The suitable concentrations of Na,EDTA in the sample solutions are in the range of 2-3% m/v whereas 0.5-4% m/v of tartaric acid disodium salt can be used with a higher sensitivity of silicon measurement. These results together indicate that tartaric acid disodium salt is superior to Na,EDTA in the modification effect on bone matrix. The concentration of 0.5% m/v of tartaric acid disodium salt in the diluted samples was selected in order to obtain a negligible blank value. Under this condition the diluted sample contain- ing up to 1.0 mg ml-' of bone matrix can be determined with quantitative recoveries of added silicon. With the observation mirror it was found that the residue of sample solution after drying in the presence of tartaric acid disodium salt or Na,EDTA was scorched at temperatures ranging from 350 to 400 "C and considerable amounts of foam materials were produced during this process.In contrast no similar phenomenon was observed when either citric acid ascorbic acid or ammonium acetate was added to the test solution. From these observations it is believed that the above mentioned modification effect is partly associated with the presence of foam materials during the charring process of organic reagents. The effect of tartaric acid disodium salt or Na,EDTA can be attributed mostly to the complexing reaction of the majority of calcium in the bone digest with the organic reagent instead of with PO or Si03.On the other hand the presence of foam materials during thermo-treatment can prevent the formation of refractory polyphosphates. The combination of these factors leads to the elimination of suppressive interferences from the bone matrix on the determination of silicon by ETAAS. Calibration Sensitivity and Detection Limits With the use of suitable chemical modifiers a variety of biological samples can be analysed for silicon by ETAAS with no interferences and aqueous standards can be used for (0 0.15 \ 1 0 (D e n P 0.10 m U CI E 0.05 e I A L - I I I I 0 1 2 3 4 Concentration (% w/v) Fig. 2 Effects of the concentrations of A tartaric acid disodium salt or B Na4EDTA on the sensitivity of silicon measurements (50 pg 1- of Si 20 pl) in the bone digestion samples (0.66 mg ml-' of bone matrix) containing 40 mg 1-' of La14 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL.9 Table 2 Precision for determinations of silicon in bone and soft tissue digestion samples; results given as mean f SD Matrix concentration$/ Tissue mg ml-' Bone 1 0.66 2 0.42 3 0.58 Brain 1 5.3 2 6.2 3 4.8 Liver 1 6.9 2 5.8 3 4.4 Kidney 1 7.2 2 5.1 3 5.6 Within-run* Between-day? CSiISi 1- 9.0 1- 0.3 21.5 k 0.7 42.1 k 1.1 6.5 f 0.2 58.2 k 1.6 105f2.1 10.8 f 0.3 58.1 f 1.3 105? 1.2 16.2 t- 0.6 60.1 f 1.0 111 f 1.8 RSD(%) 3.3 3.3 2.6 3.1 2.7 ' 2.0 2.8 2.2 1.1 3.7 1.7 1.6 [Silt:' Pg 1- 9.1 f0.4 21.8f 1.2 41.8f 1.6 6.6 f 0.3 58.1 f 1.9 106 -t 2.8 11.0 & 0.4 57.8 f 2.3 106 & 2.6 16.5 f 0.8 59.3 f 1.3 112 f 2.8 RSD(%) 4.4 5.5 3.8 4.5 3.3 2.6 3.6 4.0 2.5 4.8 2.2 2.5 * n=10.t n=3 d = 10. 1 In the test solution. 9 1 no Si was added; 2 and 3 5.0 and 10.0 pg of Si were added to the samples before digestion respectively. calibration purposes. This was confirmed by a comparison of the values of the characteristic mass (m,) calculated from the slopes of the standard additions graphs in various biological matrices including bone brain liver lung heart kidney and spleen with that from a calibration graph for the aqueous standards. The measured values of rn were the same as that obtained for silicon in serum and urine,33 i.e. 37 pg gave an integrated absorbance signal with a net area of 0.0044s suggesting that the determinations were completely interference free.In all instances the calibration graphs were linear up to 200 pg 1-l of silicon in diluted solutions. Since the blank values of the diluents used for the prep- aration of standards and the dilution of tissue digestion liquids are negligible and the sensitivity of the silicon measurement in all instances are the same it is not necessary to match the concentrates of chemical modifiers in the standard and sample solutions. In addition the diluent used for the preparation of standards can also be used for the dilution of serum and urine samples33 and the latter diluted samples can be determined for Si against the same calibration graph as used in the present study. The detection limits (3a n= 10) for silicon in the diluted solutions of bone and other tissue digestion liquids were 0.6 and 0.7 pg l-' respectively corresponding to 0.90 and 0.14 pg g-' of silicon in the initial wet specimens of bone (0.2 g) and other soft tissues (0.5 g) respectively.These results were obtained by repeatedly measuring the same diluted solution in each case. These detection limits are low enough for the determination of silicon in biopsy samples. Precision and Accuracy Precision data for the determination of silicon in various biological materials are given in Table 2. The within-run and between-day variations were calculated from the results deter- mined for the sample digestion liquids and the standard spiked liquids over a period of 1 month. The variations are satisfactory at the concentrations studied.The accuracy of the method was more difficult to assess because there was no appropriate reference material available with a certified value for silicon in tissues. Nevertheless the recoveries of silicon added to various tissue specimens have been determined. Analytical recoveries were close to 100% (Table 3). Silicon Contents in Tissues of Laboratory Rats Using the proposed procedure the silicon contents in bone brain kidney liver spleen and heart samples from four labora- Table3 Analytical recovery of silicon added in bone and soft tissue digestion samples Range of matrix Tissue concentration*/mg ml- ' Recovery( YO)? Bone 0.48-0.96 99.2 1.7 Kidney 5.2- 10.1 101 2 1.4 Liver 5.8-9.8 loo+ 1.5 Spleen 5.5-10.2 101 1.6 Brain 4.6- 8.8 1002 1.2 Heart 6.2-9.6 look 1.0 * In the test solution. 7 Mean+SD determined by adding 10.0 or 20.0 pg 1-' of Si to the diluted samples and then reading the concentrations from an aqueous calibration curve; n = 6.tory rats were determined. The results are listed in Table 4. Although the number of animals tested is too limited to perform statistical analysis significant differences could be seen between the mean silicon levels in selected tissues. Briefly the highest concentration of silicon was found in the bone whereas the brain contained the lowest silicon content. Such a result is in agreement with those of previous studies on rats using ~ i l i c o n - 3 1 . ~ ~ ~ ~ Since the laboratory male rats were from the same control group batch in the animal experiment the animal- to-animal variance in the tissue silicon content shown in Table4 is normal and unlikely to be attributable to the analytical error.Conclusions The ETAAS technique provides a sensitive precise and accu- rate method for determining silicon in biological materials even at the extremely low concentrations found in bone and soft tissue specimens. The mixture of lanthanum-calcium- phosphate is a very specific chemical system that can be used Table 4 Silicon levels found in tissues of laboratory rats. Duplicate samples were determined for each tissue; results given in pg g-' of wet mass Animal No. Bone Brain Kidney Liver Spleen Heart 1 13.6 1.23 1.55 1.57 1.75 1.30 2 12.9 1.21 2.71 1.72 1.92 1.27 3 10.9 1.04 2.25 1.26 1.69 1.52 4 13.8 1.24 1.96 1.38 1.56 1.46 Mean value 12.8 1.18 2.12 1.48 1.73 1.39JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL.9 15 effectively as the chemical modifier for the determination of silicon in various biological materials by ETAAS after nitric acid digestion or direct dilution (the digestion step is not necessary for serum and urine samples33). For the bone digest in addition it is necessary to add tartaric acid disodium salt to the test solution for the purpose of chemical modification. With the proposed procedure direct aqueous calibration is possible. The detection limits of the method described here are low enough for the determination of trace amounts of silicon in tissues and the method can be employed in the study of silicon metabolism in various organs. The author thanks Kim Solvang for her considerable editorial assistance in the preparation of this manuscript.1 2 3 4 5 6 7 8 9 10 11 12 13 References Carlisle E. M. Science 1972 178 619. Schwarz K. and Milne D. B. Nature (London) 1972 239 333. Silicon Biochemistry Ciba Foundation Symposium 121. Wiley Chichester 1986. Indraprasit S. Alexander G. V. and Gonick H. C. J. Chronic Dis. 1974 27 135. Mauras Y. Riberi P. Cartier F. and Allain P. Biomedicine 1980 33 228. Adler A. J. and Berlyne G. M. Nephron 1986 44 36. Hosokawa S. Morinaga M. Nishitani H. Maeda T. and Yoshida D. Trans. Am. Soc. Artif. Intern. Organs 1987 33 260. Gitelman H. J. Alderman F. R. and Perry S. J. Am. J. Kidney Dis. 1992 19 140. Perl D. P. and Brody A. R. Science 1980 208 297. Candy J. M. Oakley A. E. Klinowski J.Carpenter T. A Perry R. H. Atack J. R. Perry 2. K. Blessed G. Fairbairn A. and Edwardson J. A. Lancet 1986 1(8477) 354. Edwardson J. A. Oakley A. E. Taylor G. A McArthur F. K. Ward M. K. Bishop H. P. and Candy J. M. Adv. Neurol. 1990 51 223. Birchall J. D. and Chappell J. S. Clin. Chem. 1988 34 265. Bilinski H. Horvath L. and Tybojevic-Cepe M. Clin. Chem. 1992 38 2019. 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Brossart B. Shuler T. R. and Nielsen F. H. Proc. N.D. Acad. Sci. 1990 44 95. Dobbie J. W. Scott. Med. J. 1982 27 1 . Berlyne G. M. and Caruso C. Clin. Chim. Acta. 1983 129 239. Gitelman H. J. and Alderman F. R. J . Anal. At. Spectrom. 1990 5 687. Holden A. J. Littlejohn D. and Fell G. S. Anal. Proc. 1992 29 260. Roberts N. B. and Williams P.Clin. Chem. 1990 36 1460. Velandia J. A. and Perkons A. K. J. Radioanal. Chem. 1974 20 715. Guzzi G. Pietra R. and Sabbioni E. J. Radioanal. Chem. 1976 34 35. McClure J. and Smith P. S. J. Pathol. 1984 142 293. Goligorsky M. S. Chaimovitz C. Nir Y. Rapoport J. Kol R. and Yehuda J. Miner. Electrolyte. Metab.. 1985 11 301. Funahashi A. Schlueter D. P. Pintar K. and Siegesmund K. A. Br. J. Int. Med. 1988 45 14. Jennings D. A. Morykwas M. J. Defranzo A. J. and Argenta L. C. Ann. Plast. Surg. 1991 27 553. Schmitt J. Dietzmann K. and Von-Bossanyi P. Acta Histochem. Suppl. 1992 42 319. Landis W. J. Lee D. D. Brenna J. T. Chandra S. and Morrison G. H. Calcif. Tissue Int. 1986 38 52. Bonilla E. Clin. Chem. 1978 24 471. D’Haese P. C. Van de Vyver F. L. De Wolff F. A and De Broe M. E. Clin. Chem. 1985 31 24. Van Ginkel M. F. Van der Voet G. B. and De Wolff F. A. Clin. Chem. 1990 36 658. Anderson J. R. and Reimert S. Analyst 1986 111 657. Blotcky A. J. and Claassen J. P. Anal. Chem. 1992 64 2910. Huang Z. E. Clin. Chem. submitted for publication. Zhang Z. X. Huang Z. E. Li G. K. and Yang X. H. Bull. Anal. Test. (Chinese) 1991 10(4) 1. Mehard C. W. and Volcani B. E. Bioinorg. Chem. 1975 5 107. Adler A. J. Etzion Z. and Berlyne G. M. Am. J. Physiol. 1986 251 E670. Paper 310341 5 A Received June 14 1993 Accepted August 31 1993

ISSN:0267-9477    

DOI:10.1039/JA9940900011

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

FACSS What is FACSS? FACSS is the Federation of Analytical Chemistry and Spectroscopy Societies organized to sponsor annual conferences in the field of analytical chemistry. FACSS is a nonprofit organization governed by a board with representatives fiom six member organizations - the American Chemical Society the Analytical Division (ACS); the Analysis Division of the Instrument Society of America (ISA); the Association of Analytical Chemists (ANACHEM); the Society for Applied Spectroscopy (SAS); the Coblentz Society and the Royal Society of Chemistry (RSC). FACSS conferences rely on a successfil combination of invited and contributed papers workshops and short courses and technical exhibits. The record of achievement is due to FACSS's 20 years of conference experience and to the contributions of scientists fiom the U.S.and abroad. Attendance at the annual meeting includes approximately 1,500 participants who can attend workshops and short courses given by experts in the various areas of analytical chemistry; visit the extensive exhibits of the most up-to-date analytical equipment and materials; select fiom approximately 1,000 papers and poster sessions that are presented throughout the week in parallel sessions; and enjoy sightseeing excursions. FACSS conferences are often called "just the right size," because they are large enough to cover the full range of analytical sciences and small enough to allow participants to talk with individual vendors visit with colleagues and just run into people they want to talk to. FACSS program sessions are recognized as being successfil because they are presented by international leaders in the scientific community fiom academia industry and government covering the wide range of analytical sciences atomic spectroscopy bioanalysis clinical chemistry chemometrics gas and liquid chromatography electrochemistry environmental analysis infiared spectroscopy lasers mass spectrometry nuclear magnetic resonance spectrometry process analysis Raman spectroscopy x-ray spectroscopy and surface analysis.Who should attend? Any individual working in the field of analytical chemistry as a researcher analyst or technician will benefit. In fact many people in the field regard FACSS as the one meeting a year that they can't afford to miss. Where is FACSS held? FACSS conferences are held in cities that also offer other attractions for participants.Meetings have been held in Philadelphia Cleveland Chicago and elsewhere. The 1994 FACSS Conference will be held 2-7 Oct. in St. Louis. How do you get more information? receive the Call for Papers and Preliminary Program please write to the following address To get on the FACSS mailing list and FACSS National Office 198 Thomas Johnson Drive Suite S-2 Frederick MD 21702-4317 (301)846-4797Announcement and Call for Papers Twenty-First Annual Conference of the Federation of Analytical Chemistry and Spectroscopy Societies October 2-7 1994 Cervantes Convention Center St. Louis Missouri John Koropchak Terry Hunter Program Chair General Chair Southern Illinois University Monsanto Corporation (618) 453-6471 (314) 537-6219 FACSS National Office 198 Thomas Johnson Dr.Suite S-2 Frederick MD 21702-43 17 (301-846-4797) Scientific Program and Submission of Papers The FACSS meeting is one of the world's leading conferences in analytxal chemistry with over 1,500 participants and a program comprised of almost 1,000 presentations. This year in addition to sessions on the core topics of atomic and molecular spectrometry chromatography and electroanalysis the meeting will also feature sessions devoted to nanoscale analyses biosensors for the 2 1 st century materials characterization chemical analysis and neuroscience challenges to environmental analysis and issues facing the next generation of analytical scientists. Contributed original research papers are solicited in all areas of analflcal chemistry.Please complete the title submission form and return it by March 21 1994. Submitted papers will either be 20-minute talks or be presented in poster sessions. Upon acceptance of your submission final abstract materials and instructions will be sent to you May 20 1994. Listing of your presentation in the Final Program is contingent upon receipt of your 250-word final abstract via disk submission by July 1,1994. 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Instrument Exhibit The instrument exhibit is one of the more useful and exciting components of the conference and is designed to complement the scientific program.The exhibition area can accommodate 125 booths and will serve as the primary gathering place for many of the social events associated with the conference. Workshops Short Courses and Employment Bureau Workshops and short courses conducted by leading scientists will be offered in conjunction with this conference. Typical topics include ICP-MS GC-MS LC-MS Sample Preparation Statistics Lasers in Analflcal Chemistry and Chemometrics. An Employment Bureau will offer both local and national job listings. In addition workshops on resume preparation and career planning will be available to assist professionals seeking employment.1994 FACSS Conference Title Submission Form Please type or print clearly Title Deadline March 21,1994 (Acceptance of submissions after this date cannot be guaranteed) Topic Code(s) +Title (maximum of 3 fiom Topic Code List below) Authors (underline or circle presenting author) Corresponding Author Information First Name Middle Initial Last Name Company/University Address City State Zip/Postal Code country Phone Fax Phone No.Preferred format* Talk Poster Either 0 * Actual format may be determined by space availability and format of similar talks in your topical area. +Specific references to vendor products in the title of papers will not be permitted. ~ ~ ~~ ~~~~ ~~ ~~~~~ A. Atomic Spectrometry G. Molecular Spectroscopy N. NMR B. BioanalytmdKlinicaV H. Raman 0. Imaging C . Chromatograp hy/Separations J. Flow AnalysidInjection PI FundamentaWTheory D.Process Control/Analysis K. ChemometricdCornputers P2 Applications E. Electroanalytxal L. Luminescence P3 Instnunentation F. Mass Spectrometry M. MaterialdSolid StatdSurfaces P4 Other/Special Pharmaceutical Analyses I. Infrared/Near-Infkared P. Other Sessions Preliminary 100 word brief (PLEASE TYPE) ~ ~ _ _ _ ~ _ _ _ _ _ _ ~ ~ Please send this completed form to FACSS National Oflice P.O. Box 278 (2409 Himes Street for overnight express) Manhattan KS 66502 Note 1 Send completed forms for invitedsolicited talks to the symposium organizer. Note 2 No FAX submissions will be accepted.Registration Form Federation of Analytical Chemistry & Spectroscopy Societies Twenty-First Annual Conference St. Louis Missouri October 2-7 1994 Date cirst Name Miidle Initial Last Name Work Phone Fax Phone No.~~ Ifspouse is attending please provide name so badge can be printed. 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Please apply payment to my Master Card or VISA Credit Card Number Expiration Date Printed name as appears on card Signature FACSS WORKSHOPS The final FACS S Workshop schedule will include Sample Preparation Professional Chemists in Industry Supercritical Fluid Chromatography Chemometrics and ICPMS. Additional work- shops will be listed in the Preliminary Program. Deadline for Preregistration is September 3 1994 Cancellations prior to this date will be subject to a $50 processing charge.No refunds will be given after this date but credit will be given towardr the 1995 meeting fees. FACSS 198 Thomas Johnson Drive Suite S-2 Frederick MD 2 1702 DO NOT MAIL ANY REGISTRATION FORM AFTER SEPTEMBER 17,1994. There will be a reception Sunday evening for those who have preregistered. See Program for details.0 a FACSS XXI Housing Request Form October 2-7 1994 Reservations must be received by the hotel no later than September 1. Reservations made after the cutoff date cannot be guaranteed convention rates. List the names of all persons sharing this room. Submit only one housing form per room. List the names of all persons sharing this room. The hotel acknowledgment will be sent only to the first person named below. Please adhere to the individual policies stated on the hotel confirmation which will be sent to each individual by the hotel two to four weeks prior to the start of the meeting. Please notify the hotel of all changes and cancellations in writing prior to September.Rooms will be held only until 6:OO p.m. unless guaranteed by credit card. Requests for eAxhibitor hospitality suites must be made through the FACSS Arrangement Chair. The Adams Mark Hotel is the headquarters hotel. Name First Name Initial Last Name Sharing Last Name First Name Last Name First Name Ad dress Sneer Address city State zip code Counvy Phone Number Anival Date Time Departure Date Credit Card Type Number Evp. Date Hotel Preferences Single Double r? Adarns Mark Hotel (Headquarters) 0$114 0$124 Fourth & Chestnut Streets Phone 1-3 14-241 -7400 St.Louis. Missouri 63 102 FAX 1-314-241-6618 c! Drury-Gateway Arch 71 1 North Broadway St. Louis Missouri 63102 HolidayInn 81 1 North 9th Avenue St. Louis Missouri 63102 0 $84 n$94 Phone 1-3 14-23 1-5232 FAX 1-314-231-3817 $85 same Phone 1-314-42 1-4000 FAX 1-314-421-5974Federation of Analytical Chemistry and Spectroscopy Socieities Nominations for the Tomas Hirschfeld Student Awards 1994 FACSS Conference October 2-7,1994 Cervantes Convention Center St. Louis A40 Nominations are requested for the Tomas Hnschfeld Student Awards which will be presented at the Twenty-First FACSS Conference. Awards are given for the most outstandmg papers submitted by graduate students in the field of analytical chemistry. The student nominees will present 20 minute papers at the 1994 FACSS Conference. To be considered for these awards students must submit a Call For Paper - Title Submission Fom two letters of nominations including one from their graduate advisor any reprints/preprints and a 250 word abstract to Diane Landoll FACSS National Office P.O. Box 278 Manhattan KS 66502. The deadline for submission of all materials is March 21,1994. Awardees will have their travel arranged and paid for by FACSS. Papers that are not selected for the award will still be scheduled for presentation. If you are unable to attend unless you are an award winner please notify us so we can remove your paper from the Program. For further information concerning the Tomas Huschfeld Student Awards contact the Student Award Chairman Professor S. Roy Koutyohann Univ. of Mssouri-Columbia Dept. of Chemistry 123 Chemistry Bldg. Columbia MO 6521 1 (314) 882-8374

ISSN:0267-9477    

DOI:10.1039/JA994090X013

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 Comparison Between Infrared and Ultraviolet Laser Ablation at Atmospheric Pressure-Implications for Solid Sampling Inductively Coupled Plasma Spectrometry Christian Geertsen* Alain Briand Frederic Chartier Jean-Luc Lacour Patrick Mauchient and Sten SjostromS Laboratoire de Spectroscopie Laser Commissariat a L’Energie Atomique Service de Physique d’Experimentation et d’Analyse Centre d’Etudes de Saclay BSt. 397 9 7 79 7 Gif-sur-Yvette Cedex France. Jean-Michel Mermet Laboratoire des Sciences Analytiques Bit. 308 Universite C. Bernard Lyon 7 69622 Villeurbanne Cedex France. 17 The efficiency of laser solid sampling was investigated as a function of several experimental parameters under experimental conditions similar to those used for laser ablation (LA) inductively coupled plasma spectrometry. This was done by studying the amount of material removed as a function of melting temperature of the (metallic) matrix material laser wavelength and laser energy and by studying the plasma ignition in air and argon buffer gases as a function of laser wavelength.It was found that direct LA is the major process responsible for the removal of material in the case of a UV laser as opposed to with an IR laser where shielding of the laser radiation by the absorbing plasma limits direct LA and increases the temperature of the plasma. The consequences of this difference between IR and UV laser radiation are considerable and lead to a superior performance of UV laser sampling in every analytical aspect reproducibility matrix effects quantification spatial resolution and sensitivity.Keywords Laser-produced plasma; solid sampling; laser ablation; inductively coupled plasma spec- trometry; trace analysis Laser ablation (LA) for direct solid sampling and subsequent analysis was introduced in the early 1960s. This technique presents several important features such as direct analysis of both non-conducting and conducting materials localized lat- eral analysis no sample preparation prior to analysis and operation at atmospheric pressure. However in spite of the important potential of this sampling technique it is only recently that results have been obtained that compare favour- ably with other solid sampling techniques. This is mainly owing to two major developments during the past few years.Firstly the lasers used for laser solid sampling today are more reliable stable and easy to handle than in the past. Secondly the use of inductively coupled plasma mass spectrometry (ICP-MS) for the detection of the ablated material offers a performance previously unmatched in terms of sensitivity time of analysis and ease of use. All commercially available instruments for LA-ICP-MS are equipped with a pulsed Nd:YAG laser operating in the IR at its first harmonic (1064 nm). This choice of laser is based on two essential reasons firstly it is today the cheapest and simplest choice of laser for these kinds of applications and secondly the results of for example Gray’ and Arrowsmith’ have shown that high sensitivities can be achieved typically in the sub-pg g-’ range for solid samples.However in spite of the analytical efforts of numerous laboratories the technique still exhibits an unsatisfactory reproducibility (above loo/,) for many applications. This is for example the case for quality control of many industrial products where a precision of the order of 0.1% is required for the major elements and a few percent for the minor and trace elements. The levels of precision required for trace and minor elements are obtainable by ICP atomic emission spectrometry (AES) if * On leave from the Pechiney Centre de Recherches de Voreppe t To whom correspondence should be addressed. 1 On leave from the Department of Physics Chalmers University BP 27 38340 Voreppe France. of Technology 5-412 96 Sweden.liquid nebulization sample introduction is used. The shot-to- shot stability of the laser itself is of the order of a few percent and averaging over many laser shots should lead to reproduci- bilities of better than 1%. Hence the basis for the moderate accuracy and precision of LA-ICP-MS is to be found in the physics of the laser-surface interaction. The purpose of this paper is to investigate the ablation efficiency as a function of several experimental parameters. This was done by studying the amount of material removed as a function of matrix material laser wavelength and laser energy and by studying the plasma ignition in different buffer gases as a function of laser wavelength. Experiment a1 Three sets of experiments were performed. The experimental arrangement (see Fig.1) for the production of the plasmas consisted of a laser a focusing lens and the target for the first two sets of experiments with the addition of a charge-coupled device (CCD) camera with imaging optics for the third set of experiments. Laser I Lens f= 100 rnm I7 Diaphragm Lens f=25 rnm Plasma camera Fig. 1 Experimental arrangement for LA of solid targets. The intensi- fied charge-coupled device (CCD) camera with imaging optics and the delay unit were used for the registration of the plasma emission in Experiment 318 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 Experiment 1 Several laser sources emitting at different wavelengths were used to determine the ablation efficiency on a copper target in air buffer gas as a function of laser energy and laser wavelength see Fig.1. The laser sources used were the first three harmonics of a Q-switched Nd:YAG (Quantel YG-585-10) and two excimer lasers with XeCl emitting at 308 nm (Lambda-Physik EMG 102 MSC) and with ArF emitting at 193 nm. The laser energy was controlled with a power meter (Scientech 372). The pulse durations were approximately 10 ns for the Nd:YAG and 30 ns for the excimer lasers. The laser beams were incident on the target at normal angle and focused on the target using a plano-convex lens with a focal distance of 100 mm (Suprasil for the UV wavelengths and Herasil for the IR). The focal spot area was approximately 2 x lop4 cm2 for the Nd:YAG and 1 x The ablated mass defined by the displaced volume was measured by integrating the volume of the crater with a high- performance scanning profile-meter (laboratory made).The position of the sample relative to the lens was selected to be that which gave the smallest crater size. cm2 for the excimer lasers. Experiment 2 Several laser sources emitting at different wavelengths were used to determine the ablated mass uersus fusion temperature of several targets in air buffer gas at different wavelengths at a laser energy of 85 mJ per laser pulse corresponding to a fluence of 90 J cmp2 for the excimer lasers and 425 J cmP2 for the Nd:YAG laser. The laser sources used were the first ( 1064 nm) and second (532 nm) harmonics of the Nd:YAG and the XeCl excimer laser emitting at 308 nm. The samples covered a range of melting temperatures from 700 (zinc) to 3700 K (tungsten).The laser beams were focused on the surface in the same way as in Experiment 1. Experiment 3 The role of the buffer gas and the laser wavelength in ignition of the plasma was investigated by means of time-resolved images of the emission from the laser produced plasma. The ablation was performed with the first harmonic (1064 nm) as well as the third harmonic (355 nm) of an Nd:YAG laser (Quantel Compact YG-585-30). The pulse energy was 10mJ per pulse a value commonly encountered in LA,3 and the duration of the laser pulse was 6ns [full width at half maximum (FWHM)]. The energy was adjusted by slightly varying the angle of a dielectric mirror reflecting 100% at 45" and not by adjusting the supply voltage since this changes the energy distribution in the laser beam.The laser beam was focused at right angles onto the surface of the sample using a plano-convex lens with a focal distance of 100 mm. The positioning of the samples was carried out by moving the sample until the highest acoustic levels were found. It is experimentally very easy to determine this position and this method was used rather than the technique described above as the plasma images exhibited the same characteristic features within a range of about 10mm around the optimal sample position. At the first harmonic (1064 nm) it was found that the highest acoustic level was obtained when the laser beam was focused slightly in front of the sample (2mm) whereas the laser was focused on the surface in the case of the third harmonic.The positioning of the sample at the focal point is often done by determining the position where maximum mass is ablated but the proposed method is much simpler and the results obtained by the two methods compare well with one another for UV lasers it is well-known that ablated mass increases with the acoustic ~ i g n a l ~ and for IR lasers we have observed that crater diameters do not change whether the focus is slightly in front of or on the surface of the target. Irradiation areas on the target were determined using the 'knife-edge' m e t h ~ d . ~ For the IR laser radiation the diameter was approximately 150-170 pm (60-80 pm at the focal point) while in the UV the diameter was approximately 100-120 pm. Measurements were made for aluminium and copper targets and were carried out at atmospheric pressure both in air and in argon buffer gas.Images of the plasma were taken with an intensified gated CCD camera (Hamamatsu C4346-Ol) with a gate time of 3 ns at right angles to the laser beam. A biconvex lens with a focal distance of 25mm was used for the imaging of the plasma giving a magnification of 10 x on the CCD. A diaphragm with a diameter of 3 rnm (yielding aroundfll0) ensured that spheri- cal aberrations were small while two colour filters (Schott BG3 and GG400) limited the spectral range to 400-500nm and thus virtually eliminated chromatic aberrations and stopped scattered laser radiation from reaching the CCD detector. Each image was taken after about 1000 laser shots in the same place on the target. This choice was based on earlier findings that the optical emission signal evolves during the first laser shots and is stable thereafte~-.~.~ The CCD camera was triggered from the laser trigger output.A jitter of about 2 ns was measured for this trigger signal. The time delay for image registration was measured relative to the beginning of the laser pulse. The intensity of the light emission is represented by false colours in the images. Results and Discussion In the first set of experiments the amount of material removed from a copper target as a function of wavelength and laser energy was investigated. In Fig. 2 it is shown that the ablation efficiency (ablated mass per unit energy per unit surface) as a function of laser fluence is more than one order of magnitude higher (20 times) for a UV laser than for an IR laser or even a visible laser at 200 J cm-2.It should be noted that for the same output energy of approximately 200 mJ (corresponding to 210Jcm-2 for the excimer and 1000Jcm-2 for the Nd:YAG) the excimers emitting in the UV ablates a factor of 7 more mass than the Nd:YAG emitting in the IR. Similar results were also obtained for targets made of molybdenum nickel and tungsten while the dependence on laser wavelength of the amount of material removed from a zinc target was less pronounced. In the second set of experiments the ablated mass versus melting temperature of different targets in air buffer gas at three different laser wavelengths was determined see Fig. 3. In the case of UV radiation a linear correlation exists between the ablated mass and the melting temperature of the sample material.In the case of IR radiation the differences in ablated mass are considerably larger and there exists no such simple 2 70 1 0 200 400 600 800 1000 1200 1400 Laser fluence/J cm-' Fig. 2 Ablation efficiency (mass ablated per laser fluence) on a copper target in air buffer gas as a function of laser energy for four different lasers. A ArF 193nm; B XeCl 308nm; C Nd YAG 355nm; D Nd:YAG 532 nm; and E Nd:YAG 1064 nmJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 19 Melting-point/K Fig. 3 Ablated mass versus fusion temperature of several targets (the element indicated was the major element in the target >99%) in air buffer gas at different laser wavelengths at a laser energy of 85 mJ per laser pulse (corresponding to a fluence of 90 J cm-' for the excimer laser (A XeCl 308nm) and 425 Jcm-' for the Nd:YAG lasers (B 532 nm; and C 1064 nm) relation between the ablated mass and the melting temperature of the sample material. The small number of measuring points in the case of visible laser radiation indicates a similar behav- iour as for IR radiation.This indicates a fundamental difference in the physics involved in the ablation process and might have important analytical consequences since it drastically reduces matrix effects in the case of UV laser sampling. The results obtained here for the IR laser agree well with results previously published by Kawaguchi et al.,' Ishida and Kubota' and Iidal' and indicate an almost exponential decrease in the ablated mass as a function of melting temperature in the case of an IR laser.In the third experiment three series of images of the emission from laser produced plasmas were obtained with a time resolution of 3 ns. The first series of four images shows plasmas produced by an IR laser on a copper target in argon buffer gas at a delay of approximately 30ns after the beginning of the laser pulse (6ns FWHM) (see Fig.4). The experimental conditions for the second series of images were identical to the first series except that air was used instead of argon as buffer gas; a representative plasma is shown in Fig. 5(a). The last series of images shows a plasma produced a UV laser on a copper target in argon buffer gas at a delay of approximately 30 ns after the beginning of the laser pulse [see Fig.5(b)]. The first observation is that the plasmas produced by an IR laser in argon are considerably more complex than those produced by a UV laser see Figs. 4 and 5(b) exhibiting several distinct plasmas. It is also clear from Fig. 4 that the reproducibility is poor for the plasmas produced by an IR laser in argon. The plasmas produced by an IR laser in air buffer gas also had a complex structure with two hot spots but the reproducibility was better than for the argon buffer gas. The plasmas produced by a UV laser in argon buffer gas Fig. 5(b) were confined close to the surface and consisted of one single plasma. The reproducibility of the plasma images with UV was considerably better than with IR produced plasmas.It should be noted that the experimental conditions used to obtain the images in Fig. 4 correspond well with the operating conditions used in commercial LA-ICP-MS apparatus. The lack of reproducibility of the plasma ignition observed in Fig. 4 probably explains the poor reproducibility observed in LA-ICP-MS measurements. The images suggest the following physical interpretation. When a high-power laser is focused on a metal target the intense radiation leads to rapid heating and evaporation of the solid. At the same time free electrons are created either by thermoelectric emission by multiphoton photoemission" or by multiphoton ionization of the metallic vapour or the ambient gas. These electrons absorb the incoming photons by inverse bremsstrahlung. This is necessarily a three-body process for reasons of conservation of both energy and momentum.The third body can be either an atom or an ion but the cross- sections are several orders of magnitudes greater for ions than for atoms. Therefore the heating of the electrons begins slowly before they acquire enough energy to ionize the gas collision- ally. This starts the cascade that leads to breakdown. In addition since the inverse bremsstrahlung cross-section of the ions relate to the wavelength as [1-exp(-hc/AkTjA3 the plasma will be much more absorbing in the IR than in the UV.12 Figs. 4 and 5(a) show that with IR radiation the absorption of the plasma is so strong that the energy is deposited at the leading edge of the plasma where it can lead to secondary or multiple breakdowns.This is not the case with UV laser produced plasmas where no breakdown of the buffer gas was observed [Fig. 5(b)] confirming results previously reported by Autin et al.13 The experimental observation that the highest acoustic levels were obtained when the laser beam was focused slightly in front of the sample (2 mm) with an IR laser whereas the beam was focused on the surface for a UV laser is another confirmation of a breakdown of the buffer gas in the case of IR laser produced plasmas. As a consequence of its higher absorption cross-section the IR plasma is hotter than the UV plasma14 and less energy in the laser beam interacts directly with the sample surface. In other words the plasma produced by the IR laser acts as a shield that only transfers a small part of the incoming laser energy towards the solid surface. These findings support the view that the UV and IR plasmas are essentially different as they interact in fundamentally different ways with the incoming laser radiation.The absence of multiple breakdowns in air buffer gas for IR produced plasmas could be explained by an easier ionization of argon gas than air and thus a higher inverse bremsstrahlung absorption coefficient due to the resulting ions. Although the ionization potential of argon is higher than that of nitrogen and oxygen metastable states in argon can serve as relay states and thereby facilitate the onset of a breakdown cascade which would explain the seemingly lower ionization potential of argon.15 Photographs taken with a scanning electron microscope of the crater forms obtained with UV and IR lasers respectively are presented in Fig.6. In the case of UV [see Fig. 6(c) and ( d ) ] there is a crater with well defined borders surrounded by a circular surface (with a diameter of approximately 600 pm) that is only slightly affected. With an IR laser [see Fig. 6(a) and (b) the crater formation is totally different without any clear limit between the actual crater and the surrounding affected zone. In addition the presence of a 'lip' of metal (indicated by an arrow) that had flowed out of the crater before it was solidified is visible in Fig. 6(b). The presence of the large affected region visible in Fig. 6(a) proves that it is the IR plasma that erodes the sample since the distances of heat diffusion in the targets used here (copper and aluminium16) are of the order of only 1 pm in 10 ns and 10 pm in 1 ms and thus too small to allow the heat deposited by the laser in the focal spot to diffuse over such a large surface.As a consequence of the shielding effect present in the case of an IR laser the relative importance of direct LA and plasma erosion are different for IR and UV lasers with UV radiation the direct laser interaction regime lasts the duration of the laser pulse (6 ns) whereas the importance of the plasma erosion is negligible [see Fig. 6(c)]. With IR radiation the direct laser interaction regime lasts only a fraction of the laser pulse (the time to reach breakdown probably less than 1 ns according to a model developed by Rosen et a1.17) and together with the fact that this plasma is considerably hotter the plasma erosion with an IR laser was found to be very important for the crater formation [see Fig.6(a) and (b)] and possibly also for the removal of material.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 ( b) Fig. 4 Images of the optical emission from a plasm,a produced by an Nd:YAG laser emitting at 1064 nm (IR) on a copper target in argon buffer gas at a delay of approximately 30 ns (after the beginning of the laser pulse). The laser beam is incident from the left and the target is situated vertically on the images at the right-hand side of the line shown above the plasmas (reflections on the metallic surface gives the impression that the plasma was situated inside the target).All four images (a)-@) are taken under identical experimental conditions Fig. 5 Images of the optical emission from a plasma produced by an Nd:YAG laser emitting at (a) 1064 nm (IR) ion a copper target in air buffer gas at a delay of approximately 30 ns (after the beginning of the laser pulse) and (b) 335 nm (UV) on a copper target in argon buffer gas at a delay of approximately 30 ns. The laser beam is incident from the left and the target is situated vertically on the image at the right-hand side of the line shown above the plasmas (reflections on the metallic surface gives the impression that the plasma was situated inside the target) In a publication by Hager," the relative elemental response for LA-ICP-MS was investigated using an Nd:YAG laser operating in the IR (Q-switched and free running).The results obtained confirmed that a thermal process is responsible for the evaporation in an IR laser. In a model developed by the author it was assumed that all the energy in the laser beam was deposited as heat in the target and that no screening effect was present. A formula was derived for the mass evaporated (for one specified matrix) that only included the heat of vaporization and the temperature of the solid which demon- strated good agreement between experiment and theory. Our interpretation based on the results presented by Hager," isJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 (a) (6) 21 - 100 pm 100 pm - 7 100 pm 100 pm Fig. 6 Scanning electron microscope images of the craters produced by 1000 laser shots from (a) and (b) an IR laser and (c) and ( d ) a UV laser in a copper target.The craters shown in Fig. 7(a) and (c) are given in greater detail in Fig. 7(b) and ( d ) respectively. The lip of molten metal is indicated by an arrow that the thermal model worked so well because it was the plasma (duration of some ps) rather than the laser (duration of 6 ns) that was responsible for the selective thermal evapor- ation of the elements. As has already been pointed out the curves in Fig. 2 show that another much more efficient ablation process is at work when using a UV laser. The crater images show that this process takes place with only minimal disturbance of nearby material. The process is thus non-selective and even though plasma erosion is also taking place the UV LA is globally less selective than IR LA because of the relative efficiencies of the two processes. It has previously been shown by Leis et d7 that excellent analytical signals can be obtained with LA optical emission spectrometry using an Nd:YAG laser at its fundamental IR frequency at a reduced pressure of the argon buffer gas of 140 hPa.The results obtained in the present study are not however do not contradict these results. According to the investigations of Rosen and Weyl,” the irradiation threshold for the break- down cascade is approximately the inverse of the pressure of the buffer gas times the square of the wavelength (pA2)-’ Hence when Leis et ~ 1 . ~ used 1064 nm instead of 355 nm they off-set the variation in breakdown thresholds due to the wavelength change by decreasing the pressure and could thus perform the ablation without screening by the plasma or formation of multiple plasmas.Conclusion The results presented in this paper demonstrate large differ- ences between UV and IR lasers for laser solid sampling. The mass ablated by a UV laser is considerably larger than for an IR laser under operating conditions similar to those employed for LA-ICP-MS. Considering that the detection limits are already very good sub-ppm and that the amount of sample material that can be accepted by an ICP mass spectrometer is limited this advantage of UV laser sampling might not be capable of being exploited to its full extent in LA-ICP-MS. An excimer laser could because of the large masses ablated (Fig. 2) lead to blocking of the sampler; for the purposes of ICP-MS a frequency-tripled Nd:YAG laser would be quite sufficient.However if the detection of the ablated material is performed by ICP-AES the larger mass ablated by a UV excimer laser can be exploited to its full extent possibly leading to a similar analytical performance as LA-ICP-MS.20 Time resolved images of the optical emission from the early evolution of laser produced plasmas revealed a complex struc- ture and poor reproducibility in the case of an IR laser while a reproducible plasma with a simple geometrical structure was obtained with a UV laser. It is probable although no evidence is given in this paper that the reproducibility and complexity of the plasma emission is related to the reproducibility in22 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL.9 LA-ICP-MS measurements in which case considerably better reproducibility is to be expected if a UV laser is used instead of an IR laser for the laser sampling. The lateral spatial resolution of the laser sampling for metallic targets is given approximately by the laser focal spot size in the case of a UV laser while it is determined by the size of the plasma for an IR laser. Hence considerably better spatial resolution is obtained with UV laser sampling. Direct LA taking place during a few ns is the major process responsible for the removal of material in the case of a UV laser. This is in contrast to the case with an IR laser where shielding of the laser radiation limits the direct LA and increases the temperature of the plasma leading to an increased selective removal of material by the plasma.As a consequence the risk of selective vaporization is minimized if UV laser sampling is used for LA-ICP-MS. Measurements of the ablated mass versus fusion temperature strongly suggest a considerably simpler quantification of the signal with UV laser sampling. Hence for the operating conditions pertaining to LA-ICP-MS the results presented in this paper strongly indicate that UV laser sampling is far superior to IR laser sampling in every analytical aspect reproducibility matrix effects spatial resolution quantification and sensitivity. To conclude it is the authors' firm belief that the use of frequency- tripled ND:YAG laser sampling in LA-ICP-MS would lead to a new breakthrough of this technique with considerably better analytical characteristics.The authors express their appreciation to B. Dubreuil and V. Martin-Daguet for helpful discussions and L. Battery for his assistance in taking the SEM micrographs. S.S. acknowl- edges support from the Swedish-French research exchange foundation and the Swedish Institute. This work was in part funded by the French Research Group on Analytical Laser Ablation (GRAAL) with the following participants C.E.A. CNRS DILOR Jobin Yvon Pechiney Renault Sollac Saint- Gobain and the French Ministkre de la Recherche. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 References Gray A. L. Analyst 1985 110 551. Arrowsmith J. W. Anal. Chem. 1987 59 1437. Moenke-Blankenburg L. Spectrochim. Acta Rev. 1993 1 1. ' Chen G. and Yeung E. S. Anal. Chew. 1988 60 2258. Jones R. D. and Scott T. R. Laser Focus World 1993 123 185. AndrC N. Briand A. Lacour J.-L. Mauchien P. Semerok A. and Sjostrom S. in preparation. Leis F. Sdorra W. KO J. B. and Niemax K. Mikrochim. Acta 1989 11 185. Kawaguchi H. Xu J. Tanaka T. and Mizuike A. Bunzeki Kagaku 1982 31 El85 Ishida R. and Kubota M. J. Spectrosc. SOC. Jap. 1972 21 16. Iida Y. Spectrochim. Acta. Part B 1990 45 1353. Petite G. Agostini P. Guizard S. Martin P. and Trainham R. Laser Ablation of Electronic Materials ed. Fogarassy E. and Lazare S. Elsevier 1992 p. 12. Weyland G. M. and Rosen D. Phys. Rev. A 1985,31 2300. Autin M. Briand A. Mauchien P. and Mermet J. M. Spectrochim. Acta Part B 48 851. Girault C. Ph.D. Thesis UniversitC de Limoges France 1990. Zel'dovich Ya. and Raizer Yu. Sou. Phys. JETP (Engl. Transl.) 1965 20 772. von Allmen M. Laser Beam Interaction With Materials Springer- Verlag Berlin 1987. Rosen D. I. Hastings D. E. and Weyl G. J. Appl. Phys. 1982 53 5882. Hager J. W. Anal. Chem. 1989 61 1243. Rosen D. I. and Weyl G. J. Phys. D 1987 20 1264. Chartier F. Ph.D. Thesis 1'Universite Claude Bernard Lyon 1991. Paper 3/03535B Received June 21 1993 Accepted September 17 1993

ISSN:0267-9477    

DOI:10.1039/JA9940900017

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

1995 European Winter Conference on Plasma Spectrochemistry 8-13 January 1995 CAMBRIDGE UK Short Courses A series of short courses of one half day duration will take place on Sunday 8th January. Notes and tuition material will be distributed with each course. Courses 1 and 2 Short Courses on ICP-MS Professor R.S. Houk Ames Laboratory Iowa State University USA Course 1 (AM) Instrumentation and Theory The course will cover fundamental aspects of ICP-MS including:- a) Molecular beam sampling b) Quadrupole and high resolution c) Vacuum technology d) Ion sources e) Detection systems and data hand1 ing f) Sample introduction technologies analys ers Course 2 (PM) Advanced Topics The course will cover more advanced topics on ICP-MS particularly relevant to problem solving. Each topic will be illustrated with relevant applications examples.a) Interferences (spectroscopic and non-spectroscopic and methods of alleviation b) Isotopic analysis c) Chromatographic methods d) Overview of commercial instrumentation Course 3 (PM) Sample Preparation for ICPs Dr S.J. Haswell Hull University UK The course will focus on important aspects of sampling and sample preparation with particular emphasis on ICP measurements. a) Batch methods f o r wet oxidation b) Recent trends in microwave preparation for ICP-MS atomic spectrometry general analytical techniques c) On-line sample preparation d) Extraction methods e) On-line chemical processing f) Miniaturization Course 4 (PM) Speciation Professor O.X. Donard University of Bordeaux France The course will focus on practical aspects of speciation analysis with particular emphasis on ICP and other plasma sampling systems.Sample collection and handling preservation and preparation prior to injection into hyphenated systems using atomic spectrometry and ICP-AES or ICP-MS as detectors will be illustrated with applications from current topical fields . a) Sampling and sample pretreatment b) Separative techniques Differential chemistry Gas liquid ion and SCF c ) Interfacing chromatography techniques to ICPs and other plasma sources and detectors chromatographies Course 5 (AM) Quality Systems in the Laboratory Professor L. Ebdon Dr E.H. Evans University of Plymouth UK The course will discuss how high quality analytical data can be produced in the laboratory that are accurate reliable and adequate f o r the intended purpose.a) Quality assurance principles b) Sampling and sample preparation c) Personnel aspects d) Statistics for quality control e Use of reference materials and f) Equipment and records maintenance g) Audits and accreditation. traceability Course 6 (AM) Sample Presentation for ICPS Dr C McLeod Sheffield Hallam University UK The course is intended as a problem solving workshop and will attempt to rationalise the choice of sampling system for ICP spectrometries by use of practical examples. a) Nebulisation techniques Traditional and high efficiency The role of desolvation Hydride Other vapour techniques e . g . b) Vapour generation Hg oso c) Microsampling systems d) Flow injection e) Laser ablation1995 European Winter Conference on Plasma Spectrochemistry 8-13 January 1995 CAMBRIDGE UK Short Courses A series of short courses of one half day duration will take place on Sunday 8th January. Notes and tuition material will be distributed with each course.Courses 1 and 2 Short Courses on ICP-MS Professor R.S. Houk Ames Laboratory Iowa State University USA Course 1 (AM) Instrumentation and Theory The course will cover fundamental aspects of ICP-MS including:- a) Molecular beam sampling b) Quadrupole and high resolution c) Vacuum technology d) Ion sources e) Detection systems and data hand1 ing f) Sample introduction technologies analys ers Course 2 (PM) Advanced Topics The course will cover more advanced topics on ICP-MS particularly relevant to problem solving. Each topic will be illustrated with relevant applications examples.a) Interferences (spectroscopic and non-spectroscopic and methods of alleviation b) Isotopic analysis c) Chromatographic methods d) Overview of commercial instrumentation Course 3 (PM) Sample Preparation for ICPs Dr S.J. Haswell Hull University UK The course will focus on important aspects of sampling and sample preparation with particular emphasis on ICP measurements. a) Batch methods f o r wet oxidation b) Recent trends in microwave preparation for ICP-MS atomic spectrometry general analytical techniques c) On-line sample preparation d) Extraction methods e) On-line chemical processing f) Miniaturization Course 4 (PM) Speciation Professor O.X. Donard University of Bordeaux France The course will focus on practical aspects of speciation analysis with particular emphasis on ICP and other plasma sampling systems.Sample collection and handling preservation and preparation prior to injection into hyphenated systems using atomic spectrometry and ICP-AES or ICP-MS as detectors will be illustrated with applications from current topical fields . a) Sampling and sample pretreatment b) Separative techniques Differential chemistry Gas liquid ion and SCF c ) Interfacing chromatography techniques to ICPs and other plasma sources and detectors chromatographies Course 5 (AM) Quality Systems in the Laboratory Professor L. Ebdon Dr E.H. Evans University of Plymouth UK The course will discuss how high quality analytical data can be produced in the laboratory that are accurate reliable and adequate f o r the intended purpose. a) Quality assurance principles b) Sampling and sample preparation c) Personnel aspects d) Statistics for quality control e Use of reference materials and f) Equipment and records maintenance g) Audits and accreditation. traceability Course 6 (AM) Sample Presentation for ICPS Dr C McLeod Sheffield Hallam University UK The course is intended as a problem solving workshop and will attempt to rationalise the choice of sampling system for ICP spectrometries by use of practical examples. a) Nebulisation techniques Traditional and high efficiency The role of desolvation Hydride Other vapour techniques e . g . b) Vapour generation Hg oso c) Microsampling systems d) Flow injection e) Laser ablation

ISSN:0267-9477    

DOI:10.1039/JA99409BX019

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 23 Use of Inductively Coupled Plasma Mass Spectrometry for the Determination of Ultra-trace Elements in Human Serum Hans Vanhoe and Richard Dams Laboratory of Analytical Chemistry University of Ghent Institute of Nuclear Sciences Proeftuinstraat 86 6-9000 Ghent Belgium Jacques Versieck Department of Internal Medicine Division of Gastroenterology University Hospital De Pintelaan 185 6-9000 Ghent Belgium A method for the determination of 11 ultra-trace elements (Li B Mo Cd Sn Sb Cs Ba Hg Pb and Bi) in human serum by inductively coupled plasma mass spectrometry is described. Sample preparation was kept to a minimum serum samples were diluted 5-fold with 0.14 mol I-’ HNO and suitable internal standards (Be In and TI) were added to correct for matrix effects and for ion signal instability. Special attention was given to optimization of the electrostatic lens settings and the nebulizer gas flow rate.Detection limits between 0.007 ng ml-‘ (for Bi) and 0.5 ng ml-’ (for B) could be obtained taking into account a 5-fold dilution of the serum sample. Memory effects which can be experienced with the conventional methodology for sample introduction leading to positive errors were reduced to a negligible level by the use of a short (2 min) clean-out procedure. With the exception of B (1-2 ng ml-’) and Pb (0.08-0.15 ng mi-’) blank levels were shown to be below 0.1 ng ml-‘. Results are given for a ‘second-generation’ biological reference material Freeze-Dried Human Serum (University of Ghent) and for Human Serum SRM 909 from the National Institute of Standards and Technology (for Li Cd and Pb).Finally serum samples from healthy individuals were analysed in order to determine typical element concentrations for normal human serum. Keywords Inductively coupled plasma mass spectrometry; ultra-trace element determination; human serum Because of its extreme importance for the human organism and easy accessibility human blood plasma or serum has been selected by many clinical and analytical scientists for the determination of trace and ultra-trace elements. The concen- trations of the trace elements to be determined vary from 10 pg ml-’ to less than 0.1 ng ml-’. Some of these are essential like Co and Mo or toxic like Hg and Pb and are therefore an interesting group for intensive investigation.In order to determine elements at the ultra-trace level (less than 10 ng ml-’) sensitive analytical methods are required. Neutron activation analysis (NAA) electrothermal atomic absorption spectrometry (ETAAS) inductively coupled plasma atomic emission (ICP-AES) and mass spectrometry (ICP-MS) and proton induced X-ray emission spectrometry (PIXE) have often been used for these purposes. So far radiochemical and instrumental neutron activation analysis (RNAA and INAA)’-’ and ETAAS+” are almost the only techniques that have been employed for the determination of ultra-trace elements in human serum.12 Since ETAAS is hampered by the occurrence of matrix effects and has a single-element character and because for NAA long waiting times or elaborate radiochemical separations are often involved the development of an alterna- tive analytical technique was desirable.Therefore the use of ICP-MS which combines the exceptional characteristics of the ICP for the atomization and ionization of the injected sample with the sensitivity and selectivity of MS was evaluated. Since its commercial introduction in 1983 ICP-MS has been exten- sively used in the determination of elements at the trace and ultra-trace level in biological material~.’~-~ Recently a review of the capabilities of ICP-MS for the determination of trace elements in body fluids and tissues was published.24 Besides the direct analysis of biological certified reference materials by laser ablation ICP-MS2’ and the use of flow injection (FI) for the analysis of undiluted urine,” all appli- cations devoted to biological fluids involve more or less extensive sample preparation prior to analysis.Special care has to be taken during sample preparation to minimize con- tamination of the samples and losses of analytes by volatiliz- ation adsorption or precipitation. A first sample preparation method is based on the destruction of the organic material present in the sample. Most often digestion with one or more acids e.g. HNO HClO and/or H2S04 is used. Disadvantages of this technique are the possible introduction of significant blanks from the acids and the loss of volatile elements such as Hg. The latter problem can be avoided by the use of high-pressure bombs or microwave oven digestions.This procedure has been applied for the analysis of urine,” human blood plasma2c28 and human blood by ICP-MS.28-31 A suitable alternative is ashing of the biological material. Lyon et a!.’’ and Wang et ~ 1 . ~ ~ applied this method to urine whereas Serfass et ashed blood plasma at 480°C before the measurement of Zn-isotope ratios. Finally Smith et a!.34 reported the determination of B in blood plasma after a sodium carbonate fusion and separation of B from the matrix compo- nents using a selective ion-exchange resin. A second method that limits the sample preparation is dilution of the biological fluid with a suitable diluent. Although this method necessarily introduces a deterioration of the detection limits accurate determination of several elements is still possible.Mulligan et aZ.35 showed the capability of ICP-MS for the analysis of urine after 10-fold dilution with 0.14 mol I-’ HNO (for the determination of Cd Sb and Hg). Ba~mann,~ and Vanhoe et a1.37 described the rapid and accurate determination of I in milk after dilution with 1% v/v ammonium solution whereas Dean et demonstrated the accurate determination of Pb isotope ratios in milk after an approximately 40-fold dilution with 0.1 YO Triton X-100 solution. Another biological fluid that has already been analysed after simple dilution is blood. A roughly 25-fold dilution with a 5% Triton X-100 solution appeared to be sufficient to determine accurately both the total Pb content and the Pb isotope In order to minimize contamination and losses of analyte in this laboratory an attempt was always made to limit the sample preparation to a 5-fold dilution with 0.14 moll-’ HNO,.From the composition of human serum it is obvious that apart from the water and the protein content there is a considerable salt content with Na K and Ca as easily ionizable elements and S and C1 as major interfering elements. The salt24 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 content is equivalent to 9 mg ml-' of NaCl or 0.9%. This can lead to signal suppression of up to more than 3O-40Yi4' In order to correct for these matrix effects and for signal instabil- ity several internal standards (Be Co In and T1) were added to the sample solution. In addition some proteins may deposit in the central part of the torch and salts may clog the sampling cone or the nebulizer.Lyon et a/.'' analysed synthetic protein solutions after a 10-fold dilution and achieved reasonable results for Al Cr Mn Fe Ni Cu Zn Mo and Ba. Besides for Mo (at a concentration of about 7 ng ml-') the concen- tration of the elements mentioned ranged from 80 ng ml-' (for Ba) to 7 pg ml-' (for Fe). Park et determined Cr Cu and Pb in National Institute for Standards and Technology (NIST) Standard Reference Material (SRM) 909 Human Serum after a 10-fold dilution. It should be realized that the concentration of elements in the serum samples mentioned above are signifi- cantly higher (up to a factor of 1000) than expected in normal human serum. In order to evaluate the potential of ICP-MS for the determination of ultra-trace elements in human serum a serum reference material with trace element levels comparable to those found in normal human serum was employed namely a 'second-generation' biological reference material Freeze- Dried Human Serum identical to the material used for the determination of Fe Co Cu Zn Rb," Sr,43 Br44 and I.37 This reference serum was prepared by Versieck et a1.45 under rigorously controlled conditions in order to avoid the addition of extraneous species.Experimental Instrumentation The ICP mass spectrometer used was a VG PlasmaQuad (VG Elemental Winsford Cheshire UK) equipped with a Gilson-2 peristaltic pump a Meinhard concentric glass nebulizer (type TR-30-A3) a Scott-type double pass spray chamber with surrounding liquid jacket made of borosilicate glass and a Fassel-type torch.Details of the operating conditions are summarized in Table 1. Reagents and Standards High-purity water was obtained with a Millipore Milli-Q water purification system (resistivity of 18 MR cm). Concentrated nitric acid (14 moll-') was purified by sub-boiling distillation in a quartz still using analytical-reagent grade nitric acid (Pleuger) as feedstock. External calibration using single-element standard solutions with a concentration of 0.5 1 5 and 10ngml-' to produce Table 1 ICP-MS operating conditions ~~~~ ~~ Stage Parameter Plasma R.f. power Forward Reflected Gas flows Plasma Intermediate Nebulizer Peristaltic pump Nebulizer Spray chamber Ion sampling Sampling cone Skimmer cone Sampling depth Vacuum Expansion stage Intermediate stage Analyser stage 1.35 kW <low Conditions 13 1 min-' 1 1 min-l Variable Minipuls 2 (Gilson) pumped at 0.9 ml min-' Meinhard Tr-30-A3 concentric glass nebulizer Double-pass Scott type water-cooled (10 "C) Nickel 1.0 mm orifice Nickel 0.75 mm orifice 10 mm (from load coil) 2.4 mbar 1.0 x mbar 4.0 x lop6 mbar single-element calibration curves was employed to calculate the concentration of the analyte elements.Special attention was given to the purity stability and accuracy of the standards used. Table 2 gives for each element the product used for the preparation of the standard solutions. The single-element standard solutions with concentrations between 0.5 and 10 ng ml-' were freshly prepared before each analysis sequence. For the internal standards use was made of commerically available AAS standard solutions Be and In (Janssen Chimica) and T1 (Alfa Products).Sample Preparation Blood samples from healthy subjects working in this labora- tory were collected and processed according to the sampling protocol developed at the institute and described in detail by Versieck and Cornelis.12 Briefly in order to avoid significant contamination at the sampling stage blood was taken with a polypropylene intravenous catheter mounted on a metallic needle [Intranule 110 16 (Vygon)] and collected in high-purity quartz tubes with stoppers made of poly(tetrafluoroethy1ene) (PTFE). No anticoagulant was added. After collection samples were immediately placed in a thoroughly cleaned plastic box and transported into a clean laboratory where all further sample handling was performed.After clotting serum was separated by centrifugation (3500 rev min-' for about 30 min) and decanted into polyethylene screw-cap containers. Afterwards the serum samples were stored at -25 "C prior to analysis. After defrosting and homogenization with a quartz stirring- spoon (the whole process took about 2 h) 5 ml of liquid serum taken with a polyethylene pipette (Kartell) were transferred into a 25 ml polyethylene calibrated flask. After addition of 2.5 ml of a multi-element solution (100 ng ml-' of Be In and T1 used as internal standards) the solution was adjusted to volume with 0.14 moll-' HNO,. A blank solution was pre- pared in the same way as the serum solutions but without the addition of sample. For lyophilized serum the form in which the 'second-generation' biological reference material Freeze- Dried Human Serum is available first the sample was reconsti- tuted with Millipore Milli-Q water in a PTFE beaker ( 6 ml of water for 500 mg of sample) before being quantitatively trans- Table 2 Standards used for the analysis of human serum Element Standard Li B Mo Li,C03 (powder) IRM-016 (CBNM Geel) solvent H,O; diluent 0.14 moll-' HNO H,BO (powder) IRM-011 (CBNM Geel) solvent and diluent 0.14 moll-' HNO AAS standard solution (Johnson Matthey) solvent 5% HCl and traces of HF diluent 0.1 moll-' HCl solvent 14 mol I-' HNO,; diluent 0.14 mol I-' HNO solvent 1:l HNO (14 moll-') HCl(l0 moll-'); diluent 1 moll-' HC1 (first step) 0.1 moll-' HCl diluent 0.1 mol I-' HC1 diluent 0.14 moll-' HNO solvent and diluent 0.14 mol 1-' HNO solvent 0.7 moll-' HNO and 0.025% K,Cr,O,; diluent 0.14 moll - HNO solvent 0.14 moll-' HNO solvent 14 moll-' HNO,; diluent 0.14 moll-' HNO Cd Sn Cd metal (Goodfellow Metals 99.95%) Sn wire (Goodfellow Metals 99.99%) Sb Cs Ba Hg Hg metal AAS standard solution (Alfa Products) AAS standard solution (Alfa Products) Ba(NO,) (powder) (Merck analytical reagent grade) Pb Bi Pb( NO,)z (UCB analytical-reagent grade) Bi metal (Vieille Montagne 99.999%)JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL.9 25 fered into a calibrated flask with the diluent (0.14moll-1 HNO,). All manipulations were performed on a clean-bench. Human Serum SRM 909 was reconstituted with diluent water as described in the NIST certificate. A dilution factor of 5 (for Cd and Pb) or 50 (for Li) was used by diluting respectively 5 ml or 500 p1 of the reconstituted solution to 25 ml with 0.14 moll-' HN03.Optimization of the Instrumental Parameters In order to obtain maximum signal intensity necessary for the determination of elements at ultra-trace levels in human serum several parameters have to be optimized. Both gas flow rates and electrostatic lens settings were studied in more detail. Nebulizer gasflow rate It is generally accepted that the signal response is strongly dependent on the nebulizer gas flow rate. At one particular radiofrequency (r.f.) power each M+ signal shows a maximum intensity at a certain nebulizer gas flow rate. In addition as described by Vanhaecke et the optimum nebulizer gas flow rate is mass dependent with the heavier elements having a lower optimum nebulizer flow rate at a particular r.f. power.Therefore in order to determine elements at the ultra-trace level it is necessary to use different nebulizer gas flow rates depending on the analyte elements as shown in Fig. 1. For the analysis of human serum three nebulizer gas flow rates were employed 0.7801min-1 for the light elements (Li and B) 0.725 1 min-l for the mid-mass elements (Mo Cd Sn Sb Cs and Ba) and 0.700 1 min-' for the heavy elements (Hg Pb and Bi). It is worth mentioning that the intermediate gas flow rate shows a less pronounced effect and was set at 1 1 min-' (Table 1). Lens voltages In addition to the nebulizer gas flow rate the lens voltages can significantly influence sensitivity.In the optimization study a different behaviour was noticed for various nuclides as illustrated in Fig. 2 which shows the relation between the normalized ion signals for 'Be "CO "'In and 238U and the voltage on lens 2 which is positioned behind the photon stop. Firstly all lenses were adjusted to obtain a maximum signal intensity for 1151n. Afterwards all voltages were kept constant except the voltage on lens 2. From Fig. 2 it is clear that the ion signals for the four nuclides do not behave in the same way. These observations are in agreement with the conclusions of Schmit and Chtaib,47 Vaughan and H~rlick,~' and Tanner49 who reported that there is a mass dependency of the trajectories that the ions describe through the electrostatic lens system.Therefore before each analytical sequence the lens settings 700 I 600 = 500 600 700 800 900 Nebulizer gas flow rate/ml min-' Fig. 1 A 9Be; B "'In; and C '05Tl Influence of the nebulizer gas flow rate on the ion signal for 0' I I 1 . 1 1 I I 1 I -160 -140 -120 -100 -80 -60 -40 -20 0 20 Lens 2 voltageN Fig.2 Influence of the lens 2 voltage on the ion signal for A 9Be; B 59C0; C Ir51n; and D 238U were optimized in order to obtain a maximum ion signal intensity for the internal standard used. Choice of Internal Standard In previous work18,43,44 it was reported that the signal intensity is influenced by the serum matrix. In addition it was noticed that the heavy elements are suppressed to a larger extent than the lighter elements for 4 mg ml-' of NaCl the signal suppres- sion increases from 33% for 7Li to 56% for 238U.Therefore in order to obtain accurate results a method must be developed to correct for these matrix effects which are mainly caused by easily ionizable elements such as Na K and Ca. The method applied was based on the use of internal standardization. Because the signal suppression was established to be mass dependent the choice of suitable internal standards was exam- ined. Serum solutions which were diluted 5-fold were spiked with a multi-element standard solution (each element at a concentration level of 100 ng ml-') and compared with a blank solution containing the multi-element solution in 0.14 moll-' HNO,. The results are summarized in Table 3 the experimental recoveries range from 98.7 to 102.6% using a suitable internal standard.It can be concluded that a suitable internal standard with a mass close to that of the analyte element accurately corrects for matrix effects in the case of human serum. For that reason three internal standards (at a concentration level of 10ngml-') were employed beryllium (9Be) for the light elements indium ("'In) for the mid-mass elements and thallium ('''Tl) for the heavy elements. Moreover the internal standard corrects also for instability of the ion signal so that a relative standard deviation (RSD) on the results of 4% or better can be expected in cases with sufficient counting statistics. Method of Analysis and Calculations Several experiments showed that when the measuring time is increased an improvement in the detection limit proportional to the square root of the increase of the measuring time can Table 3 Results of recovery experiments Nuclide 7Li 1°B 9 8 ~ ~ '"Cd lz0Sn lZ1Sb 133cs 138Ba 202Hg zosPb 209~i Internal standard 9Be 9Be lIsIn '"In 1 1 5 1 ~ 1 1 5 1 ~ "51n 1 1 5 1 ~ 2 0 5 ~ 1 2 0 5 ~ 1 20sT1 Recovery( YO) 102.6 -t 2.7 99.6 & 2.5 101.0+ 1.4 99.6 k 2.5 98.7 k 2.6 101.4+ 1.3 99.4 & 0.8 100.8 & 1.9 102.0k2.1 100.2k0.9 99.2 f.2.026 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 Table 4 Scanning conditions for the ultra-trace element analysis of human serum; internal standards used are given in parentheses Elements Mass range/u Dwell time,@ Channels Sweeps Li B (Be) 4-1 1 320 512 400 Cd Sn Sb (In) 109-124 320 512 400 Hg Pb Bi (Tl) 199-21 0 320 512 400 Mo (In) 96-1 17 320 512 400 Cs Ba (In) 113-140 320 1024 200 be expected. For this reason to perform an ultra-trace element analysis of human serum it is necessary to limit the number of analytes determined simultaneously to a few elements with comparable masses.Therefore the mass range was divided into several parts consisting of 20-30 u (Table 4). In order to obtain a correct integration of the peaks each peak must consist of at least 20 channels. Hence 512 or 1024 channels with a dwell time of 3 2 0 p were used so that short-term fluctuations on the ion signal intensity were largely eliminated. Finally the mass range was scanned 200 times (for 1024 channels) or 400 times (for 512 channels) so that one measure- ment lasted about 1 min. Five replicates were made on each solution.Memory effects which are encountered for elements such as Li,50 B,51 Mo," Sn Hg and Bi,52 were reduced to a negligible level by the use of the following analysis sequence first a blank for the samples was measured then several serum samples next a blank for the standard and only at the end of the sequence several single-element standard solutions with con- centrations up to a maximum of 10ngml-'. Moreover the sample introduction system was rinsed for at least 2 min with 0.14 mol 1-' HNO after the measurement of each solution and the blank level was controlled with a rate meter. Finally before each analysis sequence the sampling and skimmer cones were cleaned and all parts of the sample introduction system were leached with concentrated nitric acid. For each solution (blank sample standard) the signal (peak area integrated over 0.8 u around the peak maximum) of each nuclide was normalized to the signal of the internal standard.The mean and standard deviation of the five resulting nor- malized signals of each solution were calculated. The average normalized signal of the blank was subtracted from that of the serum solutions. External calibration (calibration curve) was employed to calculate the corresponding concentrations. Results and Discussion Blank Levels and Detection Limits In order to determine very low concentrations it is necessary that the blank values are as low as possible. The elevation of the blank signal can have several origins. One of these is contamination of the reagents used for sample preparation. For that reason use was made of de-ionized water which was purified by a Millipore Milli-Q system so that a resistivity of 18 MR cm was obtained.In addition nitric acid was purified by sub-boiling distillation to remove impurities present in the feedstock. Table 5 gives the concentration levels for the analyte elements found in a blank solution consisting of 0.14 moll-' HNO,. Except for B and Pb all concentrations are below 0.1 ng ml-'. Experiments showed that most of the boron is present in the Millipore Milli-Q water whereas the sub-boiled nitric acid contains traces of Sn Ba and Pb. The blank signal for Hg originates from impurities present in the Ar gas. For the other elements the blank signals observed are due to the continuous background present over the whole mass range.Since the background signal is stable over several hours (Fig. 3) it is possible to correct for the contribution of the background which is not negligible for ultra-trace element determinations by measuring a blank solution. Table 5 gives detection limits (34 a blank solution was measured ten times) obtained with the scanning conditions Table 5 Blank levels and detection limits Element (nuclide) Li ('Li) B ('OB) Mo ('*Mo) Cd (l14Cd) Sn ('"Sn) Sb (121Sb) c s (l33Cs) Ba ('38Ba) Hg (202Hg) Pb ('08Pb) Bi ("'Bi) Blank value/ ng ml-' 0.02-0.04 1-2 0.01-0.03 0.01-0.02 0.02-0.06 0.01-0.02 0.005-0.015 0.02-0.05 0.04-0.08 0.08-0.15 0.001-0.003 Concentration in Detection limit*/ human serum/ ng i d - ' ng ml-l 0.05 1 0.5 5-50 0.04 0.3-1.2 0.02 0.1-0.2 0.05 0.03 < 0.5 0.03 1 0.2 0.1-4.8 0.1 0.02-4 0.007 <0.1 0.40-0.64 0.04 ?( < 10) * Taking into account a 5-fold dilution of the serum sample.100 UJ v) 3 0 L m C v) U C 3 P Y m 4-l (J 10 .- 2 m r T I IJOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 27 already summarized in Table4 and compares these with the element concentration expected in normal human serum. The detection limits vary from 0.007 ngml-' (for '09Bi) to 0.5 ng ml-' (for 'OB) taking into account a 5-fold dilution of the serum sample. For Li B Mo Sn Cs and Ba the detection limit is at least a factor of 10 lower than the concentration in human serum whereas for Cd Sb Hg Pb and Bi the serum concentration is in some cases lower than the detection limit. In order to check the accuracy and precision of the method developed two serum reference materials were analysed namely a 'second-generation' biological reference material Freeze-Dried Human Serum (University of Ghent) and Human Serum SRM 909 (from NIST).Results for the 'second- generation' biological reference material Freeze-Dried Human Serum are given in Table 6 whereas Table 7 gives results for Human Serum SRM 909 (for Li Cd and Pb). As an application serum samples from healthy individuals were analysed. The concentration levels obtained are given in Table 8. The results for each element are discussed below in more detail. Lithium Because of the lower detection limit and the smaller influence of variations of the isotopic composition of Li determinations were made using the most abundant isotope 'Li (92.5%). They resulted in a mean Li concentration of 15.04 ng g-' (corre- sponding to 1.37 ng ml-' for serum obtained after reconsti- tution of the lyophilized form). The RSD on the measurements varies from 2.3 to 4.2% whereas the contribution of the blank signal to the total signal in human serum amounts to a maximum value of 13%.The result obtained is in good agreement with that of Ab~u-Shakra~~ (using ICP-MS). The value using ETAAS54 (no background correction) is somewhat higher. The results for Human Serum SRM 909 (Table 7) are in good agreement with the certified value. It should be noted that the concentration of Li in this reference serum is about a factor of 8000 higher than that of the 'second-generation' biological reference material Freeze-Dried Human Serum.For normal human serum a range between 0.25 and 0.87 ng ml-' with a mean Li concentration of 0.60 ng ml-' was found. Literature values mainly obtained by ETAAS range from 0.2 to 44 ng ml-'. Since the concentrations of Li in human serum are low and higher Li values were only obtained with less sensitive techniques such as flame AAS probably the normal concentration of Li is less than 5 ng ml-' (a mean of 1 ngml-') which is in agreement with the result obtained here. Determinations of Li in human serum and other biological materials have been discussed in more detail in a previous p ~ b l i c a t i o n . ~ ~ Boron In order to avoid the overlap from the intense ''C' peak with the "B' peak,51 'OB (20%) was used for the determination of B.A mean B concentration of 227 ng g-' was obtained (corresponding to 20.6 ng ml-' for liquid serum). This result is in excellent agreement with that of Ab~u-Shakra~~ (using ICP-MS). Although the contribution of the blank signal to the total signal in human serum is relatively high (between 20 Table 6 Results (ng g- ' dry mass*) for the 'second-generation' biological reference material Freeze-dried Human Serum. Values can be recalculated into ng ml-' of original liquid serum by dividing them by 11 i.e. loo/( 1.025 x 8.87) (1.025 being the density of the fresh serum and 8.87 the mean percent residue after lyophilization). Values in parentheses are the standard deviation n = s 'Li ICP-MS Individual results 15.32( 0.64) 15.03 (0.34) 15.09(0.39) 14.73 (0.59) 15.04 f0.39 19.25 f0.55 ( ETAAS)54 14.8 f 2.8 ( ICP-MS)53 Mean f 95% confidence limits Certified or literature values ICP-MS individual results Mean f 95% confidence limits Certified or literature values ICP-MS individual results '14Cd 2.05( 0.47) 2.93( 0.24) 1.65(0.38) 2.22( 0.24) 2.21 f 0.85 138Ba 9.77( 0.45) 13.3 ( 1 .O) 12.06( 0.5 1 ) 9.12(0.30) Mean k 95% confidence limits Certified or literature values 11.1 f3.1 'OB 217.7( 6.8) 241 (10) 21 8.5 ( 3.6) 230.0( 7.7) 227 f 18 222 6 ( ICP-MS)53 '18Sn 9.97(0.51) 9.88( 0.93) 11.3( 1.1) 8.84( 0.30) 10.81 (0.67) 8.93(0.47) 9.71(0.46) 9.92 10.83 10 f 2.6 (NAA)' 7.6 & 1.4 7.96 f 0.97; 8.38 f0.48 (NAA)57 '"Hg 6.77( 0.40) 6.87(0.54) 6.64( 0.50) 5.66(0.75) ( ICP-MS)54 6.49 & 0.89 6.6 f0.445 9 8 ~ ~ 6.89( 0.69) 8.06( 0.73) 7.63(0.81) 7.46( 0.68) 7.51 f0.77 7.5 k 0.845 "*Sn 9.65(0.46) 10.38( 0.61) 10.90( 0.90) 8.69(0.91) 10.83 (0.77) 8.67(0.45) 9.30( 0.44) 9.77 f 0.88 'O'Hg 6.43( 0.80) 5.67(0.41) 5.44( 0.7 1 ) 7.7( 1.2) 6.3 -t 1.6 "'Cd "'Cd "'Cd 2.67( 0.43) 1.96(0.63) [ 3.24(0.88)]* 1.73(0.72) 2.56( 0.32) 1.92( 0.5 1) 1.64( 0.6 1 ) 2.55( 0.39) 1.57( 0.53) 2.45(0.95) 1.83( 0.74) 1.87( 0.68) 2.12 -t 0.8 1 2.23 f 0.61 1.79 f 0.47 2.0( 1.7-2.5)45 '"Sb 123Sb 133cs 0.89( 0.37) 1.07 (0.46) 10.88( 0.83) 0.61 (0.40) 0.83 (0.33) 10.23 (0.3 1) 1.04(0.26) 0.70( 0.36) 9.76( 0.44) 0.93( 0.25) 0.44( 0.30) 9.9 1 (0.27) 0.87 & 0.29 0.76 f 0.42 10.20 f 0.79 0.25f0.15 10.0 f 2.345 (NAA)' ZOgBi '08Pb 42.62(0.66) 0.708( 0.096) 40.9( 1.2) 0.61 3( 0.064) 48.1(2.5) 0.773( 0.048) 44.6( 2.1) 0.683 (0.039) 49.66( 0.77) 52.2( 2.9) 46.3 & 4.6 0.69 & 0.1 1 * Outlier6'28 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL.9 Table 7 Results (mean & 95% confidence limits) for Human Serum SRM 909 Element ICP-MS Certified value Lithium (pg m1-l) Cadmium (ng ml-') 1 1.45( 1 1.1 8-1 1.80) 'Li 11.66 k 0.28 'I2Cd 1.124 & 0.090 'I4Cd 1.19 f 0.1 3 '"Pb 18.98f0.52 1.24( 1.15- 1.34) Lead (ng ml- ') 20.0( 17.9-22.5) Table 8 Ultra-trace element concentrations (ng ml-') in normal human serum Element Li B Mo Sn Sb c s Ba Pb Bi Hg Concentration 0.60 0.20( 0.25-0.87) 13.9 6.9(4.1-25.8) 0.61 f 0.17( 0.30-0.86) 1.02 f 0.26(0.66-1.46 j 0.137 & 0.028( 0.095-0.165 j 0.70f 0.12(0.50-0.96) 1.04 & 0.65(0.23-2.35) < 0.20-0.71 < 0.10-0.71 < 0.007-0.067 No.of persons 12 12 12 12 6 12 16 12 12 19 Literature values 0.2-44 8.3-48.1 0.28-1.17 0.4-350 0.01-3.1 0.45-2.06 < 30-1900 0.05-4.8 0.02-14.5 0.1-6.0 and 33%) it does not limit the RSD on the measurements (between 1.6 and 4.1%) as the blank signal originates mainly from impurities present in the reagents and is therefore fairly stable. For normal human serum a range between 4.1 and 25.8 ng ml-' with a mean B concentration of 13.9 ng ml-' was found which is in good agreement with literature values (8.3-48.1 ng ml-I). Besides ICP-MS the only technique that can determine accurately the low levels of B in human serum is NA-MS.55 The determination of B in human serum and other biological materials has been discussed in more detail in a previous p~blication.~' Molybdenum Determinations of Mo were made at m/z 98 Cg8Mo (24.1%)].It must be emphasized that neither 95Mo (15.9%) nor 97Mo (9.5%) can be used as both nuclides suffer from spectral overlap respectively from 79Br160 + and 40Ar39K160+ 9 a nd ''Brl60+ and 40Ar41K'60+.56 A mean Mo concentration of 7.51 ng g-' was obtained (corresponding to 0.68 ng ml-' for liquid serum) which is in excellent agreement with the certified value. For the certification only NAA was used. The RSD on the measurements is about lo% mainly owing to the important contribution of the blank signal to the total signal in human serum (between 7 and 20%). The RSD is however comparable with that obtained by NAA. For normal human serum a range between 0.30 and 0.86 ng ml-' with a mean Mo concentration of 0.61 ngml-' was found which is in agreement with the value of 0.6 ng ml-' reported by Versieck and Cornelis.'2 Cadmium Cadmium has eight stable nuclides lo6Cd (1.25%) '"Cd (12.2%) 'I4Cd (28.7%) and '16Cd (7.5%).Some of these are interfered with isobarically '12Cd is interfered with by '12Sn (0.90/) "'Cd (12.5%) "'Cd (12.8%) '12Cd (24.1%) '13Cd (0.97%) '13Cd by '131n (4.3%) '14Cd by '14Sn (0.65%) and '16Cd by '%n (14.5%). Since In is used as an internal standard the use of 'I3Cd is excluded. In addition as the Sn concen- tration in human serum is between 0.40 and 0.64 ng ml-1,57 the contribution of Sn to the Cd signals at m/z 112 114 and 116 in human serum is not negligible. Therefore '16Cd cannot be used. Determinations were made at m/z 110 111 112 and 114 (Table 6). In general it can be stated that for all four nuclides good agreement with the certified value is obtained.The RSD on the measurements is relatively high (between 8.2 and 38.8%) mainly due to the important contribution of the blank signal to the signal for Cd in serum (between 30 and 60%). For '12Cd and '14Cd the isobaric overlap from Sn was corrected for by calculating the contribution of the Sn nuclides at m/z 112 and 114 respectively using the signal intensity for 12'Sn and the natural isotopic abundances for the Sn isotopes involved. Additional proof of the accurate correction of the isobaric overlap with the Sn nuclides is given by the analysis of Human Serum SRM 909 (Table 7). It should be noted that the concentration of Cd in this reference serum is about a factor of 7 higher than that found for the 'second-generation' biological reference material Freeze-Dried Human Serum (0.18 ng ml-' for liquid serum).The latter is in agreement with the concentration expected in normal human serum.12 Versieck and Vanballenberghe4 reported a range between < 0.105 and 0.192 ng m - ' of Cd. In order to perform accurate determinations of Cd it is necessary to get maximum sensitivity (at least a count rate of 3 x lo5-5 x lo5 for 100 ng ml-I of In). This was however not always attainable and varied from day to day. For that reason determinations of Cd in human serum could not always be carried out and therefore no study on the concentration of Cd in normal human serum was performed. Several studies are underway in order to overcome this problem. Flow injection whereby undiluted serum can be measured and electrothermal volatilization with extremely low absolute detection limits are the most promising techniques.In addition the use of a modified high-performance interface was evaluated With this interface a sensitivity of up to 2 x lo6 (for 100 ng ml-' of In) can be reached. Tin Determinations were made at m/z 118 C118Sn (24.2%)] and 120 ["'Sn (32.6%)] 9.925033 ng g-' for "'Sn and 9.77 +OX8 ng g-' (95% confidence limits) for 12'Sn (approxi- mately 0.9ngml-' for liquid serum). These results are in reasonable agreement with the values obtained by ICP-MS and NAA. The RSD of the measurements varies from 3.4 to 9.7% whereas the contribution of the blank to the total signal in human serum is between 10 and 25%.For normal human serum a range between 0.66 and 1.46 ng ml-' with a mean Sn concentration of 1.02 ng ml-' was found. Literature values for the concentration of Sn in human serum are rather scarce and are high in comparison with the results obtained here. They range from <40 to 350 ng ml-'. Recently Versieck and Vanballenberghe57 reported a mean Sn concentration in human serum of 0.505 ng ml-' with a standard deviation of 0.096 ng ml-' (range 0.400-0.636 ng ml-') which is comparable with the results obtained in the present study. Probably the concen- tration of Sn in human serum has been overestimated in the past similar to that of V Cr and M o . ~ ~ Antimony Determinations of Sb were made at m/z 121 [12'Sb (57.3%)] and 123 [123Sb (42.7%)] 0.87k0.29 ngg-' for "'Sb and 0.76k0.42 ng g-' (95% confidence limits) for 123Sb (approxi- mately 0.075 ngml-' for liquid serum).The RSD of theJOUKNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 29 measurements is high (between 25 and 70%) due to the important contribution of the blank to the total signal in human serum (up to 60%) and to the fact that the concentration found is between the detection limit (3s 0.03 ng m1-l) and the determination limit ( ~ O S ' ~ 0.1 ng ml-'). The results can only be compared with those obtained with NAA. Since both results have a great uncertainty nothing can be said about the agreement. Literature data on the concentration of Sb in normal human serum are scarce. Versieck and Cornelis" mentioned a range between 0.5 and 1 ng ml - of Sb.More recently Minoia ef a/.'' reported a range between 0.01 and 3.1 ng ml-' of Sb which is in agreement with the range found in this work (0.095-0.165 ngml-' of Sb). It can be concluded that the possibility of performing accurate determinations of Sb in human serum depends on the actual sensitivity. As already mentioned previously this can vary from day to day. Caesiun1 Since Cs is mono-isotopic determinations were made at nil- 133 (133Cs) resulting in a mean Cs concentration of 10.20 ng g - ' (corresponding to 0.93 ng ml-' for liquid serum) which is in excellent agreement with the certified value. For certification only NAA was used. The RSD of the measurements varies from 2.7 to 7.6%. whereas the contribution of the blank to the total signal in human serum is between 2.7 and 7.6%. For normal human serum a range between 0.50 and 0.96 ng m-' with a mean Cs concentration of 0.70ngml-' was found which is in agreement with the concentration expected for normal human serum (about 1 ngml-').'2 It should be noted that up to now only NAA could be used for the determination of Cs in human serum. B m ii4ni Determinations of Ba were made at m/z 138 [13*Ba (71.7%)] resulting in a mean Ba concentration of 11.1 ngg-' (corre- sponding to 1.01 ng ml- for liquid serum).The RSD of the measurements varies from 3.3 to 7.5% whereas the contribution of the blank to the total signal in human serum is between 8 and 20%. No certified or indicative values are available. For normal human serum a range between 0.23 and 2.35 ng ml-' with a mean Ba concentration of 1.04 ng ml-' was found.Literature values on the concentration of Ba in human serum mainly obtained by NAA are rather scarce and are high compared with the results obtained here. They range from <30 up to 1900ng ml-'. Some of these values are a factor of 1000 higher than the range found in this work. The concentration of Ba in human serum has probably been overestimated in the past. hlercwj Since the concentration of Hg in human serum is very low determinations could only be made at m/z 200 [200Hg (23.1 YO)] and 202 ["'Hg (29.8%)]. The results obtained with both nuclides do not differ significantly from each other and are in good agreement with the certified value. The RSD of the measurements is relatively high (between 5.9 and 15.6%) mainly due to the important contribution of the blank to the total signal in human serum (between 25 and 40%).The analysis of sera from 12 healthy subjects provided a result for only four cases 0.35 (2 x) 0.54 and 1.35 ng ml-I. For the other cases the signal measured did not differ signifi- cantly from the blank signal. Literature data range from 0.05 to 4.8 ng m1-l. It is clear that in some cases the concentration of Hg is between the detection limit (3s 0.20 ng ml-') and the determination limit (lOs 0.60 ng ml-I) so that determinations of Hg in normal human serum are not always possible. L e d Determinations of Pb were made at mlz 208 ['O*Pb (52.4%)] resulting in a mean Pb concentration of 46.3 ng g - ' (corre- sponding to 4.21 ng ml-' for liquid serum).The RSD on the measurements varies between 1.5 and 5.6% whereas the contri- bution of the blank to the total signal in human serum is between 9 and 15%. No certified or indicative values are available. In order to check the accuracy of the proposed method Human Serum SRM 909 with a certified Pb content was analysed (Table 7). The results obtained are in good agreement with the certified value. Analysis of sera from 12 healthy subjects resulted in a detection limit (0.10 ng ml-') for seven cases. In addition the highest concentration of Pb found was about 0.7 ng ml- ' which is a factor of 6 lower than that in the 'second-generation' biological reference material Freeze-Dried Human Serum. Literature values for the concentration of Pb in normal human serum mainly obtained by ETAAS and isotope dilution MS are rather scarce and contradictory.12 They range from 0.02 to 14.5 ng ml-'.Contamination with Pb from the air reagents etc. can introduce an important error when low concentrations of Pb have to be determined. Bism ti t h Since Bi is mono-isotopic determinations were made at rn/z 209 ('09Bi) resulting in a mean Bi concentration of 0.69 ng g - ' (corresponding to 0.063 ng ml-' for liquid serum). The RSD of the measurements varies from 5.7 to 13.6% whereas the contribution of the blank to the total signal in human serum is between 7.5 and 20%. No certified or indicative values are available. Analysis of sera from 19 healthy subjects results in a detection limit (0.007 ng m1-l) in ten cases.The highest concen- tration found was 0.067 ng ml-'. Literature data which are scarce range from 0.1 to 6 ng ml-'. Normal concentrations of Bi and levels after the intake of a therapeutic dose of colloidal bismuth subcitrate have been discussed in more detail in a previous p~blication.~' Conclusion It has been shown in this work that apart from Fe Co Cu Zn Br Rb Sr and I ICP-MS is able to determine the following ultra-trace elements in the 'second-generation' biological refer- ence material Freeze-Dried Human Serum Li B Mo Cd Sn Sb Cs Ba Hg Pb and Bi. For Cd Sb and to a lesser extent Bi some reservations must be made. The actual sensitivity is the limiting factor for these elements. Studies are underway to overcome this problem by using FI or electrothermal volatiliz- ation instead of pneumatic nebulization as a means of sample introduction.Extrapolation of these conclusions to normal human serum is not applicable to all the elements because the concentration for some of these e.g. Pb is significantly higher in the reference serum than in normal human serum. Moreover the concentration of these elements in normal human serum is not far above the detection level so that in some cases only a detection limit is obtained. If accurate and precise determinations are to be performed maximum sensitivity must be attained. This situation can be achieved by optimization of the nebulizer gas flow rate and the electrostatic lens settings using the signal of the internal standard. In addition for the determination of ultra-trace elements only a small mass range can be scanned so that the measuring time is used optimally for each element.Finally an internal standard with a mass close to that of the analyte must be used in order to correct for matrix effects. Furthermore,30 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 since the contribution of the blank is not negligible in the determination of ultra-trace elements in human serum only the most pure reagents can be employed. For Li Mo Sn Cs Ba and Bi the contribution of the blank was shown to be between 10 and 20% whereas for B Cd Sb Hg and Pb this could rise to more than 30%. The origin of the blank signal varies from element to element. Apart from the continuous background which is more or less constant over the whole mass range impurities present in the reagents or the argon gas (for B Sn Ba Hg and Pb) contribute to the observed blank signal. Accurate correction is possible with a blank solution containing 0.14 moll-' HN03 and the internal standard.It can be concluded that with the method developed here which includes a simple and short sample preparation followed by rapid determination with a high sample throughput a great number of elements that can be determined by ETAAS INAA or RNAA can also be determined by ICP-MS. The elements with a mass between 40 and 80u form an exception V Cr Mn Co Ni and As are spectrally interfered with and cannot therefore be determined accurately after a simple dilution of the serum samples6 "V suffers from interference from 35C1160+ 52Cr from 35C1160H+ and 40Ar'2C+,55Mn from 37C1180 + and 39K160+ 59C0 from 43Ca160+ and 36Ar23Na+ 60Ni from 23Na37C1+ and 75As from 40Ar35C1+. A more extensive sample preparation including separation of the matrix or the use of alternative sample introduction systems such as electrothermal volatilization is necessary.An example is the determination of As in human serum after the separation of C1 by an anion exchanger.61 As can be deduced from this work ICP-MS in combination with the optimized procedure yields for some elements such as Li Sn Ba Pb and Bi concentrations in normal human serum which until now have been more or less unknown. Therefore ICP-MS is a good alternative and/or a complementary technique to NAA and ETAAS. Grateful acknowledgement is made to L. Vanballenberghe for her contribution to the preparation of the serum samples.Thanks are also due to C. Vandecasteele for his interest in the work and to F. Vanhaecke for evaluating the manuscript. The PlasmaQuad was acquired by a grant from the Fund for Medical Scientific Research (FGWO). 1 2 3 4 5 6 7 8 9 10 11 12 13 14 References Versieck J. Hoste J. Barbier F. Vanballenberghe L. De Rudder J. and Cornelis R. Clin. Chim. Acta 1987 87 135. Versieck J. Hoste J. Barbier F. Steyaert H. De Rudder J. and Michels H. Clin. Chem. 1978 24 303. Cornelis R. Versieck J. Mees L. Hoste J. and Barbier F. J. Radioanal. Chem. 1980 55 35. Versieck J. and Vanballenberghe L. in Trace Elements in Man and Animals eds. Mills C. F. Bremmer I. and Chesters J. K. 1985 vol. 5 Commonwealth Agricultural Bureaux Farnham Royal p.650. Xilei L. Van Renterghem D. Cornelis R. and Mees L. Anal. Chim. Acta 1988 211 231. Halls D. J. and Fell G. S . Anal. Chim. Acta 1981 129 205. Veillon C. Patterson K. Y. and Bryden N. A. Anal. Chim. Acta 1984 164 67. Lewis S. A. O'Haver T. C. and Harnly J. M. Anal. Chem. 1985 57 2. Andersen J. R. Gammelgaard B. and Reimert S. Analyst 1986 111 721. Slavin W. J . Anal. At. Spectrom. 1986 1 281. Ericson S. P. McHalsky M. L. and Jaselskis B. Talanta 1987 34 271. Versieck J. and Cornelis R. Trace Elements in Human Plasma or Serum CRC Press Boca Raton Florida 1988. McLaren J. W. Beauchemin D. and Berman S . S. Anal. Chem. 1987 59 610. Beauchemin D. McLaren J. W. Willie S. N. and Berman S . S. Anal. Chem. 1988 60 687. 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 Lyon T.D. B. Fell G. S. Hutton R. C. and Eaton A. N. J . Anal. At. Spectrom. 1988 3 265. Ridout P. S. Jones H. R. and Williams J. G. Analyst 1988 113 1383. Satzger R. D. Anal. Chem. 1988 60 2500. Vanhoe H. Vandecasteele C. Versieck J. and Dams R. Anal. Chem. 1989,61 1851. Friel J. K. Skinner C. S. Jackson S. E. and Longerich H. P. Analyst 1990 115 269. Schmit J.-P. Youla M. and Gelinas Y. Anal. Chim. Acta 1991 249 495. Wiederin D. R. Smyczek R. E. and Houk R. S. Anal. Chem. 1991 63 1626. Lyon T. D. B. Fell G. S. McKay K. and Scott R. D. J. Anal. At. Spectrom. 1991 6 559. Gelinas Y. Youla M. Beliveau R. Schmit J.-P. and Ferraris J. Anal. Chim. Acta 1992 269 115. Vanhoe H.J. Trace Elem. Electrolytes Health Dis. 1993 in the press. Ward N. I. Durrant S. F. and Gray A. L. J. Anal. At. Spectrom. 1992 7 1139. Abou-Shakra F. R. Havercroft J. M. and Ward N. I. Trace Elem. Med. 1989 6 142. Tothill P. Matheson L. M. Smyth J. F. and McKay K. J. Anal. At. Spectrom. 1990 5 619. Vaughan M.-A. Baines A. D. and Templeton D. M. Clin. Chem. 1991 37 210. Lasztity A. Viczian M. Wang X. and Barnes R. M. J . Anal. At. Spectrom. 1989 4 761. Nygren O. Vaughan G. T. Florence T. M. Morrison G. M. Warner I. M. and Dale L. S. Anal. Chem. 1990 62 1637. Viczian M. Lasztity A. and Barnes R. M. J. Anal. At. Spectrom. 1990 5 293. Wang X. Lasztity A. Viczian M. Israel Y. and Barnes R. M. J. Anal. At. Spectrom. 1989 4 727. Serfass R. E. Thompson J.J. and Houk R. S. Anal. Chim. Acta 1986 188 73. Smith F. G. Wiederin D. R. Houk R. S. Egan C. B. and Serfass R. E. Anal. Chim. Acta 1991 248 229. Mulligan K. J. Davidson T. M. and Caruso J. A. J. Anal. At. Spectrom. 1990 5 301. Baumann H. Fresenius' J. Anal. Chem. 1990 338 809. Vanhoe H. Van Allemeersch F. Versieck J. and Dams R. Analyst 1993 118 1015. Dean J. R. Ebdon L. and Massey R. J. Anal. At. Spectrom. 1987 2 369. Delves H. T. and Campbell M. J. J. Anal. At. Spectrom. 1988 3 343. Campbell M. J. and Delves H. T. J. Anal. At. Spectrom. 1989 4 235. Vandecasteele C. Vanhoe H. and Dams R. J. Anal. At. Spectrom. 1993 8 781. Park C. J. Smith D. C. and Vanloon J. C. Trace Elem. Med. 1990 7 103. Vandecasteele C. Vanhoe H. Vanballenberghe L. Wittoek A. Versieck J.and Dams R. Talanta 1990 37 819. Vandecasteele C. Vanhoe H. Dams R. and Versieck J. Anal. Lett. 1990 23 1827. Versieck J. Vanballenberghe L. De Kesel A. Hoste J. Wallaeys B. Vandenhaute J. Baeck N. Steyaert H. Byrne A. R. and Sunderman F. W. Anal. Chim. Acta. 1989 204 63. Vanhaecke F. Vandecasteele C. Vanhoe H. and Dams R. Mikrochim. Acta 1992 108 41. Schmit J. P. and Chtaib M. Can. J. Spectrosc. 1987 32 56. Vaughan M. A. and Horlick G. Spectrochim. Acta Part B 1990 45 1301. Tanner S. D. Spectrochim. Acta Part B 1992 47 809. Vanhoe H. Vandecasteele C. Versieck J. and Dams R. Anal. Chim. Acta 1991 244 259. Vanhoe H. Vandecasteele C. Versieck J. and Dams R. Anal. Chim. Acta 1993 281 401. Vanhoe H. Versieck J. Vanballenberghe L. and Dams R. Clin. Chim. Acta in the press. Abou-Shakra F. R. 1990 personal communication. Baumann H. 1989 personal communication. Iyengar G. V. Clarke W. B. and Downing R. G. Fresenius' J . Anal. Chem. 1990 338 562.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 31 56 Vanhoe H. Goossens. J.. Moens L. and Dams R. J . A d . At. Spectrom.. submitted for publication. 57 Versieck J. and Vanballenberghe L. Anal. Chem. 1991 63 1143. 58 Versieck. J. and Cornelis R. Anal. Chim. Acta 1980 116. 217. 59 Currie L. A. A n d . Chem. 1968 40 586. 60 Minoia. C. Sabbioni E.. Apostoli P.! Pietra R. Pozzoli L. Gallorini. M.. Nicolaou G. Alessio L.. and Capodaglio E. SL'I'. 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ISSN:0267-9477    

DOI:10.1039/JA9940900023

出版商:RSC    

年代:1994

数据来源: RSC

摘要:

JOURNAL O F ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 33 Determination of Arsenic Species in Fish by Directly Coupled High- performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry* Simon Branch Les Ebdont and Peter O'Neill Plymouth Analytical Chemistry Research Unit Department of Environmental Sciences University of Plymouth Drake Circus Plymouth UK PL4 8AA Using directly coupled high performance liquid chromatography-inductively coupled plasma mass spec- trometry non-toxic arsenobetaine was identified as the major arsenic species in cod dab haddock mackerel plaice and whiting. The fish was caught in coastal waters around Plymouth UK and purchased from local markets. Arsenic levels ranged between 1.0 mg kg-' dry mass in the mackerel to 187 mg kg-' dry mass in the plaice.Mackerel also contained dimethylarsinic acid (DMAA) and possibly a lipid bound arsenic species. Levels of the toxic inorganic species were low in all cases. No monomethylarsonic acid was recorded in any of the fish. No degradation of arsenobetaine to more toxic species was observed when an enzymic digestion procedure based on the action of trypsin was applied to the fish with the possible exception of one of the plaice samples for which DMAA was characterized in the digest at the mg kg-' level. For total arsenic determinations nitrogen addition ICP-MS was used to overcome the potential interference from 40Ar35CI +. The results obtained compared well with certified values for the dogfish reference material DORM-1. Keywords Inductively coupled plasma mass spectrometry; high-performance liquid chromatography; arsenic speciation; fish; arsenobetaine Fish and marine-based products are the major source of arsenic in the human diet.'*2 Since the turn of the ~ e n t u r y ~ .~ fish and shellfish have been known to contain relatively high levels of arsenic being in excess of 1 mg kg-'. In 1926 Chapman4 proposed that the arsenic compound in lobster was a low toxicity organic molecule. However it was not until 1977 that Edmonds et d5 identified the molecule as arsenob- etaine a compound that is now known to be widely distributed in marine organisms.G12 Although the total arsenic concen- tration in fish and shellfish from UK waters has been deter- mined,2 little attempt has been made to identify the nature of the arsenic species present.Furthermore in the many studies of arsenic species in fish few have addressed the problem of quantifying the species. The analytical approach in the majority of arsenic speciation studies involves the coupling of the separatory powers of liquid chromatography with the inherent selectivity and sensitivity of atomic spectrometry. Gas chromatography cannot be used without derivatization as a number of species such as arsenob- etaine are non-volatile. The most common couplings are high- performance liquid chromatography (HPLC) with hydride generation atomic absorption spectrometry (HGAAS),'3-15 HPLC-inductively coupled plasma atomic emission spec- trometry ( ICP-AES),16-'8 and HPLC-electrothermal atomic absorption spectrometry ( ETAAS).lS2' Although these methods are satisfactory they all suffer certain disadvantages.22 Hydride generation AAS can only be applied to a limited number of applications since some of the major arsenic species eg.arsenobetaine are non-reducible. The principal problem with ICP-AES is that it does not have the required sensitivity for environmental analysis particularly as the arsenic wave- lengths are in the low UV region. Electrothermal AAS offers the required sensitivity for the determination of arsenic and responds to all arsenic species. However an elaborate interface is usually required to introduce the sample into the cuvette. Real time analysis is impossible owing to the furnace cycle hence discontinuous chromatograms are obtained. Ebdon * Presented in part at the 1993 Winter Conference on Plasma t To whom correspondence should be addressed.Spectrochemistry Granada Spain January 10-15 1993. et have reviewed coupled techniques for the speciation of arsenic. Recently the coupling of HPLC with inductively coupled plasma mass spectrometry (ICP-MS) has received interest in speciation No complicated interfacing is required HPLC flow and ICP-MS uptake rates are compatible and for arsenic high sensitivity to all species is attainable. Continuous chromatograms are also produced. The application of HPLC-ICP-MS to the determination of arsenic species in marine fish caught from the waters around Plymouth Devon UK is described in this paper. Experimental Materials and Methods Duplicate samples of fish were purchased from Plymouth Fish Market.The vendor prepared the fish as for a conventional customer. In the laboratory each fish was cut into small pieces and freeze dried (Edwards Super Modulyo Edwards High Vacuum Crawley Sussex UK). The dried fish was then ground in a pestle and mortar until a fine powder was produced and the powder was stored in a desiccator until required for analysis. Total arsenic was determined by accurately weighing 0.1-0.2 g of the fish sample into a poly(tetrafluoroethy1ene) digestion bomb (Savillex Corporation Minnetonka MN USA) and adding 2 ml of nitric acid (Aristar grade Merck Poole Dorset UK). The samples were left to pre-digest overnight and were then digested in a microwave oven. The digests were diluted to 10 or 100 ml with doubly de-ionized water (Millipore Bedford MA USA) which was used throughout.The samples and appropriate matrix matched standards were spiked with a solution (100 pg 1-') of indium (Aldrich AAS standard Aldrich Milwaukee USA) and ana- lysed by ICP-MS with addition of nitrogen to the injector gas (N,-ICP-MS) using the operating conditions shown in Table 1. The technique of N,-ICP-MS has recently been shown to overcome the interference of chloride on arsenic determinations by ICP-MS.29 A dogfish reference material (DORM-1 Canadian Research Council Ottawa Canada) was simul- taneously analysed to maintain quality control. Arsenic species34 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 Table 1 Instrumental parameters for the HPLC-ICP-MS coupling HPLC parameters - Mobile phase Flow rate Injection volume Run time ICP-MS parameters - Nebulizer gas flow rate Coolant gas flow rate Intermediate gas flow rate Forward power Reflected power Data acquisition mode survey scan Equilibration on 1 mmol 1-' K,SO pH 10.5.Switched on injection or after 3 mins to 50 mmol 1-' K2S04 pH 10.5 1.5 ml min-' 175 pl 671 s 0.85 1 min-' 14 1 min-' 0.8 1 min-' 1.5 kW <low Local mass set to 75 u in the fish were determined following two different extraction procedures. Method 1 was a variation on the method pre- viously described by Beauchemin et and Method 2 was based on the principle of enzymic digestion reported by Crews et aL31 Method 1 A 1.0 g-portion of the dry sample was accurately weighed into a glass beaker and 20 ml of methanol and 10 ml of chloroform were added (both Aristar grade Merck).After covering the sample was sonicated for 1 h. The solution was transferred into a centrifuge tube and centrifuged for 10min at 2500 rev min-'. The supernatant was transferred into a 100 ml separating funnel and the process was repeated on the remain- ing pellet. Chloroform (20 ml) and water (20 ml) were then added to the combined supernatants in the separating funnel which was shaken vigorously. The chloroform layer was run off and the water-methanol layer was filtered (Whatman 541 paper Whatman Kent UK) into a 100ml round-bottom flask The solvent was rotary evaporated and the residue was re-dissolved in 10 ml of water. The samples were further filtered using a 0.45 pm pore size filter (Millipore) into plastic storage bottles prior to analysis by HPLC-ICP-MS.The samples were refrigerated at 4°C if there was a delay in the final analysis. Recovery experiments and determinations of arsenic in the solid residue and the chloroform layer were also performed on representative samples. Method 2 A 1.Og portion of sample was accurately weighted into a plastic centrifuge tube along with 100mg of trypsin (Sigma Dorset UK). Ammonium carbonate solution (20 ml 0.1 mol l-' AnalaR Merck) was added the tube was sealed and placed in a shaking water-bath for 4 h at 37 "C. The sample was then ultracentrifuged at 11 000 rev min- for 20 min (MSE Highspeed 18 MSE Scientific Instruments Crawley Sussex UK). As with Method 1 the samples were filtered and refriger- ated prior to analysis by HPLC-ICP-MS.Recovery tests were performed and representative residues analysed for total arsenic concentration. Arsenic species were determined in the extracts using HPLC-ICP-MS. The HPLC separation has previously been describedz7 and involves separation of five species on a column (12.5 x0.4cm id.) packed with a strong anion- exchange resin (7-10 pm SAX Benson Reno NV USA). The column was immersed in a 60°C water-bath to improve peak shape. The HPLC system was interfaced to the ICP-MS by connecting the column outlet to the ICP-MS nebulizer by the shortest possible length of capillary tubing. Dilute solutions of alkaline potassium sulfate (Aristar Merck) were used as the mobile phase. Arsenic standards were freshly prepared from 1000 mg 1-1 As stock solutions of sodium arsenite (AnalaR) disodium hydrogen arsenate ( AnalaR Merck) dimethylarsinic acid (DMAA) (Sigma) monomethylarsonic acid (MMAA) (donated as disodium methanearsonate by Dr.A. Howard Southampton University Southampton UK) and arsenobetaine (AB) (donated by Professor K. J. Irgolic Texas A and M University TX USA). Instrumentation The ICP-MS measurements were performed using a VG Plasmaquad 2 ICP mass spectrometer (VG Elemental Winsford Cheshire UK) fitted with a high solids nebulizer (Ebdon nebulizer PSA Sevenoaks Kent UK). This arrange- ment overcame slight problems of salt deposition seen around the orifice of a glass concentric nebulizer supplied with the instrument. Chromotographic separations utilized a Waters 6000A pump (Waters Milford MA USA) with a Rheodyne 7125 (Rheodyne Cotati CA USA) injection valve used for sample introduction. Results and Discussion The moisture content of the various fish are shown in Table 2.In most cases the results for two separate fish are presented and these are represented by (1) and (2) in the table. All the fish with the exception of the mackerel contained greater than 70% water. The lower result for the mackerel may be related to the oily nature of the fish. Arsenic species in the various fish obtained using the two extraction procedures are shown in detail in Tables 3 and 4. No arsenite or MMAA were identified in any of the samples. The total arsenic concentration in pairs of fish of the same species were similar to each other the one exception being lemon sole. It is interesting that the two cod specimens one coming from the Atlantic the other from the local waters around Plymouth had markedly different arsenic concen- trations.Other workers6.' have also noted that the arsenic content of the same species of fish varies with the location of the catch. This is tentative evidence to support the theory of Edmonds and France~coni~~ that arsenobetaine does not arise within higher marine animals endogenously but is derived from microbial action upon algae within sediments releasing arsenobetaine to the water column. Therefore fish from differ- ent areas may contain differing concentrations of arsenobetaine as the products of microbial action will vary from site to site. The flatfish surveyed in the study i.e. dab plaice and sole were found to contain the highest levels of arsenic.All of these fish are carnivorous bottom feeders existing on diets of mol- luscs and bivalves which filter feed on the sea bed. Thus they are more likely to ingest arsenobetaine before it is dissipated in the body of the ocean. It is also possible that the variation Table 2 Moisture content of fish in % m/m Fish Atlantic Cod 'Local' cod Dab Haddock Lemon Sole Mackerel Plaice Whiting Moisture content 86 86 74 73 77 76 77 60 63 81 74 70 75JOURNAL OF ANALYTICAL ATOMIC SPECTKOMETRY JANUARY 1994 VOL. 9 35 Table 3 Arsenic species extracted by Method 1 (methanoi-chloroform extraction). All results in mg kg ~ ' of dry mass Sample Atlantic cod 'Local' cod Dab (1) Dab ( 2 ) Haddock Lemon Sole ( 1 ) Lemon Sole ( 2 ) Mackerel (1 1 Mackerel ( 2 ) Plaice (1) Plaice (2) Whiting ( 1 ) Whiting (2) DORM-] * Total arsenic 17.8 k0.7 13.7 F 0.7 27.1 & 0.7 28.3 5 0.4 30.7 & 0.2 62.2 & 2.8 172.952.6 149.65 15.1 4.1 50.5 3.5 k 0.3 196.1 5 3.5 183.1 5 1.6 15.9 0.5 16.4 k 0.2 AB 15.1 k0.6 13.2 rfr 0.6 3 1.2 & 0.8 26.9 k 1.9 27.5 5 1.8 59.3 k 2.1 145.6 rt 12.8 102.6f 19.4 1.1 k0.3 1.OkO.1 187.3 k 20.3 102.9 k 13.6 10.45 1.8 9.8 -+_ 0.7 DMAA N P t < 0.3 < 0.3 < 0.3 < 0.3 < 0.5 < 0.5 < 0.5 0.550.1 0.3 f 0.i < 0.5 < 0.5 < 0.3 < 0.3 Arsenate N P < 0.5 < 0.5 < 0.5 < 0.5 < 1.0 < 0.5 < 0.5 < 0.5 1.1 k0.S < 1.0 < 1.0 < 0.5 < 0.5 Total As in residue N P 0.6 f 0.01 1.3 50.01 N P NP 2.5 5 0.04 N P N P 0.5 F 0.03 0.5 * 0.02 NP NP NP N P Total As in methanol water phase NP 12.0 k0.1 22.5 & 0.8 NP NP 53.4f 1.1 N P NP 1.5 f 0.8 2.0 k 0.2 NP NP NP NP Total As in chloroform phase NP 0.09 & 0.0 1 0.3 5 0.03 NP NP < 0.05 NP NP 0.08 * 0.0 1 : 0.08 f 0.01 : N P N P NP NP * Certificate values for DORM-1 AB = 15.7 k 0.8 mg kg-'; total arsenic = 17.7 k 2.1 mg kg -' .i.NP = Not performed. : These results should be regarded as 'water-leachable' arsenic. Table 4 Arsenic species extracted by Method 2 (trypsin digestion). All results in mg kg-.' of As dry mass Sample Atlantic cod Local cod Dab (1) Dab ( 2 ) Haddock Lemon Sole ( 1 ) Lemon Sole (2) Mackerel ( 1 ) Mackerel ( 2 ) Plaice ( 1 ) Plaice ( 2 ) Whiting ( 1) Whiting ( 2 ) DORM- 1 * Total arsenic 17.8 k 0.7 13.7 k 0.7 27.1 f 0.7 28.3 & 0.4 30.7 * 0.2 61.2 k 2.8 172.9 2.6 149.6 k 15.1 4.1 k0.5 3.5 -t- 0.3 196.1 53.5 183.1 5 1.6 15.9 k 0.5 16.4 k 0.2 AB 16.1 k0.4 13.5 k0.9 26.9 & 1.2 40.0 5.7 41.4 k0.4 50.0 k 2.1 183.2 k 14.1 77.0 k0.2 0.8kO.l 0.2 k 0.01 106.0 k 19.0 77.0 k 5.0 12.lf0.2 15.8 f 1.3 DMAA NPt < 0.5 t 0 .5 ~ 0 . 5 < 0.5 < 0.5 < 0.5 < 0.5 0.4 k 0.1 0.4 k 0.1 <0.5 21.6 k 2.3 < 0.5 < 0.5 Arsenate NP < 1.0 1.0k0.4 2.4 k 0.3 < 1.0 < 1.0 < 1.0 < 1.0 0250.1 0.3 k 0.1 < 1.0 < 1.0 I .3 k0.2 < 1.0 Total As in residue NP 2.3k0.1 3.7 -t 0. I NP NP 15.7 k 0.2 NP NP 2.8 & 0.2 1.4 & 0.2 NP NP NP NP Total As in extract NP 13.2 * 0.6 29.6 k 2.0 NP NP 8.0 i 3.0 N P NP 2. I * 0.2 2.3 &- 0.1 NP NP NP NP * Certificate values for DORM-I AB= 15.7+0.8 mg kg-'; total arsenic= 17.7F2.1 mg kg-' t NP = Not performed.in arsenic concentrations might be related to other factors such as age or health status. The concentrations of arsenic in some of the fish were relatively high e.g. in plaice over 180 mg kg-' dry mass. These concentrations are not unprecedented. Luten et found the arsenic concentration in plaice from various regions of the North Sea to be in the range 3-166 mg kg-l. These values are higher than reported in the UK Ministry of Agriculture Fisheries and Food (MAFF) arsenic surveillance paper,2 which listed results in the range 1-20 mg kg-' fresh mass. The results for cod dab and haddock in this study also compare well with those detailed in the MAFF report. The mackerel results in this study 3.5-3.4mg kg-' dry mass compared well with results of surveys of fish from Scottish waters,2 the results for which lay in the range 0.2-1.6 mg kg-' fresh mass.The results of this study for cod haddock mackerel and sole are similar to results for the same fish caught in the Atlantic6 Luten et reported arsenic concentrations in lemon sole of 24.9-31.4 mg kg-' fresh mass. which compared well with the values from this study of 150-173 mg kg-' dry mass. Using both extraction methods arsenobetaine was found to be the major species present in all of the fish. In a number of specimens eg. the cod samples. arsenobetaine comprised approximately 100% of the arsenic. In a few cases the total arsenic remaining in the residue was determined by N2- ICP-MS. The results confirmed that the extraction procedures had recovered the majority of the arsenic.Total arsenic was also determined in the extract solutions and found to offer only moderate agreement with the sum of the species. There was some evidence to suggest that this was due to the methanol in the extract causing perturbation in the ICP-MS. Attempts to matrix-match samples and standards proved fruitless. Similarly arsenic was determined in the chloroform phase of selected specimens and low results were obtained. The results for the mackerel specimens were of interest. Following extraction by Method 1 (Table4) the sum of the individual species the arsenic in the extracted residue and the arsenic in the chloroform phase was less than the total arsenic determined in the original fish.This was almost certainly because the mackerel an oily fish contains a significant proportion of arsenic bound to lipids. This arsenic would be extracted into the chloroform layer. The chloroform was evaporated to leave a viscous orange phase. The solid was insoluble in water. After shaking the water was itself analysed by ICP-MS to give the figure in the 'total arsenic in CHCI phase' column in Table 4 which in this case would be more accurately described as 'water-leachable' arsenic. Attempts to digest the solid with nitric acid proved unsuccessful owing to sample charring. If a proportion of the arsenic in mackerel were lipid bound it might explain why low recoveries were recorded for mackerel using Method 2. Trypsin a protease would be unable to break down such a compound.As the sum of the individual species was less than the total arsenic in the extract e.g. 1.4 and 2.1 mg kg-' respectively for mackerel ( l ) this might indicate that some of the lipid- bound arsenic was extracted but remained bound to the36 JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 column. During the analyses the column had to be periodically reversed and flushed in order to overcome pressure build-up due to the accumulation of material on the column. The discrepancy between the sum of the arsenic species and the total arsenic determined by ICP-MS for lemon sole plaice and whiting may be indicative of the fish containing arsenic in a lipid-bound form. In planned future studies the determination of arsenic in all residues and chloroform layers will assist in elucidating the nature of the speciation. Using extraction Method ( l ) DMAA was identified only in the mackerel and at toxicologically insignificant concen- trations.The level of arsenate in mackerel (2) is of more significance although it would still be less than 1 mg kg-' in the fresh fish. The results for the trypsin extractions produced a number of peculiarities. It was predicted prior to the study that trypsin would yield greater recoveries than the methanol-chloroform approach as the protease would disrupt the lipid-protein membrane and release the cell contents. This hypothesis was supported by the results for DORM-1 and the whiting which gave higher results for Method 2. However both plaice both mackerel and one of the lemon sole samples gave lower recoveries in the extracts.This may have been related to the composition of the fish tissues. The haddock results indicate only about 80% of the arsenic was extracted from the fish tissue the predominant species again being arsenobetaine. The results for the dab with extraction Method 2 were unsatisfactory. Arsenobetaine recoveries were in excess of 130% of the total arsenic figure. This was a reproducible phenomenon observed in both fish. Why this occurred is unclear. The dab was unique in that it was the only fish in which an unidentified species appeared on the chromatogram (see Fig. 1). Co-injection showed it not to be any of the five species in the study. The species was not identified in the extracts obtained using Method 2 and it could be that the species co-eluted with arsenobetaine giving an erroneously high result.Further work to identify this arsenic compound is planned. A high concentration of DMAA was recorded in one of the plaice. This was possibly owing to partial enzymic degradation of the arsenobetaine by trypsin. The sum of the two species correlates well with the speciation in the same fish using methanol-chloroform extraction. The results of the determinations in no case yielded inorganic arsenic results with implications for human health. The highest arsenate level recorded was 2.4 mg kg-' but as these results 7450 3725 c I v) v) c r O ; 1000 1. C c)) m .- 500 0 I I I Ti rne/s 335 67 1 Fig. 1 (a) HPLC-ICP-MS chromatogram of a mixed arsenic stan- dard 1 arsenobetaine; 2 DMAA; 3 arsenite; 4 MMAA; and 5 arsen- ate.(b) HPLC-ICP-MS chromatogram of a methanol-chloroform extract from Dab (1) showing the presence of unidentified species 1 arsenobetaine; 2 unknown species; and 3 arsenate were for dry mass the exposure would be less than 1 mg kg-' in the fresh fish. Quality control experiments were performed throughout the study. Experimental results for DORM-1 were in good agree- ment with certified values for total arsenic and arsenobetaine concentrations. The slightly higher value for arsenobetaine by Method 2 in comparison to the certificate value probably arose as the certificate value is quoted for arsenobetaine extracted by Method 1. The recoveries of individual species taken through extraction Method 1 using plaice as the sample matrix varied from 80% for arsenobetaine to 108% for arsenate.The recovery of spikes taken through extraction Method 2 and using whiting as the sample matrix varied between 85% for arsenobetaine to 115% for arsenate. Determination of arsenic in plaice (1) using standard additions gave a recovery of 190 mg kg-' dry mass or 97%. For all of the samples peak identity was confirmed by co-injection of individual standards. Conclusions The technique of directly coupled HPLC-ICP-MS has been shown to be useful in the investigation of arsenic species in fish. In the fish studied the predominant arsenic compound present was non-toxic arsenobetaine. The concentrations of the toxic inorganic species arsenite and arsenate were neglible or below the limits of detection in all of the fish analysed.Since these are amongst the most commonly eaten fish these are significant results when assessing dietary risk. We gratefully acknowledge the financial support of the UK Ministry of Agriculture Fisheries and Food for this research. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 References Penrose W. R. CRC Crit. Rev. Environ. Control 1974 4 465. Survey of Arsenic in Food Food Surveillance Paper Number 8 Her Majesty's Stationery Office London 1982. Cox H. E. Analyst 1925 50 3. Chapman A. Analyst 1926 51 548. Edmonds J. S. Francesconi K. A. Cannon J. R. Raston C . L. Skelton B. W. and White A. H. Tetrahedron Lett. 1977,18 1543. Lawrence J. F. Michalik P. Tam G. and Conacher B. S. J. Agric. Food Chem. 1986 34 315. Francesconi K.A. Micks P. Stockton R. A. and Irgolic K. J. Chemosphere 1985 14 1443. Edmonds J. S. and Francesconi K. A. Chemosphere 1981 10 1041. Luten J. B. Riekwel-Booy G. and Rauchbaar A. Environ. Health Perspect. 1982 45 165. Hanoaka K. and Tagawa S. Bull. Jap. SOC. Sci. Fish. 1985 51 681. Morita M. and Shibata Y. Anal. Sci. 1987 3 575. Hanaoka K. Yamamoto H. Kawashima K. Tagawa S. and Kaise T. Appl. Organomet. Chem. 1988 2 371. Ricci G. R. Shepard L. S. Colovos G. and Hester N. E. Anal. Chem. 1981 53 610. Tye C. T. Haswell S. J. O'Neill P. and Bancroft K. C. C. Anal. Chim. Acta 1985 169 195. Chana B. S. and Smith N. J. Anal. Chim. Acta 1987 197 177. Morita M. Uehiro T. and Fuwa K. Anal. Chem. 1981,53 1806. LaFreniere K. E. Fassel V. A. and Eckels D. E. Anal. Chem. 1987 59 879.Low G. K.-C. Batley G. E. and Buchanan S . J. Chromatographia 1986 22 292. Brinckman F. E. Blair W. R. Jewett K. L. and Iverson W. P. J. Chromatogr. Sci. 1977 15 493. Brinkman F. E. Jewett K. L. Iverson W. P. Irgolic K. J. Ehrhardt K. C. and Stockton R. A. J. Chrornatogr. 1980,191,31. Haswell S . J. Stockton R. A. Bancroft K. C. C. O'Neill P. Rahman A. and Irgolic K. J. J. Autom. Chem. 1987 9 6. Ebdon L. Hill S. Walton A. P. and Ward R. W. Analyst 1988 113 1159.JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY JANUARY 1994 VOL. 9 37 23 Dean J. R. Munro S. Ebdon L. Crews H. M. and Massey R. J. Anal. At. Spectrom. 1987 2 607. 24 Thompson J. J. and Houk R. S. Anal. Chem. 1986 58 2541. 25 Shibata Y. and Morita M. Anal. Sci. 1989 5 107. 26 Beauchemin D. Siu K. W. M. McLaren J. W. and Berman S. S. J. Anal. At. Spectrom. 1989 4 285. 27 Branch S. Bancroft K. C. C. Ebdon L. and O’Neill P. Anal. Proc. 1989 26 73. 28 Hansen S. H. Larsen E. H. Pritzl G. and Cornett C. J. Anal. At. Spectrom. 1992 7 629. 29 Branch S. Ebdon L. Ford M. Foulkes M. E. and O’Neill P. J. Anal. At. Spectrom. 1991 6 151. 30 Beauchemin D. Bednas M. E. Berman S. S. McLaren J. W. Siu K. W. M. and Sturgeon R. E. Anal. Chem. 1988 60 2209. 31 Crews H. M. Burrell J. A. and McWeeney D. J. Z. Lebensm. Unters Forsch. 1985 180 221. 32 Edmonds J. S. and Francesconi K. A. Appl. Organomet. Chem. 1988 2 297. 33 Luten J. B. Riekwel-Booy G. Greef J. v. d. and ten Noever de Brauw M. C. Chemosphere 1983 12 131. Paper 3102642 F Received May 10 1993 Accepted September 6 1993

ISSN:0267-9477    

DOI:10.1039/JA9940900033

出版商:RSC    

年代:1994

数据来源: RSC