ISSN:0003-2654    

DOI:10.1039/AN99318BP027

出版商:RSC    

年代:1993

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN99318FX033

出版商:RSC    

年代:1993

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN99318BX035

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, SEPTEMBER 1993, VOL. 118 107N Book Reviews The Dynamics of Electrophoresis By R. A. Mosher, D. A. Saville and W. Thormann. Electrophoresis Library Series. Edited by 6. J. Radola. Pp. xv + 236. VCH. 1992. Price DM186.00; f70.00 ISBN 3-527-28379-X (VCH, Weinheim); 1-56081 -1 92-7 (VCH, New York). This book is dedicated to our colleague and friend Milan Bier. In the Introduction many pages are used to define history, without giving overwhelming information on references of the past. An overview of the historical research, that grounded modern electrophoresis, gives young scientists especially a guideline to find their way in the literature. Too often it is thought that the leading figures of today are the leading figures of the past. In this book it is shown that the new generation is taking over the role of those who made and created the electrophoretic techniques.In the classification of the electrophoretic methods it is shown that four basic principles (with and without electro- phoretic flow) exist. As is well known, these four basic principles can be carried out with any electrophoretic appar- atus. With such equipment one can separate small ions, anions, cations, amino acids, even peptides, proteins, DNA and RNA molecules and restriction fragments. In the two- dimensional mode it is important to know that various electrophoretic principles can be combined. It will be clear that such combinations will increase the information output of researchers. This book clearly describes what kind of prin- ciples have to be chosen or which combination.It is, therefore, of importance that techniques such as two-dimen- sional GC-MS , pulsed flow and micellar electrokinetic chromatography are described. In the ‘simplest’ forms of electrophoresis such as zone electrophoresis (ZE), isotacho- phoresis (ITP) , micellar electrokinetic chromatography (MEC) and liquid chromatography with isoelectric focusing (LC-IEF) it is rather ‘simple’ to devise computer programs for both qualitative and quantitative purposes. A very good reader guide to overview this book is given on page 4. Chapter 2 discusses the physico-chemical background of electrophoresis. It not only gives attention to electrophoresis, but also to colloid chemistry. A good compromise is found between the well-established theory and the current possibili- ties of using computer programs for evaluation and under- standing of the data obtained.This chapter is especially recommended to those scientists who would like to become experts in the field of electrophoresis. In Chapter 3, sophisticated computer modelling is given, both to understand the programs used and to add specific wishes for those who are trained in soft- and hardware. These programs are checked with experimental data obtained with the so-called CapScan equipment. For most scientists this chapter is difficult, because for one reason or another ‘wet-chemistry’ and ‘colloid chemistry’ no longer feature in the standard university education package. It is, therefore, a pity that so many beautiful analytical ‘separation’ techniques have to disappear.For this reason this book is extremely useful for physical , analytical and biochemists. Such informa- tion must at least be available in the laboratory. In Chapter 4, moving boundary electrophoresis is des- cribed, as introduced by Arne Tiselius. Although it does not have a great analytical importance, the background of this technique has to be understood. It is the separation phase of ITP used especially for injecting samples in gel filled columns. Chapter 5 describes zone electrophoresis. This principle is probably the most used separation technique in, for example, slab gels, paper, cellulose acetate and in capillary tubes in free solutions and in gels. In free solutions this principle can be used with and without electroosmotic flow (EOF). A clear view of various effects is given.Hybrid forms of CZE and ITP illustrate that sharpening up effects and concentrating effects due to ITP and CZE make it important to understand the background of these principles. In Chapter 6 isotachophoresis is described. It will be clear that this technique now has a great potential, because commercial equipment has become available. Again it is important to understand the background of this technique, to use it for sharpening up the sample before zone electro- phoresis is started. This is comparable to the so-called Ornstein and Davis technique, published in 1964. The computer modelling has been checked with real experiments with the apparatus. In Chapter 7 isoelectric focusing is described. Information is given to select the pH gradient needed (wide or narrow).Sometimes just one kind of carrier ampholyte is rec- ommended, sometimes a mixture. The reproducibility of this technique is dependent on the reproducible material (ampholytes) produced batch-to-batch, week-to-week, month-to-month and year-to-year. In this reviwers’ opinion this chapter is very important for the scientists in companies manufacturing these ampholytes. Chapter 7.6 is of particular importance for students on undergraduate courses, but also for Ph.D. students in the fields related to these techniques. More attention could have been paid to the immobilized pH gradient (Chapter 7.2.2, pages 217-221), while the focusing of proteins in natural pH gradients is questionable (Chapter 7.8, pages 221-229). This book should be available in any laboratory.The information given is comprehensive and will last forever. The equations can be given in classical mathematics or, for instance, in fluid dynamics. The theory behind the principles of electrophoresis is well established, and needs to be known by those scientists who wish to develop their own electrolyte systems in order to optimize their separations. Fruns M . Everuerts Particle Size Analysis Edited by N. G. Stanley-Wood and R. W. Lines. Pp. xx + 538. Royal Society of Chemistry. 1992. Price f57.50. ISBN 0-851 86-487-2. This book covers the proceedings of the 25th Anniversary Conference of the Particle Characterization Group of the Analytical Division, Royal Society of Chemistry, held at the University of Technology, Loughborough in September 1991.Now, if you want to know ‘where particle characterization is at present’ and ‘where it is going’, then this is the book for you. It does not, of course, forget its roots and is also a good review of the development of particle analysis over the past 25 years; indeed some of the well tried and tested methods used over this period of time are discussed in some of the contributed papers. This book is published under the subject classifications of analytical and industrial chemistry, instrumentation and chemical engineering. The wide ranging relationship that particle characterization has with these topic areas is more than adequately served by the 58 papers that make up the publication. A subject index, which allows you to browse through this ever increasing branch of science, is provided; although X for X-ray instrumentation does not seem to make it into the index, it is certainly included in the text!108N ANALYST, SEPTEMBER 1993, VOL.118 The first paper is a fine scene setter and considers the philosophy/fundamentals of particle characterization, its development over 25 years and where this development might lead us. Like the first paper, each contribution is a nugget, critically addressing, in many cases, the underlying theory of a particular instrumental or particle characterization technique, its advantages, limitations of use or performance and in a number of papers future trends. The comprehensive nature of this book makes it difficult to say exactly who it is aimed at in terms of level.In some cases it is not for the mathematically squeamish and seems to lean towards the deeper research level, whereas other papers are suitable for undergraduates in their quest for background information. This is not a criticism, more a consequence of the way in which this science has progressed, and continues to progress. The topics under discussion include surface area, porosity and pore structure, particle shape, field-flow fractionation, clectrical sensing, sedimentation, two-dimensional sieve cas- cadography and a range of light- and laser-based particle sizinghhape techniques. The numerous contributions con- cerning the latter include applications of the more advanced techniques of diffraction, scattering, Doppler velocimetry, obscuration/extinction and photon correlation spectroscopy.Mathematical approaches to particle characterization, such as three-dimensional particle reconstruction, packing, fractal gcometry, principal component analysis, particle morphology and shape change, are also discussed. Examples of applica- tions with an industrial bias are fairly well served. In these days of quality assured techniques, thankfully the need for standards is never in question. Hence, calibration and certified reference materials are an indispensable part of particle characterization. Several papers discuss this area in a critical and open manner. A knowledge of the limitations of a technique gives a balanced view and allows the scientist to determine the confidence of data obtained. Although this information is presented it is noted that sometimes the optimism of an interested author creeps in.This aside, certainly industrial establishments as well as academic institutions should place this timely publication on their library shelves. Mike Foulkes Haaland’s topic is ‘Multivariate Calibration Methods Applied to the Quantitative Analysis of Infrared Spectra’. He gives a good comparison of the variety of multivariate approaches to this problem. A practical example based on the industrially important problem of quality control of boro- phosphosilicate glass is also presented. Windig gives some practical industrial examples of the use of chemometric techniques in the solution of problems from Raman, FTIR microscopy and pyrolysis mass spectrometry. The technique used for the examples is the SIMPLISMA approach of self-modelling mixture analysis.One data set discussed is again a glass process, the other is a rubber triblends problem. Naes and Isaksson present an excellent view of the use of principal components regression in near-infrared, concentrat- ing on the assessment of the predictive capability. Computer-Assisted Mass Spectral Interpretation: MS-MS analysis is covered by Hart and Enke. They describe work based on a combination of database techniques, pattern recognition and automated rule generation. Meuzelaar and co-workers report work on Canonical Correlation Analysis of Multisource Fossil Fuel Data, where the spectroscopic techniques used are mass spectrometry, pyrolysis-field ionization MS and photoacoustic FTIR. Cor- relation of such multisource data is one of the strengths of the chemometric approach, this worked example will be useful to those new to the field.Harrington reports on the use of fuzzy rule based expert systems in laser ionization MS of polymer thin films. The other chapters on the PAIRS knowledge based system for interpret- ing infrared spectra, Hadamard methods in signal recovery and the report on the work of Munk on the use of NMR spectra in structure elucidation build on several previous publications. Signal processing in ion mobility spectrometry and multi- channel atomic emission spectroscopy are covered in the final two chapters. Overall the work is well presented but suffers from the lack of state-of-the-art reports. The print and paper of the book are of high quality, but the spine of the book is glued rather than stitched, which leads to the pages becoming detached after a short time.R. A . Hearmon Computer-Enhanced Analytical Spectroscopy. Volume 3 Edited by Peter C. Jurs. Modern Analytical Chemistry Series. Pp. xvi + 320. Plenum. 1992. Price US$175.00. ISBN 0-306-43859-3. How to Use Reverse-Phase HPLC By Gabor Szepesi. Pp. x + 356. VCH. 1992. Price DMI 68.00; f63.00. ISBN 0-89573-766-3 (VCH Publishers); 3-527-27939-3 (VCH Verlagsgesellschaft). This is the third book of proceedings of the excellent Snowbird series of symposia on the application of computers in analytical spectroscopy. As with all conventionally produced symposia proceedings the book suffers somewhat in the gap between the meeting and the publication of the proceedings. The reported lectures were presented at the third symposium that was held in 1990, the fourth symposium in the series has since been held in 1992.Thus it is important for the proceedings to conform to the editors aim that they ‘provide a cross-section of current research activities in this important and active field’. Most spectroscopic techniques are men- tioned. The texts concentrate on chemometrics, knowledge- based systems and signal processing, rather than attempting to cover the full range that the title might imply. The proceedings are presented as 11 chapters by the speakers. Some of these take the form of general overviews or comparisons of methods, others cover specific examples. The highlights of the proceedings are the chapters by Haaland and Windig.This book contains seven chapters on various aspects of reversed-phase HPLC although in places it goes outside of this subject encompassing other HPLC modes such as ion- exchange, size-exclusion and intermediate-polarity phases, but, surprisingly, includes nothing on the use of graphitized carbon packings apart from a passing mention in the Introduc- tion. The book is probably most suitable for analysts with some reasonable experience of HPLC and who require an introduction to the more specialized topics included in later chapters. Chapter 1 presents some advantages and disadvantages of straight-phase versus reversed-phase chromatography. Chapter 2 consists of a summary of basic HPLC theory followed by a survey of different separation modes.The former section is poorly presented and this reviewer would certainly not recommend it as a training aid for inexperienced chromatographers. The latter section seems irrelevant for a book devoted to reversed-phase chromatography, although it would appear from the presentation that the author considersANALYST, SEPTEMBER 1993, VOL. 118 ROYAL SOC,ETY CHEM,STRY To Order, Please write to: Royal Society of Chemistry, Turpin Distribution Services Ltd, Blackhorse Road, Letchworth, Herts SG6 IHN, UK. or telephone (0462) 672555 quoting your credit card details. We accept Access/VisalMasterCard/Eurocard. Turpin Distribution Services Limited is wholly owned by the Royal Society of Chemistry. For information on other books and journals, please write to: Royal Society of Chemistry, Sales and Promotion Dept., Thomas Graham House, Science Park, Milton Road, Cambridge CB4 4WF, UK.RSC Members should obtain members prices and order from: The Membership Affairs Department at the Cambridge address above. @- && _~ information Services I 109N ion-exchange and size-exclusion modes to be reversed-phase met hods. Chapter 3 discusses stationary phases providing quite a nice review of different packings from different sources, the importance of variations in parameters such as pore size, particle size, nature of bonded alkyl chains, extent of phase coverage, etc. Polymeric-based phases and chiral packings are discussed as well as further considerations of ion-exchange, and size-exclusion phases. Chapter 4 is concerned with mobile phases and discusses solvent selectivities, approaches to problems of polar adsorptions at residual silanol sites using mobile-phase additives, e.g. , competing amines, ion-suppres- sion techniques and ion-pair reagents. However, the author then goes on to discuss a number of aspects of column performance, which although useful, should be included in the previous chapter on columns. The final three chapters were considered to contain the most valuable contributions in this publication. Chapter 5 discusses some special techniques. The section on ion-pair chromatography includes useful material on how various factors influence chromatographic performance. This is fol- lowed by reasonable sections on chiral chromatography, indirect detection methods, mu1 ticolumn methods and peptide separations.Chapter 6 provides a good review of optimization techniques and includes practical examples for applying such methods and checking expert systems. The final chapter is a topical discussion on method validation and in which the most valuable section is a very interesting approach to the deter- mination of ruggedness. This book contains several interesting topics and most chapters provide a good selection of references, which are usually reasonably recent. However, it is spoiled by poor presentation of material in many sections sometimes due to badly expressed ideas and sometimes due to grammatical errors. Either way, readers are likely to find these sections difficult to understand. In addition, many diagrams and tables were poorly prepared in some cases rendering them incom- prehensible and a number of typographical errors were found. G. P. R. Curr ROYAL SOCIETY OF CHEMISTRY Quality Assurance for Analytical Laboratories Edited by: M. Parkany International Organisation for Standardization, Geneva At the present time, when public opinion is demanding accountability of laboratories carrying out analyses related to socially sensitive issues, such as drug testing, blood alcohol monitoring, HIV-testing, water and air purity, acid rain, etc., the importance of harmonizing protocols for quality assurance schemes cannot be over-emphasized. The first step in obtaining the status of ‘Certified in Accordance with...’, is for a laboratory to make a full and detailed internal evaluation, and this invaluable new book will assist you in that step. Quality Assurance for Analytical Laboratories shows how to introduce internal quality assurance schemes that can form the basis for third party assessment, certification and accreditation. It gives real-life examples from a wide range of laboratories, illustrates the statistical tools needed and details the correct terms and their definitions. It also contains a list of all relevant International Standards. For those laboratories wishing to establish a self-audit for checking conformity with the IS0 9000 series, this book is a must. Special Publication No. 130

ISSN:0003-2654    

DOI:10.1039/AN993180107N

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

110N ANALYST, SEPTEMBER 1993, VOL. 118 Conference Diary Date Conference October 3-7 4-8 5-7 5-7 5-8 5-8 8-13 10-15 11-13 11-15 13 16-17 17-21 17-22 17-23 18-22 19-20 Location 10th Asilomar Conference on Mass Spectrometry [TOF-MS] USA Estes Park, CO, ECASIA 93,5th European Conference on Catania, Applications of Surface and Interface Analysis Italy 34th ORNL-DOE Conference on Analytical Chemistry in Energy Technology Laboratory Exhibition and Conference 5th Meeting of the Nuclear Magnetism and Biology Group 4th ISEC. Fourth International Seminar on Electroanalytical Chemistry 5th BCEIA. Fifth International Beijing Conference and Exhibition on Instrumental Analysis Electrochemical Society Meeting VIth National Symposium on Mass Spectometry Gatlinburg, TN, USA London, UK Toulouse , France Beijing, China Beij ing , China New Orleans, LA, USA Dehradun, India Optical Sensing for Environmental Monitoring Atlanta, GA, Symposium USA FT Microscopy-10 Years On: 4th European Seminar on FT-IR Microscopy UK Manchester, Second National Conference on Inductively Coupled Plasma Mass Spectrometry USA Detroit, MI, Eighth Symposium on Separation Science and Oak Ridge, TN, Technology for Energy Application USA FACSS XX, 20th Annual Meeting of the Detroit, MI, Federation of Analytical Chemistry and USA Spectroscopy Societies 10th International Symposium on Gw at t/Thun , Biorecognition and Affinity Technology Switzerland Modern Electrochemistry in Industry and for the Protection of the Environment Krakow , Poland Frederick Conference on Capillary Electrophoresis USA Frederick, MD , Con tact Laszlo Tokes, Syntex Discovery Research, 3401 Hillview Avenue, Palo Alto, CA 94304, USA TeI: + 1 415 855 5713.Fax: + 1 415 354 7363 G. Marletta, Consorzio Catania Ricerche, V. Le Andrea Doria, 6, 1-95125 Catania, Italy Tel: +39 95 221635. Fax: +39 95 339734 W. R. Laing, Technical Program Chairman, Oak Ridge National Laboratory, P.O. Box 2008, MS 6127, Oak Ridge, TN 37831-6127, USA Tel: +1 615 574 4852. Fax: +1 615 574 4902 Evan Steadman Communications Group Ltd., 90 Calverley Road, Tunbridge Wells, Kent, UK TN12UN Professor M. Malet-Martino, Laboratoire IMRCP, Universite Paul Sabatier, 118, route de Narbonne, F-31062 Toulouse Cedex, France Professor Erkang Wang, 109 Sitalin Street, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, China General Service Office, 5th BCEIA, Room 5412, Building No.4, Xi Yuan Hotel, Er Li Gou, Beijing 100046, China Electrochemical Society Inc, 10 South Main Street, Pennington, NJ 08534-2896, USA Dr. Pradeep Kumar, Indian Institute of Petroleum, Dehradun-248 005, India, and Dr. S. K. Aggarwal, Honorary Secretary-ISMAS, c/o Fuel Chemistry Division, Bhabha Atomic Research Centre, Bombay-400 085, Maharastra, India Adrianne Olsakovsky, 3 Gateway Center, 4 West, Pittsburgh, PA 15222, USA Tel: +1412 232 3444. Fax: +1412 232 3450 Michelle Barker, Conference Co-Ordinator , Spectra-Tech Europe Limited, Genesis Centre, Science Park South, Birchwood, Warrington, UK WA3 7BH Tel: +44 (0) 925 830 250. Fax: +44 (0) 925 830 252 Society for Applied Spectroscopy/ICP/MS Users Group, 198 Thomas Johnson Drive, Suite-2, Frederick, MD 21702-4317, USA Tel: +1 301 694 8122.J. T. Bell, Oak Ridge National Laboratory, Post Office 2008, Oak Ridge, TN 37381, USA FACSS, 198 Thomas Johnson Drive, Suite S-2, Fredericks, MD 21702, USA Tel: + 1 301 846 4789. Fax: + 1 301 694 6860 Professor A. N. Eberle and Mrs. D. Affentranger, Department of Research, University Hospital, CH- 4031 Basle, Switzerland Tel: +41 61 2652 324. Fax: +41 61 2652 350 Dr. Andrzej Kowal, Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapiminajek 1, 30-239 Krakow, Poland Margaret L. Fanning, Conference Coordinator, PRI, NCI-FCRDC, P.O. Box B, Frederick, MD Tel: +1 301 846 1089. Fax: +1 301 846 5866 21702-1201, USAANALYST, SEPTEMBER 1993, VOL.118 11lN Date 19-23 20-22 21-22 24-28 25-29 26-28 Conference EXPOQUIMIA '93: Applied Chemistry Technical Fair Hygiene and Health Management in the Working Environment ~ ~~~~~ Location Barcelona, Spain Ghent, Belgium International Conference on Analytical Chemistry, Biochemistry and Pharmaceutical Sciences 8th Symposium on Separation Science and Technology for Energy Applications Scanning Electron Microscopy Field Emission and X-ray Microanalysis The 1993 Analytical Forum-'Meeting the Challenge' November 1-3 2 2-4 3 3-5 7-10 7-1 1 7-12 8-10 11-12 Chernyaev Conference on Chemistry, Analysis, Technology and Application of Platinum Metals Electro-Membrane Processes KEMIA 93. Finnish Chemical Congress and Exhibition Pharmaceutical Applications and Sample Handling Techniques 2nd International Symposium on Characterization and Control of Odours and VOC in the Process Industries Electrophoresis '93 7th International Forum-Electrolysis in Chemical Manufacture Casablanca, Morocco Gatlinburg, TN, USA Ellenville, NY, USA Chepstow, UK Moscow, Russia London, UK Helsinki, Finland York, UK Louvain-la-Neuve , Belgium Charleston, SC, USA Lake Buena Vista, FL, USA Symposium on Supercritical Fluid Phenomena St.Louis, MO , (1993 Annual Meeting of the AIChE) USA International Symposium on Plasma PolymerizatiodDeposition USA Las Vegas, NV, International Conferences on Analytical Chemistry, Biochemistry, Pharmaceutical India Sciences, and Water Quality/Environmental Pollution New Delhi, Contact Fira de Barcelona, Avda.Reina Ma Cristina, 08004 Barcelona, Spain 3rd International Symposium, 'Hygiene and Health Management in the Working Environment', c/o TI-K VIV, Attn. Ms. Rita Peys, Desguinlei 214, B-2018 Antwerp, Belgium Dr. V. M. Bhatnagar, Alena Chemicals of Canada, P.O. Box 1779, Cornwall, Ontario, Canada K6H 5v7 Tel: +1 613 932 7702. Dr. J. T. Bell, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6223, USA Tel: +1 615 574 4934; or Dr. J. S. Watson, K-25 Plant, P.O. Box 2003, Oak Ridge, TN 37831-7298, USA Tel: +1 615 574 6795. Dr. Angelos Patsis, Center of Materials Science, State University of New York, New Paltz, NY 12561, USA Tel: +1 914 257 3800. Lisa Butler, Analytical Products Group, Hewlett- Packard Ltd., Cain Road, Bracknell, Berkshire, UK RG12 1HN Dr.I. B. Baranovsky, Kurnakov Institute of General and Inorganic Chemistry, 31 Lenin Avenue, Moscow 117907, Russia Dr. T. R. Ralph, Johnson Matthey Technology Centre, Blounts Court, Sonning Common, Reading, Berkshire, UK RG4 9NJJ Tel: +44 734 722811 ext. 2257. Fax: +44 734 723236 Ms. Anita Haatainen, Tel: +358 0 150 9207 or Mr. Seppo Niiranen Tel: +358 0 150 9215. Don Clark, Physical Sciences-265, Pfizer Central Research, Ramsgate Road, Sandwich, Kent, UK CT13 9NJ Tel: +44 304 616036. Fax: +44 304 616726 Symposium Secretariat, Societe Belge de Filtration, Universitk Catholique de Louvain, Voie Minckelers 1, 1348 Louvain-la-Neuve, Belgium Tel: +32 10 47 23 26. Fax: +32 10 47 23 21 Mrs. Janet Cunningham, Electrophoresis '93 , c/o The Electrophoresis Society, P.O.Box 279, Walkersville, MD 21793, USA Tel: +1 301 898 3772. Fax: +l 301 898 5596 Dr. N. Weinberg, 72 Ward Road, Lancaster, NY Tel: 1-1 716 684 0513. Fax: +1 716 684 0511 Michael A. Matthews, Chemical Engineering Department, University of Wyoming, Box 3295, University Station, Laramie, WY 82071-32, USA Tel: + 1 307 766 5769 Fax: + 1 307 766 4444. Or: Ted W. Randolph, Chemical Engineering Department, Yale University, 9 Hillhouse Avenue, New Haven, Tel: +1203 432 4375. Fax: +1203 432 7232 K. L. Mittal, Skill Dynamics (an IBM Company), 500 Columbus Ave., Thornwood, NY 10594, USA Tel: +l 914 742 5747. Fax: +1 914 742 5594 Dr. V. M. Bhatnagar, Alena Chemicals of Canada, P.O. Box 1779, Cornwall, Ontario, Canada K6H 5V7 Tel: +1 613 932 7702.14086-9779, USA CT 06520-2159, USA112N ANALYST, SEPTEMBER 1993, VOL. 118 Date 11-12 12-13 14-19 14-19 15-19 22-23 30-31 12 Conference 7th International Conference on Plasma Chemistry and Technology 5th Topical Conference on Quantitative Surface Analysis (ASSD Topical Conference) XV International Congress of Clinical Chemistry OPTCON '93 32nd Annual Eastern Analytical Symposium International Conferences on Analytical Chemistry, Biochemistry, Pharmaceutical Sciences, and Water QualityhZnvironmental Pollution 13th International Symposium on HPLC of Proteins, Peptides and Polynucleotides Location San Diego, CA, USA Clearwater Beach, FL, USA Melbourne, Australia San Jose, CA, USA New Jersey, USA Shanghai, China San Francisco, CA, USA Contact Research Institute of Plasma Chemistry and Technology, P.O.Box 1653, Carlsbad, CA 92008, USA Paul Holloway, University of Florida, 258A Rhines Hall, Gainesville, FL 32611, USA Tel: +1904 392 6664. Fax: +l 904 392 4911 1993 IFCC Congress Secretariat, 232 Bridge Road, Richmond, Victoria, Australia Tel: +61 3 429 4322. Fax: +61 3 427 0715 IEEE/LEOS, 445 Hoes Lane, P.O. Box 1331, Piscataway, NJ 08855-1331, USA Tel: +1 908 562 3896. Fax: +1 908 562 1571 EAS Program Committee, P.O. Box 633, Montchanin, DE 19710-0633, USA Dr. V. M. Bhatnagar, Alena Chemicals of Canada, P.O. Box 1779, Cornwall, Ontario, Canada K6H 5V7 Tel: + 1 613 932 7702. Ms. Paddy Batchelder, Conference Manager, 7948 Foothill Knolls Drive, Pleasanton, CA 94588, USA Tel: +1 510 426 9601. Fax: +l 510 846 2242 December 6-8 International Symposium on Purity Stockholm, Swedish Academy of Pharmaceutical Sciences, P.0. Determination of Drugs Sweden Box 1136, S-11181 Stockholm, Sweden 7-9 The First Conference in Chemistry and its Doha, Professor Abdel-Fattah M. Rizk, Department of Tel: +46 8 245085. Fax: +46 8 205511 Applications Qatar Chemistry, Faculty of Science, University of Qatar, 8-10 Laser M2P, Materials Engineering, Medicine Lyon, Richard MoncorgC, Universitk de Lyon 1, Biit. 205, P.O. Box 2713, Doha, Qatar and Biology, Physics and Chemistry France F-69622 Villeurbanne Cedex, France 1994 January 5-7 6th Winter Conference on Flow Injection Analysis 10-15 1994 Winter Conference on Plasma Spectrochemistry 11-14 19-21 5th International Symposium on Supercritical Fluid Chromatography and Extraction 2nd International Conference on Reactive Plasmas and 11th Symposium on Plasma Processing HPCE '94: Sixth International Symposium on High Performance Capillary Electrophoresis 31-3/2 San Diego, CA, USA San Diego, CA, USA Baltimore, MD, USA Yokohama, Japan San Diego, CA, USA Professor G.D. Christian, Department of Chemistry BG-10, University of Washington, Seattle, WA 98195, USA Tel: + 1 206 543 1635. Fax: + 1 206 685 3478 Dr. R. Barnes, 1994 Winter Conference on Plasma Spectrochemistry , % ICP Information Newsletter, Department of Chemistry, Lederle GRC Towers, University of Massachusetts, Amherst, MA 01003- 0035, USA Tel: +1 413 545 2294. Fax: +1 413 545 4490 Larry T. Taylor, Department of Chemistry, Virginia Polytechnic Institute, Blacksburg, VA 24061 , USA T.Goto, Department of Quantum Engineering, Nagoya University, Chikusa-ku, Nagoya 464-01, Japan The Symposium Manager, Shirley Schlessinger, 400 East Randolph Street, Suite 1015, Chicago, IL 60601, USA Tel: + 1 312 527 2011. February 13-17 Second International Glycobiology San Francisco, Paddy Batchelder, P.O. Box 370, Pleasanton, CA Symposium: Current Analytical Methods CA, 94566, USA USA Tel: +1510 426 9601. Fax: +1510 846 2242 21-25 OFC '94: Optical Fibre Communications San Jose, CA, Meetings Department, Optical Society of America, Conference USA 2010 Massachusetts Avenue, NW, Washington, DC 20036-1023 , USA Tel: + 1 202 223 9034. Fax: + 1 202 416 6100ANALYST, SEPTEMBER 1993, VOL. 118 113N Date Conference 23-25 HTC 3: Third International Symposium on Hyphenated Techniques in Chromatography 2 8 4 3 Pittcon '94: The 45th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy March 7-1 1 13-16 13-18 27-30 April 6-8 10-13 10-15 10-16 12-14 17-19 19-22 4th International Symposium on Trends and New Applications in Thin Films Third European Federation of Corrosion Workshop on Microbial Corrosion 207th American Chemical Society National Meeting Location Antwerp, Belgium Chicago, IL, USA Dresden, Germany Estoril, Portugal San Diego, CA, USA International Federation of Automatic Control Galveston, TX, (IFAC) Symposium on Modeling and Control USA in Biomedical Systems Electroanalysis: A Tribute to Professor J.D. R. Cardiff, Thomas UK ANATECH 94: 4th International Symposium on Analytical Techniques for Industrial Process Control France Mandelieu La Napoule , 207th ACS National Meeting and 5th Chemical Mexico City, Congress of North America (with Sessions of Mexico Analytical Chemistry, Environmental Chemistry, Chemical Health and Safety, etc.) 3rd International Conference on Methods and Kailua-Kona, Applications of Radioanalytical Chemistry Hawaii, USA 13th Pharmaceutical Technology Conference Strasbourg, France International Symposium on Volatile Organic Compounds (VOCs) in the Environment Montreal, Quebec, Canada ANALYTICA'94: 14th International Munich, Conference on Biochemical and Instrumental Analysis Germany Contact Dr. R.Smits, p/a BASF Antwerpen N.V., Central Laboratory, Scheldelaan, B-2040 Antwerp, Belgium Tel: +32 3 568 2831. Fax: +32 3 568 3250 Mrs.Alma Johnson, Program Secretary, The Pittsburgh Conference, Department CFP, 300 Penn Center Boulevard, Suite 332, Pittsburgh, PA 15235, USA Frank Richter, TU Chemnitz, FB Physik, PSF 964, D-09009 Chemnitz, Germany Fax: +49 371 852491 C6sar Sequeira, Instituto Superior Tkcnico, Av. Rovisco Pais, 1096 Lisboa Codex, Portugal, or A. K. Tiller, Corrosion Centre, 23 Grosvenor Gardens, Kingston-upon-Thames, UK KT2 5BE, or D. Thierry , Swedish Corrosion Institute, Roslagsvagen 101, Hus 25, S-10405 Stockholm, Sweden Department of Meetings, American Chemical Society, 11516th St., NW, Washington, DC 20036, USA Tel: +1 202 872 4396. IFAC Biomedical Symposium, University of Texas Medical Branch, Box 55176, Galveston, TX 77555- 5176, USA Tel: + 1 409 770 6628 or 770 6605.Fax: + 1 409 770 6825 Dr. J. M. Slater, Department of Chemistry, Birkbeck College, University of London, 29 Gordon Square, London, UK WClH OPP Tel: +44 71 380 7474. Fax: +44 71 380 7464 ANATECH 94 Secretariat, Elsevier Advanced Technology, Mayfield House, 256 Banbury Road, Oxford, UK OX2 7DH Tel: +44 (0)865 512242. Fax: +44 (0)865 310981 Mr. B. R. Hodson, American Chemical Society, 1155-16th Street N.W., Washington, DC 20036, USA Tel: + 1 202 872 4396. Ned A Wogman, Battelle, Pacific Northwest Laboratories, P.O. Box 999, P7-35, Richland, WA 99352, USA Tel: +1 509 376 2452. Fax: +1 509 376 2373 Professor Mike Rubinstein, 13th Pharmaceutical Technology Conference, 24 Menlove Gardens North, Liverpool, UK L18 2EJ Tel: +44 51 737 1993. Fax: +44 51 737 1070 Symposium Chairman, Dr.Wuncheng Wang, US Geological Survey, WRD, P.O. Box 1230, Iowa City, IA52244, USA. Tel: +1319 3374191, Fax: +1 319 354 0510; or Co-Chairmen, Dr. Jerald Schnoor, University of Iowa, Department of Civil and Environmental Engineering, Iowa City, IA 52242, USA. Tel: +1 319 335 5649, Fax: +1319 335 5777; and Dr. Jon Doi, Roy F. 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Fax: +1708 980 6698 AOCS EducatiodMeetings Department, P.O. Box 3489, Champaign, IL 61826-3489, USA Tel: + 1 217 359 2344. Fax: + 1 217 351 8091 Ms.J. E. Cunningham, Barr Enterprises, P.O. Box 279, Walkersville, MD 21793, USA Tel: +1301898 3772. Fax: +1301 898 5596 Meetings Department, Optical Society of America, 2010 Massachusetts Avenue, NW, Washington, DC Tel: +1202 223 9034. Fax: +1202 416 6100 Focus 94, P.O. Box 227, Buckingham, Buckinghamshire, UK MK18 5PN Tel: +44 2806 613. Fax: +44 2806 487 Dr. M. Malaiyandi, CAEC, Chemistry Department, Carleton University, 1255 Colonel By Drive, Ottawa, Canada K1S 5B6 Tel: + 1 613 788 3841. Fax: + 1 613 788 3749 Dr. James F. Lawrence, Food Additives and Contaminants, Health and Welfare, Tunney's Pasture, Ottawa, Ontario, Canada K1A OL2 Professor Salvatore Daniele, Department of Physical Chemistry, The University of Venice, Calle Larga, S. Marta 2137-1-30123 Venice, Italy Tel: +39 41 5298503.Fax: +39 41 5298594 Professor Terumichi Nakagawa, Symg Molecular Chirality (SMC) , Faculty o Pharmaceutical Sciences, Kyoto University, Yoshida-Shimoadachi-cho, Sakyo-ku, 606 Japan Fax: +81 48 471 0310 (Professor Hara) Professor B. Sarkar, Department of Biochemistry, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada M5G 1x8 60666-0507, USA 20036-1023, USA - on ASMS, 815 Don Gaspar, Santa Fe, NM 87501, USA Tel: + 1 505 989 4517. Dr. Alfred Christy, Department of Chemistry, University of Bergen, N-5007 Bergen, Norway Ari Ivaska, Abo Akademi University, Laboratory of Analytical Chemistry, Biskopsgatan 8, SF-20500 Abo Turku, Finland Kay Russell, Conference Department, Elsevier Advanced Technology, Mayfield House, 256 Banbury Road, Oxford, UK OX2 7DH Tel: +44 (0) 865 512242. Fax: +44 (0) 865 310981 Dechema, Theodor Heuss- Allee 25, P.0. Box 970146, D-W-6000 Frankfurt am Main 97, Germany A. 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Fax: +34 57 218606 Joseph Geller, Geller Microanalytical, 1 Intercontiental Way, Peabody, MA 01960, USA Tel: +1508 535 5595.ANALYST, SEPTEMBER 1993, VOL. 118 115N Date 15-18 16-17 16-17 19-24 27-117 Conference The Second International Symposium on Speciation of Elements in Toxicology and Environmental and Biological Sciences Location Loen, Norway 14th International Symposium on Environmental Pollution 18th International Conference on Analytical Chemistry and Applied Chromatography/ Spectroscopy 20th International Symposium on Chromatography Special FEBS Meeting on Biological Membranes July 18-22 XI11 International Congress on Electron Microscopy 20-22 Seventh Biennial National Atomic Spectroscopy Symposium August 2-6 The Second Changchun International Symposium on Analytical Chemistry(C1SAC) 8-12 IGARSS '94: 1994 International Geoscience and Remote Sensing Symposium Toronto, Canada Toronto, Canada Bournemouth, UK 21-26 208th ACS National Meeting (with Sessions of Analytical Chemistry, Environmental Chemistry, Chemical Health and Safety, etc ) 29-219 13th International Mass Spectrometry Conference Espoo , Suomi-Finland Paris, France Hull, UK Changchun, China Pasadena, CA, USA Washington, DC, USA Budapest, Hungary Con tact The Second International Symposium on Speciation of Elements in Toxicology and in Environmental and Biological Sciences, Yngvar Thomassen, National Institute of Occupational Health, P.O.Box 8149 DEP, N-0033 Oslo 1, Norway Dr. V. M. Bhatnagar, Alena Chemicals of Canada, P.O. Box 1779, Cornwall, Ontario, Canada K6H 5V7 Tel: +1 613 932 7702. Dr. V. M. Bhatnagar, Alena Chemicals of Canada, P.O. Box 1779, Cornwall, Ontario, Canada K6H 5V7 Tel: +1 613 932 7702. Mrs J. A. Challis, Chromatographic Society, Suite 4, Clarendon Chambers, 32 Clarendon Street, Nottingham, UK NG1 5JD Tel: +44 602 500596. Fax: +44 602 500614 Professor Timo Korhonen, Biochemical Society, European Federation of Biochemical Societies (FEBS) , Department of General Microbiology, University of Helsinki, Mannerheimintie 172, SF- 00300 Helsinki, Finland B.Jouffrey, SFME 67, rue Maurice Gunsbourg, 94205, Ivry sur Seine cedex, France Tel: +33 1 46702844. Fax: +33 1 46708846 Dr. Steve Hill, Department of Environmental Sciences, University of Plymouth, Drake Circus, Plymouth, Devon, UK PL4 8AA Professor Quinhan Jin, Department of Chemistry, Jilin University, Changchun 130023, China Tel: +86 431 82233 (ext. 2433). Fax: +86 431 823907 Meetings Department, Optical Society of America, 2010 Massachusetts Avenue, NW, Washington, DC Tel: + 1 202 223 9034. Fax: + 1 202 416 6100 Mr. B. R. Hodson, American Chemical Society, 115516th Street N.W., Washington, DC 20036, USA Hungarian Chemical Society, H-1027 Budapest, Hungary Tel: +36 1201 6883. Fax: +36 1 15 61215 20036-io23, USA September 5-9 7th International Symposium on Synthetic Tiibingen, Dechema, P.O. Box 970146, D-W-6000 Frankfurt am 11-16 EUCMOS XXII: XXIInd European Congress Essen, GDCh-Geschaftsstelle, Abt. Tagungen, Membranes in Science and Industry Germany Main 97, Germany on Molecular Spectroscopy Germany Varrentrappestr. 40-42, Postfach 90 04 40, D-6000 Frankfurt am Main 90, Germany Tel: +49 69 79 17 358. Fax: +49 69 79 17 475 12-15 Separations for Biotechnology Reading , SCI Conference Office, 14/15 Belgrave Square, UK London, UK SWlX 8PS Tel: +44 71 235 3681. Fax: +44 71 823 1698 Entries in the above listing are included at the discretion of the Editor and are free of charge. If you wish to publicize a forthcoming meeting please send full details to: The Analyst Editorial Office, Thomas Graham House, Science Park, Milton Road, Cambridge, UK CB4 4WF. Tel: +44 (0)223 420066. Fax: +44 (0)223 420247.

ISSN:0003-2654    

DOI:10.1039/AN993180110N

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

116N ANALYST, SEPTEMBER 1993, VOL. 118 Key Appointment to Boost Nottingham’ Trent’s Scientific Research Profile Professor Colin Creaser has been appointed Head of the Department of Chemistry and Physics at The Nottingham Trent University. He has joined Nottingham Trent from the University of East Anglia where he was Leader of the Analytical Chemistry Group. One of Professor Creaser’s key aims for the future is to develop and expand the department’s research activities. He is at the forefront of research in the field of ion trap mass spectrometry, a technique that enables the detection of trace amounts of environmental pollutants such as dioxins. It also allows the detection of substances such as veterinary drug residues in food samples. Professor Creaser’s team of post-graduate and post-doc- toral researchers from the University of East Anglia will also be joining the department later this summer, along with a team of four researchers from Brunel University.These moves will bring additional scientific equipment worth over &Yi million to Nottingham Trent. Commenting on his appointment, Professor Creaser said, ‘I am delighted to have joined Nottingham Trent at what is a very exciting and challenging time as it takes its place as one of the leading “new” universities’. ‘The Department of Chemistry and Physics here is already known for the quality of both its teaching and its research. I hope to build on the work currently underway, develop new areas of specialist interest and help raise the department’s profile in the national and international community’.Other priorities for Professor Creaser will be to build on the department’s strong record for forging international links and to develop more opportunities for students to focus on environmental themes in their courses. Born in Surrey, Professor Creaser was brought up in Uganda but returned to the UK to attend school in Bucking- hamshire and Sussex. After gaining his B.Sc. and Ph.D. at the University of Kent, he spent two years in the US conducting post-doctoral research at the University of California at Santa Barbara. On returning to the UK in 1978, he joined the Physico- Chemical Measurements Unit at the Harwell Laboratory, where he was responsible for the mass spectrometry service. Six years later he moved to the University of East Anglia. Professor Creaser is a member of the Royal Society of Chemistry and serves on the council of its Analytical Division.Future Issues will lnclude- Determination of Mercury Levels in Human Urine and Blood by Ultraviolet-Visible Spectrophotometry-Hiromi Aikoh and Takashi Shibahara Simultaneous Determination of Ammonia Nitrogen and L-Glutamine in Bioreactor Media Using Flow Injection- Bernhard 0. Palsson, Bing Q. Shen, Mark E. Meyerhoff and Marek Trojanowicz Rapid Screening of Fish Tissue for Polychlorinated Dibenzo- p-dioxins and Dibenzofurans-Thomas L. King, John F. Uthe and Charles J. Musial Determination of Phosgene (Carbonyl Chloride) in Air by High-performance Liquid Chromatography With a Dual Specific Detection System-Weh S. Wu and Virindar S. Gaind Measurement of the Sorption of Actinides on Minerals Using Microanalytical Techniques-Mark M.Cowper, John A. Berry, Hugh E. Bishop, Peter R. Fozard, John W. McMillan and Simon A. Mountfort Fluorescence Detection of the Glutathione S Conjugate With Aldehydes by High-performance Liquid Chromatography With Post-column Derivatization-Mitsuaki Sano, Masahiro Fujita, Kazunori Takeda and Isao Tomita Use of Pattern Recognition for Signatures Generated by Laser Desorption-Ion Mobility Spectrometry of Polymeric Materials-Michael Simpson, R. Saatchi, David R. Anderson, Cameron W. McLeod and Michael Cooke Reflux Pre-digestion in Microwave Sample Preparation- Helen J. Reid, Stanley Greenfield, Tony E. Edmonds and Rafiq M. Kapdi Determination of Trace Elements in Laboratory-reagent Grade Sodium Salts by Atomic Absorption Spectrometry and Inductively Coupled Plasma Atomic Emission Spectrometry After Preconcentration by Column Solid-phase Extraction- Anka Alexandrova and Sonja Arpadjan Inorganic Modifiers in Ion-pair Chromatographic Separation of Dicyanoaurate(1)-John J. Byerley, Emmanuel 0. Otu and Campbell W. Robinson Detection of Ephedrine and Phenylpropanolamine in Urine Using a Polarization Fluoroimmunoassay-David L. Colbert, Sergei A. Eremin, A. V. Smirnov, Gerard Gallacher and David S. Smith Comparison of Capillary Zone Electrophoresis With Standard Gravimetric Analysis and Ion Chromatography for the Determination of Inorganic Anions in Detergent Matrices- Emma L. Pretswell, Andrew R. Morrisson and John S. Park

ISSN:0003-2654    

DOI:10.1039/AN993180116N

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, SEPTEMBER 1993, VOL. 118 Under-determination of Strontium-90 in Soils Containing Particles Irradiated Uranium Oxide Fuel Deborah H. Oughton and B. Salbu Isotope and Electron Microscopy Laboratories, Agricultural University of Norway, 1432 As, Norway Tom L. Brand and J. Philip Day Department of Chemistry, University of Manchester, Manchester, UK M 13 9PL Asker Aa rkrog Environmental Science and Technology Department, Risaf National Laboratory, DK-4000, Denmark 1101 of A much used method for the determination of 90Sr in soil depends on extraction of the soil with 6 mol I-’ HCI, followed by P-counting. For soils containing particles of irradiated uranium oxide, we postulate that this extraction could result in a variable underestimate owing to incomplete chemical recovery of strontium from the uranium oxide matrix.In experiments on two soils, collected from near Windscale (now Sellafield) in 1956 and near Chernobyl in 1990, about 25% of the total 90Sr present in the soil was recovered in 24 h by HCI extraction at room temperature, and the presence of high-radioactivity particles both before and after extraction was demonstrated by autoradiography. For a further 11 particle-containing Chernobyl soils, 90Sr determination, based on classical HCI extraction, yielded, on average, 54% (range 3345%) of the total 90Sr, as determined by oxidative alkaline fusion. While we accept that HCI extraction is well established as a reliable method for the determination of soil 90Sr derived from weapons fallout, we conclude that more rigorous analytical pre-treatment is essential in instances where the 90Sr may be associated with fuel particles.Keywords: Strontium-90 determination; soil extraction; uranium oxide fuel particle; Windscale; Chernob yl Historically, on at least two occasions, particles of uranium oxide from irradiated reactor fuel have been released in significant amounts into the environment.1 In the early 1950s, the operation of the two Windscale piles (at Sellafield, UK) resulted in the continuous release over several years of an estimated 20 kg of uranium, in the form of relatively large particles (up to 700 pm in length) of oxidized uranium fuel.2 More recently, the Chernobyl Reactor accident, in 1986, released a large amount of radioactive particles .3-7 These varied in size, shape and composition, but were mainly of two types.Firstly, fragmentation of the reactor core during the initial explosion released about 3.5% of the irradiated uranium dioxide fuel: the larger fuel particles (20-400 pm) were deposited within about 60 km of the reactor, while smaller particles were carried at least 1500 km. Secondly, during combustion of the reactor core, following the explo- sion, small particles of irradiated fuel and ‘condensation’ particles (Le., inactive or active materials on which the volatile fission products had condensed) were released. These par- ticles were carried considerable distances from Chernobyl, and constituted the major component of long-lived fission products deposited at distances over 30 km (that is, outside the so-called ‘30 km exclusion zone’). The radiochemical analysis of soils containing discrete radioactive particles can present special problems, apart from the difficulty of obtaining representative samples.In direct y- ray spectrometry (e.g., for 137Cs), inhomogeneity could clearly give rise to errors in calibration, whereas for determi- nations requiring chemical isolation of the nuclides, for example, in the determination of 90Sr or actinides, problems arise if the analyte nuclide is not completely extracted (or, more precisely, in instances in which a yield monitor is used if complete exchange between the analyte and yield monitor nuclides is not achieved). Such problems have been recog- nized for some time, and the subject has been reviewed recently.8 In particular, Sill and co-workers9JO showed that, for soils containing particles of refractory uranium or pluto- nium oxides, extraction methods involving HCl and/or HN03, which would be appropriate for soils containing only weapons fallout, achieve very low recoveries (typically <30%) of plutonium and other actinides.In such instances, fusion techniques, resulting in complete dissolution of the sample, were recommended.10 In relation to 90Sr determination in soils containing fuel particles, a crucial part of the analytical procedure is the initial chemical extraction of the 90Sr from within the fuel particle matrix. Traditionally, the determination of 90Sr in soil has depended upon an extraction procedure using HCl, typically 6 mol 1-1 HCl at room temperature.llJ2 This extraction step, which was developed in the 1950s and remains a recommen- ded procedure ,8913 achieves good recovery of 90Sr originating from weapons fallout, where 90Sr is deposited in condensed, sub-micrometre particles.However, general problems of incomplete recovery have been recognized, and some labora- tories now routinely use much more vigorous conditions to ensure complete extraction of strontium.8 As uranium oxide is relatively inert to cold HCl (although more reactive in oxidizing conditions) ,I4 it would be expected that complete recovery of 90Sr from fuel particles might not be attained by HC1 extraction alone. Hence, in instances where the fuel particle component was significant, the method could give rise to an underestimate of deposited 90Sr in soils.To test this hypothesis, 90Sr determinations have been carried out by HCl extraction of particle-containing soils from two sources: from near Sellafield (then Windscale), collected in 1956; and from within 15 km of Chernobyl, collected in 1990 and 1991. The efficiency of the HC1 extraction was then assessed by determination of the remaining WSr , following total dissolution of the residues. Experimental Two types of experiment have been carried out. In the first, intended to examine the behaviour of identifiable radioactive particles during extraction, samples of Chernobyl and Wind- scale soil were sequentially extracted with HCl(6 moll-l; two portions), ammonium acetate and finally (for total analysis) a mixture of HF and HN03. The presence of radioactive particles in the samples was demonstrated by autoradiography both before and after the HC1 extractions.In the second experiment, intended to investigate the extent to which 90Sr in particle-containing soils might be under-1102 ANALYST, SEPTEMBER 1993, VOL. 118 estimated in normal laboratory practice, 90Sr in 11 samples of Chernobyl soil was determined by using HC1 extraction, and the results were compared with the total obtained following oxidative alkaline fusion of the residues. Sample Origins and Preparation The Chernobyl soils were taken to a depth of 5 cm, from Bourykovka (May, 1990 and 1991) and from Novo Shepilichi (May, 1991), 15 and 5 km, respectively, from the Chernobyl reactor. Stones and roots were removed, and the soils were dried, crushed and homogenized by gentle grinding.Soils from these locations have previously been characterized both at the Isotope Laboratory, Norway, and the Rise National Laboratory, Denmark, and were found to contain relatively high activities of the refractory fission products (e.g., 144Ce), consistent with the presence of fuel particles.7.15 The Windscale soil was one of a number of grass and topsoil samples collected between 1955 and 1957 from a garden in the village of Seascale, approximately 3 km from the Windscale piles, as part of a contemporary investigation of the emissions of oxidized fuel particles. The piles operated from 1951 to 1957, when both were shut down because of a major fire in one of them.16 Particle releases were first discovered in mid-1955, and were caused by oxidation of incorrectly discharged (metallic uranium) fuel elements in the ducts leading from the air-cooled reactor core to the discharge stack, which housed an ineffective filter system .2717 One such particle (approxi- mately 300 pm in length) was isolated, at the time, from the Seascale garden18 and some of its characteristics have already been reported.7 The Seascale soil samples were stored dry and intact, together with their surface vegetation, until 1991, when they were delivered to the University of Manchester, and thereafter to the Isotope Laboratory in Norway.A number of additional experiments to characterize these materials have now been carried out, and will be reported separately. The Windscale soil sample described in the present paper had been collected in February, 1956, to a depth of approximately 1 cm.In 1991, the vegetation and obvious stones were removed, and the soil (15.2 g) was further dried, crushed, and mixed gently, yielding seven 2 g portions for further investigation. These were first screened by y-ray spectrometry. The only fission product readily detectable was *37Cs, averaging 0.12 k 0.05 Bq g-' in six of the sub-samples. The seventh portion contained (in total) 22.8 Bq of 137Cs, and was assumed to contain one or more fuel particles. This high- activity portion, and a low-activity sample for control purposes, was further examined by autoradiography and then subjected to chemical extraction with HCl. Sequential Extraction Experiments Two 2 g samples of one particular Chernobyl soil (Boury- kovka, 1990) were compared with two 2 g samples of the Windscale soil (i.e., the active sample and the control, as described earlier).Sample preparation, autoradiography and chemical extractions were carried out in Norway, at the Isotope Laboratory. Extracts and residues were then divided, and radiochemical measurements were carried out in dupli- cate, both at the Isotope Laboratory and at the University of Manchester (actinides were also determined at Manchester, and will be reported separately). Measurement differences between the two laboratories for parallel samples did not exceed 10%. As the soils were known to contain small radioactive particles, the loss of even a very small fraction of the sample could potentially affect the results disproportion- ately. Therefore, at all stages in the experiment the 137Cs content of the samples, sub-samples, residues and empty containers was monitored.No losses were detected. For autoradiography, the soils (the initial 2 g portions and the corresponding dried residues after the solution extrac- tions) were examined for the presence of Ply-emitting hot particles using standard X-ray film (Kodak X-OMAT AR-5). The samples were thinly spread on paper, covered with a thin polyethylene membrane, and the X-ray film was placed in close contact on top for 2 weeks exposure. The results are shown in Fig. 1. After the first autoradiographic exposures, the soil samples were treated sequentially with two portions of 6 mol 1-l HCl (20 mi each for 12 h with gentle shaking at 20 "C) and one of 1 mol 1-l ammonium acetate (20 ml for 2 h, intended as a precautionary measure to ensure that none of the extracted 137Cs would be re-adsorbed by soil components). Strontium chloride (20 mg of Sr) was added as a yield monitorlcarrier with each treatment, and on each occasion the residue was washed with water (10 ml), and the washings were added to the appropriate extractant solution.The 137Cs was determined in the initial starting materials, the extracting solutions at each stage, and in the residues. To determine total WSr, the extracted residues were totally dissolved in a 1 + 1 mixture of 60% HF and 16 moll-' HN03, the solutions were evaporated to dryness, and the residual solids were dissolved in 4 moll-' HN03. Comparative Analysis of Chernobyl Soils Strontium-90 was determined in 11 samples of Chernobyl soils (five from Bourkovka and six from Novo Shepilichi, collected in May, 1991) using a standard HCl extraction technique, and the residual 9OSr was then recovered by oxidative alkaline fusion.19,20 Duplicate 1 g portions of each soil were treated with cold 6 mol 1-1 HCI for 24 h, with occasional stirring.The residual solids from the HCl extractions were fused with a mixture of NaOH (41 g), NaKC03 (14 g) and KN03 (0.7 8). The fused mixture was extracted with HN03, and 90Sr was determined in both sets of extracts. Fig. 1 Autoradiographs of Windscale and Chernobyl soils: (a) Windscale soil before chemical extraction; ( b ) Windscale soil after extraction; (c) Chernobyl soil before chemical extraction; and ( d ) Chernobyl soil after extraction.The light patch on the top edge of (a), (c) and ( d ) is due to exposure from exterior lightANALYST, SEPTEMBER 1993, VOL. 118 1103 Radiochemical Measurements At the Isotope Laboratory, WSr was determined by an established laboratory procedure involving extraction of equilibrated 90Y .21 Solutions were evaporated to dryness, the residues were ashed at 400 "C, and the ashes were dissolved in 1 moll-' HCl, with addition of natural yttrium and strontium carriers. Yttrium was isolated by extraction into toluene containing 5% of bis(2-ethylhexyl) hydrogen phosphate (HDEHP), back-extracted into 3 mol 1-1 HN03 and finally determined by Cerenkov counting (Quantilus 1220 low-level liquid scintillation spectrometer; LKB-Wallac, Turku, Fin- land).Chemical yields were determined by complexometric titration. The 137Cs in solids was determined by means of an HPGe (high-purity germanium) detector, and in the extrac- tant solutions using a sodium iodide well (MiniAxi) detector (Canberra Packard Benelux, Tilburg, The Netherlands), cross-calibrated against the HPGe system. At the University of Manchester, strontium (i.e., carrier plus 90Sr) was isolated from 4 mol 1-1 HN03 by chromato- graphy on a strontium-specific solid phase (Sr-SPEC; EI- Chrom Industries, Chicago, IL, USA) and subsequently eluted with water.22 The chemical yield was determined by analysis for total strontium (inductively coupled plasma atomic emission spectrometry; Perkin- Elmer Model 6500, Norwalk, CT, USA), and 90Sr (with equilibrated 9OY) was determined after 3 weeks by liquid scintillation spectrometry [Canberra (Pangbourne, Dorset, UK) Model 2250CAl , using an equilibrated (90Sr-9OY) low-level standard for calibration (National Physical Laboratory, Ref.R715). Caesium-137 was determined by y-ray spectrometry. At the RisG National Laboratory, 90Sr was determined in all extracts using the classical technique of precipitation with fuming HN03, and P-counting (after 3 weeks).19,20 Yields were monitored with 85Sr. Results and Discussion Au toradiography The autoradiographs for the high-activity Windscale soil, before and after HCl extraction, are shown in Fig. l ( a ) and ( 6 ) , respectively. The low activity (control) Windscale soil produced no visible effect on the X-ray film. The analogous autoradiographs for one of the Chernobyl soil samples are shown in Fig.l(c) and (d) (both Chernobyl samples yielded similar results). At the pre-extraction stage, the presence of a considerable number of particles is clearly seen in the Chernobyl soil, while one particle is visible in the active Windscale soil. The resistance of these particles to HC1 extraction is demonstrated by the post-extraction autoradiographs [Fig. l(b) and (d), Windscale and Chernobyl, respectively], although the Windscale particle appears to have broken into two pieces during extraction. Using the particle positions identified by the autoradiograph [Fig. l(b)], the bulk of the residue was physically separated from the two particles. It was found that most of the 137Cs activity was still associated with the particles, not with the bulk soil.Hence, the possibility that 137Cs had been extracted from the particle and resorbed by the soil fraction can be excluded. Sequential HCl Extraction Results for the Windscale soil are summarized in Table 1. The total 137Cs activity of the soil plus particle was 22.8 k 0.5 Bq, whereas that of the control soil was 0.24 f 0.02 Bq (both 2 g). It seems reasonable to infer that, in the more active sample, at least 99% of the 137Cs (and presumably 90Sr) activity was associated with the one particle observed by autoradiography . For this particle, totals of 23 and 25% of the 137Cs and 90Sr, respectively (i. e., within experimental error, the same relative amounts), were extracted. Additionally, the 9OSr : 137Cs ratio (mean 1.7; range 1.5-2.0) does not vary markedly as between the various extracts or between extract and residue.These results suggest strongly that the extraction process results essentially from dissolution of the particle matrix itself. It might also be noted that the 90Sr : 137Cs ratio observed is higher than that assumed (0.9 : 1 .O) for the irradiated fuel that was released.2 The reason for the discrepancy is not clear, but could reflect preferential removal of Cs nuclides (e.g., by volatilization) at some stage in the life of the uranium fuel, perhaps during its oxidation and the formation of particles, which occurred in a hot-air stream over a long period. Possible, but in our view less likely, would be preferential extraction of caesium relative to strontium from the fuel particle after deposition, by weathering processes in the soil.For the analogous sequential extraction of the Chernobyl soil (Table 2), the relative amounts of 137Cs and 90Sr extracted by HC1 were 66 and 2670, respectively. The result for 9OSr, taken together with the demonstration by autoradiography of the presence of extraction-resistant particles, clearly demon- strates the ineffectiveness of HCl extraction for the determina- tion of total 90Sr in this soil. However, the greater extractabil- ity of 137Cs relative to 90Sr, which is also reflected by the Table 1 90Sr and 137Cs activities in sequential extracts and residue from a soil sample collected from near Windscale in February, 1956 Amount Amount WSr : 137Cs Component 137Cs/Bq* (%) WSr/Bq* (%) ratio 1.6rn011-~HC1(12h) 3 . 3 f 0 . 1 14.5 5.1k0.1 14.5 1.5 3. 1 moll-' NH40Ac (1 h) 0.3 f 0.1 1.3 0.5+0.1 1.4 1.7 Total extracted 5 . 2 f 0 . 3 22.8 8.8k0.3 25.0 1.7 Residue (measured) 17.6 f 0.2 77.2 26.4 k 2 75.0 1.5 Total in 2 g sample 22.8 100.0 35.2 100.0 1.54 2. 6m0ll-~HCl(12h) 1.6 f 0.1 7.0 3.2k0.1 9.1 2.0 * Activity f standard deviation (counting statistics). Table 2 WSr and 137Cs activities in sequential extracts and residue from a soil sample collected from near Chernobyl in May, 1990 Amount Component 137Cs/Bq* (%) WSr/Bq* 1. 6moll-' HCl(12h) 84.7 f 0.1 57.8 6.6 Ifr 0.2 2. 6 mol 1-' HCI (12 h) 10.9 Ifr 0.1 7.4 0.7k0.1 3. 1 rnol 1-1 NH40Ac (1 h) 1.0 f 0.3 0.7 0 . 3 f 0 . 1 Total extracted 96.6 f 0.5 65.9 7.6 f 0.4 Residue (measured) 50.0 f 1 34.1 21.4 k 1.5 Total in 2 g sample 146.6 100.0 29.0 Amount 22.7 2.4 1.0 26.2 73.8 100.0 (%> 90Sr : 137Cs ratio 0.078 0.064 0.30 0.079 0.43 0.198 * Activity 1- standard deviation; mean of two 2 g samples.1104 ANALYST, SEPTEMBER 1993, VOL.118 differing 90Sr : 137Cs ratios in the residue and the HCl-extract- able component (0.43 and 0.079, respectively), also suggests that a significant amount of the total 137Cs activity is bound to a matrix other than fuel particles. In relation to the analytical determination of 90Sr in particle- containing soils, the hypothesis outlined in the introduction to this paper has been substantiated by these experiments. In both instances, the HCl extraction method recovered about 20-26% of the total 90Sr present in the soil samples.For the Windscale soil, the incomplete extraction was shown to be due to the presence of a single fuel particle, resistant to extraction by the technique used, and a similar explanation is likely for the low 90Sr recoveries from the Chernobyl soil. Comparative Analysis of Chernobyl Soils In general, it might be expected that the fraction of the total 90Sr extracted from a soil sample would be affected by the fraction of the isotope associated with radioactive particles, the properties of the particles themselves (composition, size/ surface area, degree of post-depositional weathering, etc. ) and by factors related to sample preparation (e.g., drying tempera- ture or amount of sample grinding) and chemical extraction (e.g., temperature, agitation or length of extraction pro- cesses).In the sequential extraction experiments reported above, we deliberately reduced the mechanical factors thought likely to affect particle dissolution (e.g., we avoided fine grinding of the soil before extraction). Hence, while demonstrating that large, intact particles are resistant to chemical attack by HCl, our sequential extraction experi- ments may not be fully representative of routine laboratory soil analysis. In order to evaluate whether HCl extraction underestimates 90Sr in normal practice, we have also carried out determina- tions on 11 particle-containing soil samples from the Cher- nobyl area by the procedure (based on HCl extraction) routinely used at the Ris@ National Laboratory, and which follows a long established and widely used protocol19320 (although we recognize that soil pre-treatment methods for 9% determination vary considerably between laboratories , as indeed do the extraction methods themselves).The results for these soil analyses are presented in Table 3. The fractional W r recovery by HCl extraction (relative to that obtained by alkaline fusion and complete dissolution) ranged from 33 to 85%, with a mean of 54%. It is clear that, for soils containing uranium oxide fuel particles, extraction by cold 6 mol I-' HCI is not a satisfactory technique for the determination of total 90Sr. A significant deposit of condensation-type particles, in addition to fuel particles, in this soil is suggested by the relatively low values for the 90Sr : 137Cs ratios (range 0.27- 0.62), which are below the average ratio (0.71) for the irradiated fuel at the time of the accident.Extraction by HCl and the Alternatives Under conditions in which WSr has been deposited in sub- micrometre particles, and probably in an acid-soluble matrix, as is the case with weapons fallout, HCl extraction has been demonstrably and understandably effective.8.12 However, extraction of trace nuclides from larger particles of a refractory oxide presents a very different problem, as was identified some years ago by Sill and co-workers,9JO in relation to actinide determination. At that time, plutonium in soil from weapons fallout was determined accurately and reliably by an extraction procedure involving HCl or a mixture of HC1 and HN03. Sill9 demonstrated that, for soils contami- nated by 'an accidental release of plutonium' (site not stated), the standard extraction failed to recover all the plutonium, and additionally, if the soil had been strongly heated before extraction, recoveries as low as 530% were obtained.He concluded that treatment with these acids alone 'is grossly inadequate for dissolution of refractory compounds of pluto- nium'. Sill et aZ.10 concluded that only complete dissolution of the sample initially could ensure reliable analysis, and they evolved a method of sample pre-treatment based on a combination of KF and pyrosulfate fusions to meet this problem. Oxides of the lower oxidation states of uranium are only easily soluble in acids under oxidizing conditions.14 In our view, the HCl extraction method is ineffective for soils containing fuel particles, in part because of the lack of oxidizing capability (hence, extraction is enhanced by the use of H202 and/or HN0315).However, in instances in which fuel particles could be involved, even more rigorous oxidizing conditions might be needed. Additionally, thorough grinding of a sample to reduce the particle size (and increase the relative surface area) of the chemically resistant components would clearly assist recovery in instances where an acid- extraction method is to be used (in this context, we are aware of recent work23 in which a Windscale soil, similar to our own, afforded good recovery of 9OSr when extracted with 6 mol 1-1 HCl; however, it is probable that the soil sample was ground to a much finer powder than in our extraction experiments, which could explain the difference in the results obtained).It has been suggested .to us24 that the HCl extraction technique for 90Sr determined in soil is no longer in common usage, and that soil extraction with hot aqua regia (HCl- HN03, 3 + l), which is more likely to achieve complete recovery, is now more commonplace. Traditionally, recom- mended alternatives to acid extraction, for intractable mat- rices, have been alkaline and/or fluoride fusion under oxidizing conditions (as outlined earlier in this paper) .6,7 Table 3 WSr determination (Bq g-') by HCl extraction (and subsequent oxidative alkaline fusion of the residue) for samples of 11 soils containing radioactive particles, collected from near Chernobyl in May, 1991 Yh/Bq g-I in soil Amount in HCl extract Isotope ratio Sample Location* HCl extract Residue ("/.I (WSr : 137Cs) B2-11 B2-11 C2-7 C2-8 C2-9 E2-9 E2-10 E2-11 M-9 M-10 F2-11 BK 1 BK BK BK BK NS NS NS NS NS NS 11.3 f 0.2 6.2 k 0.1 27 f 0.4 23 k 0.3 42 k 0.6 58 k 0.8 49 f 0.7 59 f 0.7 134 f 2.0 132 f 2.0 155 k 2.0 9.9 * 0.1 5.3 rfr 0.1 12.3 k 0.2 18.7 t 0.2 7.4 2 0.1 42 rfr 0.6 66 k 0.8 59 k 0.8 122 k 2.0 270 f 4.0 230 k 3.0 53 54 69 55 85 58 43 50 52 33 40 0.62 0.39 0.30 0.29 0.37 0.43 0.42 0.39 0.27 0.43 0.41 * BK = Bourykovka; NS = Novo Shepilichi (15 and 5 km, respectively, from the Chernobyl reactor site).ANALYST, SEPTEMBER 1993, VOL.118 1105 These methods are all discussed in the recent RADREM (Radioactivity Research and Environment Monitoring Com- mittee) report,g and it does indeed seem likely that many UK laboratories would now not use HC1 extraction routinely for soil analysis.However, we also note that the use of HCl extraction for the determination of WSr in soils, including those which could contain fuel particles, is specifically recommended in the recent IAEA (International Atomic Energy Agency) ‘Guide- book’ for environmental radionuclide determination,13 inten- ded particularly to establish ‘reliable analytical methods to obtain data capable of inter-comparison in the case of radioactive releases’. In the recommended procedure, soil is first dried, weighed, and crushed to pass through a 4 mm mesh sieve. The dry soil (500 g recommended) is then treated with 6 mol 1-1 HCl and allowed to stand, with occasional stirring, for at least 8 h.After filtration, the procedure is repeated and the extracts are combined. This procedure is almost identical with that originally described in 1957 by Bryant et aZ.11 and used (scaled down) by ourselves in the present work. It now seems clear, both from the earlier work and from our own experiments, that HCl extraction is an unreliable method for the extraction of nuclides from soils, at least in instances where fuel particles are likely to be involved. Therefore, we suggest that the IAEA recommendation13 should be viewed with considerable caution. In our view, in instances where oxide fuel particles are likely to be present, only methods based on complete dissolution of the sample should initially be assumed to be reliable, and although methods based on mixed-acid extraction (HC1-HNO3-HF) could be effective, they should be evaluated for the particular circumstances of the analysis. Re-evaluation of Previous Results In view of our conclusions above, it may be necessary to examine the reported experimental methods carefully when evaluating determinations of soil 90Sr reported in connection with the Chernobyl accident, certainly for locations close to the site.Similarly, the determinations of 90Sr in soil near Sellafield in the period following the Windscale pile fire (October, 1957) are likely to have been affected by the presence of uranium oxide particles, as it was established at the time that most of the soil 90Sr identified within 10 km of Sellafield originated from particle emissions that had taken place before the fire.25 It seems to us possible that in both instances the total release of 90Sr will have been under- estimated as a result of the analytical problems we have discussed.We thank Dr. F. Leslie, formerly resident in Seascale, for supplying materials used in this investigation, H. N. Lien of the Isotope Laboratory, Agricultural University of Norway, for carrying out analyses for 90Sr, and Drs. F. R. Livens (University of Manchester) and B. T. Wilkins (UK National Radiological Protection Board), and also the two (anony- mous) referees of this paper, for helpful comments and suggestions. 2 3 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Chamberlain, A. C., Sci. Total. Environ., 1987, 63, 139. Loshchilov, N. A., Kashparov, V.A., Yudin, Ye. B., Protsak, V. P., Zhurba, M. A., and Parshakov, A. E., in The Radiobiological Impact of Hot Beta- Particles from the Cher- nobyl Fallout: Risk Assessment, IAEA, Vienna, 1992, Part I, Bogatov, S. A., and Borovoy, A. A., in The Radiobiological Impact of Hot Beta-Particles from the Chernobyl Fallout: Risk Assessment, IAEA, Vienna, 1992, Part 11, pp. 1-16. Salbu, B., in Proceedings of an International Workshop (Thueren, FRG), eds. von Philipsborn, H., and Steinhausler, F., Bergbau- und Industriemuseums, Thueren, 1988, vol. 16, pp. 83-84. Sandells, F. J., Segal, M. G., and Victorova, N., J. Environ. Radioact., 1993, 18, 5. Salbu, B., Krekling, T., Oughton, D. H., Ostby, G., Kash- parov, V. A., and Day, J. P., Proceedings of the International Symposium on Radioecology. Chemical Speciation-Hot Par- ticles, CEC/IUR Joint Workshop on Hot Particles, Prague, TUR-European Branch, Znojmo, Czechoslovakia, 1992, pp.108-110. Sampling and Measurements of Radionuclides in the Environ- ment, UK Department of the Environment, RADREM Report, HM Stationery Office, London, 1989. Sill, C. W., Health Phys., 1975, 29, 619. Sill, C. W., Hindman, F. D., and Anderson, J. I., Anal. Chem., 1979, 51, 1307. Bryant, F. J., Chamberlain, A. C., Morgan, A., and Spicer, G. S., Radiostrontium Fallout in Environmental Materials in Britain, Report AERE HP/R.2056 (unclassified), AERE, Harwell, UK, 1957. Wilken, R. D., and Diehl, R., Radiochim. Acta, 1987,41, 157. Measurement of Radionuclides in Food and the Environment: a Guidebook, Technical Report series, No. 295, IAEA, Vienna, 1989. Katz, J. J., and Rabinovitch, E., The Chemistry of Uranium, Dover Publications, New York, 1951, p. 322. Oughton, D. H., Salbu, B., Riise, G., Lien, H., 0stby, G., and Noren, A., Analyst, 1992, 117,481. Arnold, L., The Windscale Fire, 2957, Anatomy of a Nuclear Accident, Macmillan Press, London, 1992. Howells, H., Ross, A. E., and Gausden, R., The Release of Oxide from Irradiated Uranium in the Windscale Area Since October 1955, UKAEA Report No. IGO/TM/W036, 1957 (available from the Public Records Office, UK). Leslie, F. R., personal communication, 1990. Harley, J. H., Health and Safery Laboratory Procedures Manual, HASL-300, US Energy Research and Development Administration, New York, 1972. Aarkrog, A., Environmental Studies on Radioecological Sensi- tivity and Variability With Special Emphasis on the Fallout Nuclides WSr and 137Cs, Risd-R-437, Rise National Laboratory, Roskilde, Denmark, 1979. Bjornstad, H. E., Lien, H. N., Yu-Fu, Y., and Salbu, B., J. Radioanal. Nucl. Chem., 1992, 156, 165. Horwitz, E. P., Diety, M. L., and Fisher, D. E., Anal. Chem., 1991, 63, 522. McMahon, A. W., Toole, J., Jones, S. R., and Gray, J., unpublished work. Wilkins, B. T., personal communication, 1992. Bryant, F. J., Spicer, G. S., Chamberlain, A. C., Morgan, A., and Templeton, W. L., Radiostrontium in Soil, Grass, Vege- tables and Milk from Seven Farms in the Windscale Area. Report No. HP/R-2636, AERE, Harwell, UK, 1958. pp. 34-39. References 1 Eisenbud, M., Environmental Radioactivity Academic Press, New York, 3rd edn., 1987, pp. 244-391. Paper 210.51396 Received September 25, I992 Accepted February 11, 1993

ISSN:0003-2654    

DOI:10.1039/AN9931801101

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, SEPTEMBER 1993, VOL. 118 1107 Estimating and Using Sampling Precision Constituents of Soils Michael Thompson and Michael Maguire Department of Chemistry, Birkbeck College, Gordon House, 29 in Surveys of Trace Gordon Square, London, UK WClH OPP Sampling variance and analytical variance have been estimated in a survey of concentrations of trace metals in soils from public gardens in an inner London borough. Robust analysis of variance was used for this purpose and found t o be appropriate. The resulting statistics were used to define criteria that identified unusual measurements for the purpose of checking or further investigation. The statistics were further used to assess the analytical and sampling protocols in respect of their fitness for the task of producing data of appropriate quality, in the light of the variation in the concentrations among the various gardens.Criteria for this latter purpose were also suggested. Keywords: Sampling precision; analytical precision; analysis of variance; robust statistics; soil survey It has become almost a cliche‘ to say that sampling errors are more of a problem than analytical errors, and yet it is seldom that any attempt is made to quantify sampling errors. It is perhaps more seldom that the combined errors resulting from sampling and analysis are formally demonstrated to be of a magnitude appropriate to the task of interpreting the resulting data. This omission is surprising because the requisite information can be obtained by means of a simple experi- ment.1-3 Moreover, the information on sampling and analy- tical errors is essential if reliable and economic decisions are to be made from the data.If the errors are too large they can obscure the information and lead to incorrect decisions. If the errors are very small, it may be that excessive effort (and therefore cost) is being put into the sampling and analytical methodology. This paper describes a hierarchical randomized replicated experiment applied to the study of toxic metals in the soils of urban public gardens. The purpose of the experiment, apart from obtaining preliminary values for the concentrations of the metals, was the estimation of sampling and analytical errors, and their assessment in relation to the actual variation between gardens. This procedure can be seen as a preliminary method of validating sampling and analytical protocols before undertaking a wider survey, an undertaking known as an ‘orientation survey’ in applied geochemistry.4 Although the immediate application of the present paper lies in the environmental field, the experimental design is suitable for a wide range of applications. Nested analysis of variance (ANOVA) is the standard method of treating the data from such experiments.In this paper the use of a relatively new approach is advocated, namely, robust ANOVA.3.5 can be estimated from the results of an experiment with the design shown in Fig. 1, with duplicated sampling and analysis. The computations for the classical ANOVA are shown in Table 1, using the following conventions, where xijh is the kth analysis on the jth sample taken from the ith of 1 sites: x i j = (Xijl + x,)/2 xi = (Zil + &)/2 .z = ci xi11 Estimates (6) of the variances are obtained by equating the expected mean square to the calculated value, i.e., s,”, = MS,, s,”,, = (MS,,, - MS,,)/2 = (MS,ite - MS,,,)/4 Robust ANOVA A classical estimate of a variance a* is based on a sum of squares of the form &(yi - j i ) 2 .Such a sum can be dominated by a small proportion of discrepant values of yi because of the squared terms. This has the unfortunate effect of unduly emphasizing the effects of unusual observations and discount- ing the majority of ‘normal’ observations. This is the antithesis of what is required in orientation surveys where the objective is to define criteria, based on normal observations, that enable the investigator to identify unusual observations in subsequent studies.An alternative approach that achieves the desired end is to use robust methods,6 where the square function is replaced, yielding ZiY(yi - j i ) . The function Y is the square near zero, and the absolute value is outside the limits of +ka. Theoretical Classical ANOVA Consider a single measurement ( x ) , obtained by applying the sampling protocol once to a particular site and analysing the sample once, then x = true value for site + sampling error + analytical error Assuming for the moment that the sources of variation are independent, the variance of x is given by var(x) = os?lte + o,2,, + aa2, where a&, is the variance of the true values of the sites, o:,, is the variance of true values of random samples taken from a site (the sampling variance), and is the variance of analytical measurements performed on random test portions from a sample (the analytical variance).These three variances Analysis 1 Analysis 2 Fig. 1 Design of the hierarchical duplicated experiment executed at 1 sites1108 ANALYST, SEPTEMBER 1993, VOL. 118 ~ ~ ~~~~ ~ _ _ _ _ _ _ _ 6' Table 1 ANOVA table for an experiment with duplicated sampling and analysis at I sites Degrees of Source of variation Sum of squares freedom Mean square Expected mean square Between sites 42& - f ) 2 I- 1 MSsite d n + 2 d a m + 4 d e Between samples 2@jl - f j # I MSsam d n + 2 4 a m Within sampleshetween analyses - Xi2,(q1 - xii2)2 21 MSan 0% 1 2 A common choice is k = 1.5.The application of this method to ANOVA has been discussed in the context of interlaboratory trials,5 and is adapted here for studies of sampling error. The method downweights the influence of outliers in the estima- tion of statistics, and simultaneously corrects for the down- weighting . According to a general principle stated by R O U S S ~ ~ U W , ~ 'outliers can easily be identified by comparing data with a robust fit'. This principle can be applied to the data obtained in orientation surveys and, with caution, to data collected in subsequent surveys. As the purpose is to enable the investiga- tor to identify unusual observations for further study, and not to conduct tests of significance , approximate criteria suffice. Moreover, it must be remembered that no simple exact frequency distributions can be attributed to robust estimates.Potentially anomalous sites are, therefore, a possibility when where .f or MS in bold typeface indicates that the statistic is obtained by the robust method. Unusually discrepant duplicate samples are indicated when IZj - f\/V(Z - 1)MSsite/4Z > 2 \xi1 - Xj21/VMSsam > 2 Possibly spurious duplicate determinations are indicated when lxijl - xi,*//- > 2 Appropriate Magnitudes of Sampling Variance and Analytical Variance Consider the variance of a mean result (X) for a site, based on the collection of rn samples each analysed n times. The value is var(X) = a$te + + a&/n)/rn If we define technical variance as the total variance introduced by the methodology, i.e., d e c h = (a?,, + dn/n)/m then we have var(x) = a;,, + oCch where the magnitude of OLch can be adjusted by altering the values of rn and n.Normally in environmental studies, one of two possibilities is required: to discriminate among background (normal) sites or to distinguish between background and anomalous sites. Both of these requirements are jeopardized if o:ech is relatively large. For example, if (7Lch = o$te, the information in X about variation among sites would be compromised by experimental 'noise'. Accordingly, we should seek to obtain lower values of (7;ech. However, reducing its value to below about 0.1 &, is probably unproductive, as it has little effect on var@), but almost certainly costs more to achieve than a higher value. Hence, an 'ideal' value of O:ech/o$te = 0.3 can be formulated.Consider now the relative sizes of a:,, and a&. Unless the survey material is almost homogeneous rare in soil sampling), it is normally observed that a:,, > o,,. However, there is little benefit to the investigator if >> a:", because a&,/n then makes little contribution to c&h. Again, we suggest an 'ideal' value of a&/n&,, = 0.3. 1 Fig. 2 Illustration of the sam ling protocol applied to a roughly rectangular site, showin the [rst sampling walk (bold line), the duplicate sampling walk bight line) and the points where increments were collected Experimental Sampling Sites Sixteen sites, consisting of grassed recreational spaces, within the London Borough of Lambeth were selected for investiga- tion, so as to provide a reasonably even coverage of the borough.Most were small gardens typically 2000-10000 m2. Some were discrete plots of comparable size at the edge of large parks. While some sites had remained virtually unmodi- fied since urbanization in the middle of the 19th century, others were sites where houses had previously been destroyed by war damage or demolition. The latter sites consisted of rubble covered with a layer of soil, possibly from a distant source. One site had been subject to remediation after an earlier industrial pollution event. All sites were, at the time of sampling, subject to varying degrees of pollution from road traffic exhaust fumes and, in the past, from coal smoke. Sites previously built upon were possibly also contaminated with paint residues.Sampling Protocol Duplicate samples were collected at each site. The first such sample was obtained by aggregating 13 increments, three collected on each leg of an 'M' that was walked across the site. Fig. 2 shows how this was done for a roughly rectangular site. The duplicate sample was obtained by reversing the walk, i.e., with a 'W'. Each increment was collected to a depth of 5 cm with a 25 mm auger. Mechanical Preparation The aggregate samples were dried, broken down by light compression, passed through a 2 mm sieve to remove stones, roots, etc., and reduced to a manageable bulk by dividing with a riffle. The resulting laboratory sample was ground to a fine powder (-80 mesh) and dried at 105 "C for 16 h. Analysis Duplicate test portions (0.250 g) of each sample were weighed into test-tubes and treated with nitric acid (70% m/m, 1.0 ml) at 100-105 "C for 1 h.The resulting mixture was diluted to 25 ml with water. Determination of cadmium, copper, lead and zinc was accomplished by flame atomic absorption spec- trometry under standard conditions. Analysis was conductedANALYST, SEPTEMBER 1993, VOL. 118 1109 Table 2 Analytical data (pg g-1) Site 1 2 3 4 5 6 7 8 Sample 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 Analysis 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 Cadmium 1.90 1.3Q 1.28 1.07 3.23 2.34 1.54 2.55 1.75 1.04 2.41 1.27 2.19 2.45 3.25 2.64 1.07 1.51 2.35 1.55 4.51 7.24 5.24 5.65 2.21 2.86 1.77 1.95 1.09 1.51 0.61 1.02 Copper 68 68 71 64 159 149 137 144 49 47 87 85 67 66 72 71 32 36 51 47 64 69 77 65 116 134 116 122 97 82 58 56 Lead 539 511 522 467 863 825 809 900 539 482 728 722 345 326 544 620 181 195 176 177 27 1 300 327 323 838 815 828 788 524 511 577 634 Zinc Site 295 9 297 314 307 1221 10 1070 508 557 260 11 241 407 419 242 12 246 420 379 154 13 149 294 297 229 14 239 286 268 643 15 67 1 455 462 178 16 177 183 185 Sample 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 Analysis 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 Cadmium 1.29 1.94 1.94 1.89 1.26 0.88 1.71 0.84 1.26 0.63 1.51 1.50 1.05 0.82 1.27 1.68 1.10 1.08 1.30 1.05 2.87 2.56 2.59 2.16 4.41 3.84 3.64 4.41 1.04 0.83 1.06 1.10 Copper 64 65 77 76 51 50 48 47 54 57 82 79 51 71 54 54 47 49 47 45 65 65 49 52 50 77 79 81 80 82 93 ' 93 Lead 406 406 405 386 377 383 34 1 348 51 1 537 692 715 365 382 356 333 486 486 336 329 281 289 33 1 339 474 488 741 739 503 526 630 645 Zinc 269 220 249 250 306 287 685 735 252 248 246 408 242 229 238 148 164 168 204 144 256 558 206 210 287 382 391 401 - 284 290 354 292 directly on the resulting solutions after the suspended matter had settled, or with dilution, as appropriate.The determina- tions for each element were carried out in a random order as a single analytical run. Computing Robust and classical estimates of the three variances were calculated by ANOVA on the unedited data in Table 2, by using a program supplied by Professor B. D. Ripley, Department of Statistics, University of Oxford. Table 3 Statistics obtained by robust and classical ANOVA (pg g-1) Analyte Method R &an 4 a m assite Cd Robust 1.81 0.45 0.21 0.74 Classical 2.05 0.52 0.00 1.24 c u Robust 67.5 3.3 10.5 14.3 Classical 72.8 5.8 11.0 25.7 Pb Robust 489 18.7 86.0 169.5 Classical 496 22.8 88.7 172.0 Zn Robust 310 22.2 107.3 78.9 Classical 341 48.5 147.5 130.4 Results and Discussion Results The raw results of the study are presented in Table 2, and the statistics in Table 3.It is of interest to note that the mean concentrations (in pg g-1) fall well below the levels recom- mended by the Department of the Environment as maxima for land to be used for parks and playing fields,* namely, Cd 15, Cu 1000, Pb 2000, and Zn 1000. The same comment applies to nearly all individual samples also. Applicability of Robust Statistics The results of robust and classical ANOVA can be compared in Table 3.No substantial difference between the respective pairs of estimates is evident in the instance of lead. Zinc, however, displays a different behaviour, with the robust estimates considerably smaller than the classical. It is interest- ing to analyse the differences. ~ For 6,, the classical and robust estimates are 48.5 and 22.2, respectively. The difference is almost entirely accounted for by a few discrepant analytical duplicates (absolute differences of 90, 95, 162, 194 and 302 pg g-1). These discrepancies greatly exceed those for any of the remaining 27 duplicate pairs (Fig. 3) and are readily identified as exceeding the criterion of 63 pg g-1 derived from MSan. No immediate explanation for the discrepancies is apparent, but once they are identified, the results can be checked by re-analysis. Use of a criterion based on classical statistics (137 pg g-l) would fail to identify the lower discrepant duplicates, so the robust value is preferred.For a,,,,, the difference between the estimates can be attributed largely to two occurrences of discrepant duplicate samples, yielding mean absolute differences of 413 and 591 pg g-1. These values are easily visible in Fig. 4 and are identified by exceeding the criterion of 307 pg g-1 derived from MS,,,. In these instances, there is no doubt that the duplicate samples are genuinely different. Large sampling1110 .... . . . . . . . . . I 1 ANALYST, SEPTEMBER 1993, VOL. 118 .. . . 1 I I I . . . . . . . . . . . . 1 I I I 1 I 0 120 240 I 360 480 600 Zinclpg 9-1 Fig. 4 Absolute differences between duplicate sample means 2- is also shown as a vertical bar 1- xil - xi21 - for zinc.The robust criterion for unusually high values ~ 0 100 2001 300 400 500 Zinclpg g-l Fig. 5 Absolute deviations of the site means from the robust grand mean ]Xi - 21 for zinc. The robust criterion for unusually high values v\/0/is also shown as a vertical bar variations are often observed at polluted sites, because, in general, contamination is unlikely to be uniform. This is particularly true for zinc where contamination of soil from corroded galvanized objects would be very localized. In fact, both of the sites that gave rise to discrepant samples have anomalously high average zinc contents. Moreover, one of these samples gave rise to a suspect analytical duplicate, which is thereby, explained (higher analytical variability is expected at higher concentrations).Again, for the orientation survey, the variation within the background sites is of primary concern, so the robust estimate is preferred, as the sites with higher sampling discrepancies are from anomalous sites. Moreover, a criterion based on the classical mean square (428 pg g-1) fails to identify one of the suspect samples. The use of the robust estimate also helps to maintain independence between the sources of variation. At an anomalously high (polluted) site, the sampling and analytical variances are almost certain to be considerably higher than at background sites. The use of the robust estimate removes this type of dependence. For &ite the difference between the robust and the classical estimates is explained by the influence of two sites identified as anomalous by the criterion based on MSsite, with mean concentrations of 829 and 558 pg g-l (Fig.5). As the purpose of an extended survey would be to characterize the variation among the background sites and thereby identify sites that do not conform to the general picture, the use of the robust statistic is justified. The criterion based on classical estimation is higher and less likely to identify anomalous sites. Observations similar to the above apply to the results for cadmium and copper. Suitability of Sampling and Analytical Protocols The robust variance estimates are presented in Table 4, together with the ratios S,”,/S,”,, and 6&h/62te, calculated for single samples at each site and single determinations on each Table 4 Variances and variance ratios obtained by robust ANOVA (basic unit: yg g-1) Analyte 6;” osam - 2 & s,”,/s:a, 6:ech/a:te Cd 0.202 0.044 0,548 4.6 0.45 Cu 10.9 110 204 0.1 0.59 Pb 350 7396 28651 0.05 0.27 Zn 493 11513 6 225 0.04 1.93 sample (n = m = 1).Only the statistics for lead fulfil the previously derived criteria, i.e., the two ratios below the ‘ideal’ value of 0.3. The results for cadmium show that the analysis is unduly variable compared with sampling. This is because the analy- tical method was being used at a concentration of cadmium not greatly above its detection limit. The only means by which the data quality could be significantly improved would be by using a different analytical method.Analytical replication (n > 1) would not help here unless an unacceptable number of replicates were performed. For copper and zinc, the analytical precision is satisfactory, but the sampling precision falls short of requirements. For copper, the situation could be alleviated by duplicate sampling (m = 2, n = 1) or by the equivalent method of preparing the aggregate sample by combining twice the number of incre- ments ’ven in the original protocol. This strategy would make could be remedied only by greatly increasing the number of increments that are aggregated, or perhaps by redefining the nature or size of the sampling targets. 6&/n6sam P = 0.2 and 6&,/6&, = 0.3. For zinc, the situation Conclusions The results of this study show that an orientation survey consisting of a hierarchical replicated experiment followed by robust ANOVA provided valuable information on the magni- tude of sampling and analytical errors and also on the concentrations of the analytes. Knowledge of the robust mean squares allowed unusual measurements to be identified for checking or further investigation more certainly than did their classical counterparts.Moreover, the results provided a direct means of establishing whether the sampling and analytical protocols were satisfactory for the application. In instances where sampling precision was found to be unsatisfac- tory, a remedial strategy was immediately apparent. It is also noteworthy that the sampling precision (in terms of relative standard deviation) was greater for zinc than for the other analytes. This serves to emphasize that the sampling protocol could need to be validated separately for each analyte. References Meisch, A. T., in Computers in the Mineral Industry. Part I , ed. Parks, G. A. , Stanford University Publications in Geological Science, 1964, vol. 9, pp. 156-170. Garrett, R. G., in Statistics and Data Analysis in Geochemical Prospecting, ed. Howarth, R. J . , Elsevier, Amsterdam, 1983, Ramsey, M. H., Thompson, M., and Hale, M., J. Geochem. Explor., 1992,44, 23. Rose, A. W., Hawkes, H. E., and Webb, J. S., Geochemistry in Mineral Exploration, Elsevier, Amsterdam, 1979, pp. 34-35, 32@-329. Analytical Methods Committee, Analyst, 1989, 114, 1699. Huber, P., Robust Statistics, Wiley, New York, 1981. Rousseeuw, P. J., J. Chemometr., 1991, 5 , 1. Problems Arising from the Redevelopment of Gas Works and Similar Sites, Department of the Environment, London, 2nd edn., 1986. Paper 3101533E Received March 17, 1993 Accepted April 21, 1993 pp. 83-107.

ISSN:0003-2654    

DOI:10.1039/AN9931801107

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, SEPTEMBER 1993, VOL. 118 1111 Spectroscopic Probes for Hydrogen Bonding, Extraction Impregnation and Reaction in Supercritical Fluids" Andrew 1. Cooper, Steven M. Howdle,t Catherine Hughes, Margaret Jobling, Sergei G. Kazarian,* Martyn Poliakofft and Lindsey A. Shepherd Department of Chemistry, University of Nottingham, Nottingham, UK NG7 2RD Keith P. Johnston Department of Chemical Engineering, University of Texas, Austin, TX 78712, USA Spectroscopy is used for monitoring a number of processes relevant to solution, extraction and impregnation in supercritical C02 (scC02). Examples include: a combined infrared (IR) and ultraviolet study of the interaction between para-hydroquinone (HQ) and tributyl phosphate in scC02, which reveals hydrogen bonding, detected by the characteristicv(0-H) IR bands; IR measurement of the solubility of c ~ M n ( C 0 ) ~ (Cp = q5-C5H5) in scC02 as a function of temperature and pressure; an investigation of the uniformity of supercritical impregnation of CpMn(C0)3 into 4 mm diameter pellets of polyethylene (PE) using Fourier- transform infrared (FTIR) microscopy and FTIR depth profiling by photoacoustic detection; and an IR study of the photochemical reaction of c ~ M n ( C 0 ) ~ with N2 with PE film.Keywords: Supercritical fluid; hydrogen bonding; impregnation; polyethylene; photochemical reaction The role of supercritical fluids in analytical chemistry is the focus of increasing interest not only because of the inherent potential of supercritical fluidsl-3 themselves but also because they represent an environmentally more acceptable alterna- tive to many of the solvents currently in use in the analytical laboratory.Most of the work in this area has concentrated, quite rightly, on applications of supercritical fluids, particu- larly in the areas of extraction and use of modifiers to enhance the solubility of individual solutes.2 By contrast, there has been relatively little development of spectroscopic techniques to probe and monitor these processes in situ. It is the purpose of this paper to describe new applications of infrared (IR) spectroscopy to a range of problems associated with the use of supercritical fluids in an analytical context. These applications have largely evolved from the study of chemical reactions in supercritical fluids at Nottingham ,4-8 which required, inter a h , the development of versatile IR and ultraviolet (UV) cells for monitoring the progress of the reactions.9-11 Our results are divided into three sections: (i) a combined IR and UV study to establish the role of hydrogen bonding in the action of tributyl phosphate (TBP) as a modifier for the solubilization of hydroquinone in super- critical C02 (scC02); (ii) the use of IR techniques for monitoring the impregnation and extraction of organometallic compounds from polyethylene (PE); and (iii) a study of photochemical reactions of organometallics within polymers to explore the potential of these compounds for in situ derivatization and spectroscopic labelling of polymer addi- tives.Experimental Spectroscopy The UV spectra were obtained on a Perkin-Elmer Lambda 5 spectrometer with Epson data station.Transmission IR spectra were recorded on a Nicolet Model 730 interferometer and 680D data system (16K data collection, 32K transform * Based on a lecture presented at the Current and Future Applications of Supercritical Fluid Extraction meeting of the Western Region of the Analytical Division of The Royal Society of Chemistry, Cardiff, UK, October 2, 1992. t To whom correspondence should be addressed. * Permanent address: Institute of Spectroscopy, Russian Academy of Sciences, 142092 Troitzk, Moscow Region, Russia. points, 2 cm-1 resolution). Fourier-transform infrared ( R I R ) microscopy was carried out at 8 cm-1 resolution with a NicPlan IR microscope with SpectraTech automatic trans- lation stage, using a Nicolet Model 730 interferometer.Photoacoustic measurements were made at 8 cm-1 on a Bio-Rad Model 896 step-scan FTIR interferometer equipped with a demodulator accessory for phase modulation experi- ments and fitted with an MTEC photoacoustic detector. Materials The following reagents were all used without further purifica- tion: c ~ M n ( C 0 ) ~ (Cp = q5-C5H5) (Strem), TBP (BDH), para-hydroquinone (HQ; BDH), C02 (Air Products SFC grade), N2 (Air Products) and low density PE pellets (BP Research) were used without further purification. The PE film was formed from powdered, low-density PE (Aldrich) using a constant thickness melt press Specac (Model 15620). 12 Super- critical impregnation was carried out as described in detail elsewhere ,11712 by immersing PE pellets overnight in a near-saturated solution of CpMn(C0)3 in scC02 at about 40 "C and 2000 psi pressure (145 psi = 1 MPa) with a modified Nupro TF Series in-line filter, 5 ym pore size, as the pressure vessel.12 Pellets were sectioned with a Leitz sledge microtome.Results and Discussion Hydrogen Bonding Hydrogen bonding has been intensively studied for many years and the process is well understood in both gas and condensed phases. 13 Supercritical fluids offer the unique opportunity to observe the effect on hydrogen bonding of varying the density of the medium without altering the concentrations of either proton donor or acceptor.14.15 More importantly, hydrogen bonding appears to be a major factor in the action of many, if not the majority, of the modifiers currently used to enhance the solubility of particular com- ponents in supercritical extraction.A better understanding of hydrogen bonding in supercritical fluids should, therefore , lead eventually to a more rational approach to the design and choice of modifiers for individual applications. There have been a number of studies of supercritical hydrogen bonding,14Js particularly by Yee et aZ.14 The usual approach has been to use IR spectroscopy to detect the characteristic shift in the v(0-H) vibration of the proton1112 ANALYST, SEPTEMBER 1993, VOL. 118 2.9 2.4 Q) 2 1.9 e 8 2 1.4 0.9 0.4 _. . 195 215 235 255 275 295 315 335 Wavelengthlnm f(O-H---O) HQ 3400 3200 3000 2800 Wavenumbedcm-1 Fig. 1 (a) UV and ( b ) IR absorption spectra showing the effect of increasing amounts of TBP on the solubility of HQ in scC02.The IR spectra cover the v(C-H) region of TBP itself and the ~ ( 0 - H ) bands of the hydrogen-bonded HQ-TPB complex. Each trace (UV or IR) was recorded with a separate solution with a different concentration of TBP but the IR and UV spectra for the same concentration of TBP were recorded from the same solution in the same cell (2 ml volume and optical pathlength 5 mm). In each case, a measured amount of TBP was syringed into the cell, containing excess solid HQ. The cell was then pressurized with scC02 to 3700 psi (c 25 MPa). The traces in the UV spectra (a) correspond to additions of 4, 14 and 24 pl of TBP and those in the IR spectra (b) to 0 , 4 , 14,24 and 34 pl of TBP donor, which occurs on formation of a hydrogen bond.One problem is that, in scC02, the absorptions of the scC02 itself obscure the ~ ( 0 - H ) bands of the free proton donor or, with deuteriated donors, the ~ ( 0 - D ) of the D-bonded complex.14 Clearly, this limitation can be overcome by switching to fluids that do not absorb in this region of the spectrum ( e . g . , C2H614 or SF615*16) but this option is not open if the aim is to study bonding in scC02 under realistic analytical conditions. Here, we illustrate a different approach, the combined use of UV and IR spectroscopy. Tributyl phosphate is well known for its use in a wide range of extraction processes in conventional solvents and for its ability to form hydrogen bonds.17 Recently, Lemert and Johnston18 reported how TBP could be used as a far more effective modifier than CH30H in scCO2 to increase the solubility of HQ by over two orders of magnitude.para- Hydroquinone has a higher melting point and lower vapour pressure than the ortho-isomer; the consequence of intermol- ecular hydrogen bonding. It was, therefore, postulated18 that the effect of TBP as a modifier is to hydrogen bond to the OH groups of HQ. This proposition has now been tested spectro- scopically. The strategy has been to use UV absorption to detect the total amount of HQ in solution and IR spectroscopy not only to establish the amount of TBP in solution but also to detect the presence of hydrogen bonding via the shifted ~ ( 0 - H ) bands. O=P /OBU -0Bu OBu H O G O H HQ \ TBP "0-0-H ---O=P(OBu)3 1 Fig. 1 shows the IR and UV spectra of a series of solutions in scC02 containing increasing amounts of TBP and in each case saturated with HQ.The UV spectra, [Fig. l(a)], clearly confirm that the concentration of HQ in scC02 increases with an increasing concentration of TBP. At the same time the IR spectra, [Fig. l(b)] indicate increasing concentrations of hydrogen-bonded species in solution, thus supporting the postulation that, in this case, the role of TBP involves hydrogen bonding. Unfortunately, IR is not a precise enough technique to distinguish easily between the bands caused by hydrogen bonding to one or to both of the OH groups in HQ, i.e., structures 1 and 2, or indeed to identify species containing more than one molecule of HQ. However, mathematical modelling18 of the effects of TBP on the solubility of HQ favoured the formation of an HQS(TBP)~ adduct (2).Cur- rently, we are applying similar techniques to simpler systems to quantify the role of the supercritical solvent in hydrogen bonding,16 using (CF3)3COH as the proton donor; (CF3)3COH has the advantage that it does not self-associate to any significant extent, thus simplifying the systems even further. Impregnation of Polymers In a supercritical extraction experiment, it is usually much easier to measure the amount of material, extracted into the fluid, which is initially 'clean', than it is to measure the amount of guest material remaining in the host matrix. Impregnation is the inverse of extraction and the converse is true of the ease of measurement. In impregnation experiments, it is much easier to measure spectroscopically how much material has pene- trated the host matrix because, at the start of the experiment, the host matrix does not normally contain any of the guest material to be impregnated. Transition metal carbonyl compounds are particularly suited to impregnation experiments.They are relatively volatile, strongly hydrophobic compounds with very intense IR absorptions, due to v(C-0) vibrations, the wavenumbers of which are highly sensitive to the environment.11 Thus it is possible to distinguish spectroscopically between a compound dissolved in scC02 and the same compound impregnated into PE. The way in which this property can be exploited for monitoring the impregnation and extraction of CpMn( CO), in thin 4 0 0 pm PE film has recently been described.11 In this paper, the work is concentrated on investigating more bulky samples, specifically, near spherical pellets about 4 mm in diameter.Such pellets are of considerable relevance to current models of supercritical extraction, including the Leeds 'Hot- Ball' model. 19320 Briefly, the impregnation experimentllJ2 involves immers- ing the polymer pellet in a solution of c ~ M n ( C 0 ) ~ in scC02. Impregnation is allowed to occur, the pressure is vented and the pellet removed. This study has had two aims: (i) to establish the uniformity of the impregnation of the pellets; and (ii) to investigate the solid residue left on the surface of the polymer, when the supercritical solution is depressurized. There have been relatively few studies21 on the solubility of carbonyl compounds in scC02 and no data were available for c ~ M n ( C 0 ) ~ .Therefore, a brief study of solubility as a function of temperature and pressure using the circulating system illustrated in Fig. 2 was carried out, by monitoring the concentration of dissolved c ~ M n ( C 0 ) ~ by FTIR. The results are summarized in Fig. 3. Like other solutes,' the solubility of CpMn(C0)3 in scC02 increases sharply with pressure and decreases with temperature at a constant pressure under the conditions used. Thus, although impregna- tion would be expected to proceed more effectively at higher temperatures, the concentration of CpMn(CO)3 in super- critical solution will be lower if the pressure is not increased. In the present experiments, therefore, a temperature close to the critical point of C02 was used.ANALYST, SEPTEMBER 1993, VOL.118 6 5 - 4 - 0 e B 3 - 2 0: 2 - 1 - 1113 (a) Once the pellet is impregnated, the strategy has been to microtome thin sections from the pellet and then to scan the section using an IR microscope with a 100 pm spot-size to measure the distribution of the impregnated carbonyl com- pound. Fig. 4 shows the result of one such scan across the diameter of a section, which indicates that the impregnation is remarkably uniform. Although, the concentration of scco, Fig. 2 Schematic diagram of the system used for monitoring the solubility of CpMn(C0)3 in scC02. The components are marked as follows; P, Micropump Model 180SC ultrahigh pressure circulating pump; IR, cell of 1 mm pathlength for IR detection of CpMn CO ; and R, Nupro in-line filter to act as a reservoir for solid CpMn[CO{i.All components, except the cell, were placed in a heated box; the cell itself and connecting pi ework were heated with heating tape. Additional scCO2 was afded as appropriate from a Lee Scientific Model 501 syringe pump. The whole system was allowed to equilibrate for 30-40 min before each measurement Pressure/psi 2.0 1.8 1.6 1.4 1.2 1 .o 20 30 40 50 60 70 Tern peratu rePC Fig. 3 IR spectra obtained with the apparatus illustrated in Fig. 2, showing the qualitative effects of (a) pressure and (b) temperature on the solubility of CpMn(C0)3 in scC02. (a) Effect of pressure at 32 "C. The ordinate scale refers to the absorbance of the al v(C-0) band of CpMn(C0)3 and the maximum absorbance value, about 6, corre- sponds to an approximate concentration of 2 x mol 1-l.(b) Effect of temperature at a constant pressure of 2000 psi (e 13.8 MPa). Note that in ( a ) , the data are presented as if IR absorbance can be measured accurately to a value of >6. In reality, these high absorbance values were obtained by a two stage process: (i) while the v(C-0) bands were in the absorbance range 2-3, the absorbance values were measured for the first overtone and combination bands about 4000 cm-1, which are inherently much weaker than the fundamental vibrations, and their intensities relative to the fundamen- tal bands were established; (ii) when the intensity of the v(C-0) bands exceeded an absorbance of 3, the absorbance values of the overtones could be used to calculate the 'absorbance' of the fundamental bands c ~ M n ( C 0 ) ~ is higher close to the outside of the pellet, overall it varies by less than 30%. Two dimensional scans, such as that illustrated in Fig.5 , provide very similar results and the high symmetry of the contours in Fig. 6 suggest that sectioning of the pellet with the microtome causes minimal distortion of the pellet and has little effect on the distribution of c ~ M n ( C 0 ) ~ . As the overall procedure (impregnation, sectioning, spec- troscopy) was relatively drawn out, these results do not show the distribution of c ~ M n ( C 0 ) ~ within the pellet at the moment immediately following the end of impregnation. Recent experiments in our laboratory22 have suggested that molecules the size of CpMn(C0)3 are relatively mobile, at least over short distances, in PE at room temperature over a period of minutes.Nevertheless, the fact that the present experiments revealed a slightly higher concentration of C ~ M n ( c 0 ) ~ close to the outside of the pellet suggests that bulk diffusion of c ~ M n ( C 0 ) ~ within the PE must be slow on the timescale of the experiment (i.e., over a period of days). Experiments with finely powdered KBr have shown" that c ~ M n ( C 0 ) ~ deposited from scCO2 solution onto the surface has an IR spectrum with relatively sharp v(C-0) bands, a spectrum quite distinct from the very broad bands normally observed with bulk solid CPM~(CO)~, possibly due to the amorphous nature of the deposited material.Although the IR spectrum of this deposited CpMn( CO), is also significantly different from that of the compound impregnated into PE, it is a challenging task to use IR spectroscopy for the characteriza- tion of the deposits of CpMn(C0)3 on the surface of the 4 mm PE pellets. Direct transmission spectroscopy is not practic- 2100 2000 1900 Wave n u m be r/cm - 1 Fig. 4 Results of the FTIR microscopic investigation (100 pm spot size) to establish the distribution of CpMn(COh, impregnated into a PE pellet. (a) Schematic view of the pellet showing a section (about 50 pm thick) and the path scanned across it by the FTIR microscope. (b) Computer-generated display of the distribution of CpMn(C0h across the pellet. The ordinate axis shows the ratio of the absorbance the al band of CpMn(C0)3 to the absorbance of a weak band of PE itself (2017 cm-I).By using the ratio of bands rather than the absorbance, any effects that might be caused b non-uniformity in the thickness of the section can be eliminated. (cf A spectrum showing the v(C-0) bands of impregnated CpMn(C0)3 with the al mode arrowed and absorptions of PE removed1114 1.8 Fig. 5 Two-dimensional FTIR microscope scan of a microtomed section obtained by exactly the same method as that described for Fig. 4 3.0 E E R 0 1.8 xlm m 0 Fig. 6 FTIR contour plot corresponding to the data illustrated in a perspective view in Fig. 5. The contours give the values of the absorbance ratio (as defined in Fig. 4), which increase in the direction of the arrow and are plotted from (A) 6.3 to (G) 8.1, at intervals of 0.3.Note in particular, that the contours are essentially circular. If the microtome were distorting the pellet severely during sectioning, one would expect a corresponding distortion of the contours able, because the thickness of the surface layer is undoubtedly small compared with the dimensions of the pellet. Equally, the layer is thin compared with the diameter of the spot viewed through the IR microscope. Although diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) has been highly successful in making such measurements on impreg- nated PE powder,” we have found DRIFT’S difficult to use with these pellets because the surface gives rise to sufficient specular reflection to degrade the spectrum. The solution to these problems has been to use FTIR with photoacoustic detection, because this technique has a rela- tively shallow penetration depth and, furthermore, offers the possibility of depth profiling.23-28 Photoacoustic detectors rely on absorption of IR radiation by the sample to heat a carrier gas, causing a pressure rise which is detected with a sensitive microphone.Depth profiling of a sample can be achieved in two ways, by varying the scan velocity or by so-called ‘step’ scanning. ANALYST. SEPTEMBER 993, VQL. 118 2060 1920 Wavenumber/cm-l Fig. 7 FTIR photoacoustic depth profiling of an intact impregnated PE pellet by means of interferometer mirror velocity. In this case, mirror velocity is defined by the frequency at which the data points are recorded.Spectrum A was obtained with the highest frequency, 20 kHz, corresponding to the shallowest depth of sampling. The other spectra were recorded at: B, 800 Hz; C, 200 Hz; and D, 50 Hz, corresponding to increasing depths of penetration. The bands are labelled as follows: S, surface deposited solid CpMn(C0)3; M, molecular CpMn(C0)3, impregnated into the bulk of the solid PE. Note that this particular sample was washed with heptane prior to recording the spectrum in an attempt to reduce the thickness of the surface layer. Given the restricted wavenumber region of the spectra, the ‘photoacoustic response’ of the ordinate scale of the spectra can be reasonably equated to absorbance. Altering the mirror velocity of the FTIR interferometer alters the modulation frequency of the IR radiation incident on the sample.In general, the more rapid the modulation, the shallower the depth of sample from which the photoacoustic signal can originate; fast mirror velocities yield information only from the surface region, whereas lower’velocities provide the sum of the spectra from the surface and from the layers beneath it.23-25 Fig. 7 shows a set of photoacoustic spectra of an impregnated pellet , recorded with different mirror velo- cities. These spectra confirm the existence of the surface layer but not its thickness. There is a clear transition from the bands of solid CPM~(CO)~, arrowed, to the superimposed spectra of solid and impregnated c ~ M n ( C 0 ) ~ as the mirror velocity is reduced. Step-scanning is a relatively new feature in commercial FTIR instrumentation.2c28 Although the detailed mechanics of the process are intricate,2628 the principle of operation is straightforward.In a conventional interferometer, the IR signal is not measured continuously but at regularly spaced points along the path of the moving mirror, points determined by the calibrating Heme laser. In a step-scan instrument, the moving mirror appears to spend a relatively long time stationary at one measurement position and then jumps almost instan- taneously to the next position.26-28 This behaviour permits additional modulation of the IR beam at a frequency that is fast compared with the time spent by the mirror at each measurement point. When this double modulation is applied to photoacoustic experiments, the detector can be linked to a phase-sensitive amplifier and, as described elsewhere ,2628 varying the phase of detection relative to the phase of modulation allows spectra to be obtained from different depths within the sample, the larger the phase angle the greater the depth. Fig.8 illustrates the effect of varying the phase angle in phase modulated photoacoustic spectra of a PE pellet impregnated with c ~ M n ( C 0 ) ~ . The spectra show a good transition from the spectrum of pure solid CpMn(C0)3 to that of pure impregnated CPM~(CO)~, in a manner that the spectra in Fig. 7 do not. However, the technique does not haveANALYST, SEPTEMBER 1993, VOL. 118 1115 an inherent scale of depth so, again, the precise thickness of the surface layer (probably only a few pm) cannot be established from these spectra. It is therefore, clear that step-scan photoacoustic measurements of this type have considerable promise for probing such samples but without extensive calibration the results are only semi-quantitative.Photochemical Reactions Within the Polymer Currently, there is considerable interest in the use of supercritical fluid extraction (SFE) for identification and quantification of polymer additives.2.29 Unfortunately, some classes of additives, e.g., those with amine functions, are often almost insoluble in scC02 because of reaction with the COz itself. * However, transition metal carbonyl complexes, e.g., CPM~(CO)~, undergo facile photochemical reactions with many such compounds.30 Work is currently underway to explore the feasibility of using carbonyl complexes for reactive extraction of additives, exploiting the carbonyl not only to t v) c 0 n 2 8 0 3 .- 4- 0 .c L 4- 'J 171" 0" 1 u 9" 1 18" B B 1 2060 1920 2060 1920 vlcm-1 Fig.8 FTIR photoacoustic depth profiling of an intact impregnated PE pellet using step-scan phase modulation. Spectra were recorded as the phase angle was varied from 0" to 180" in steps of 9" and a representative set of spectra are shown. From 45" to about 90" the bands in the spectra are those of solid CpMn(C0)3 and from 90" the arrowed bands of CpMn(C0)3 impregnated into the bulk of the PE gradually increase so that by 18" all trace of the surface bands have disappeared. In principle, the surface species might be expected to appear at a phase angle of 0 O but the naoture of the equipment appears to generate a phase shift of about 45 .As in Fig. 7, 'photoacoustic response' can be reasonably equated to absorbance sequester the reactive functional group of the additive but also to provide an excellent spectroscopic label. Carbonyl com- pounds have intense absorptions in both IR and UV and, therefore, should greatly increase the sensitivity of spectro- scopic detection of the complexed additives. For example, (C6H3Me3)Cr(C0)3 has an injected minimum detectable quantity of only 20 pg for capillary supercritical fluid chromatography-FTIR .31 As the first step in this investigation, the photochemical reactions of carbonyl compounds in pure PE film were examined. Fig. 9 shows spectra obtained during and after the UV irradiation of CPM~(CO)~, previously impregnated into low-density PE film, under a high pressure of N2 gas, as the added reactant.It can be seen that there are in fact two products, not only the expected dinitrogen complex32 C P M ~ ( C O ) ~ N ~ but also a complex formed by coordination of the c ~ M n ( C 0 ) ~ moiety to the pendant olefinic C=C bonds, which occur at random intervals down the polymer chain.2>33 This olefinic product can also be formed in the absence of N2 and appears not to be easily extractable from the polymer by subsequent SFE with scCO2. There are two reasons why this experiment is of relevance to reactive extraction. Firstly, it demonstrates that there is sufficient mobility within the polymer matrix for photochemical reactions of CpMn(C0)3 to occur.Secondly, it shows that, although reaction between carbonyl and polymer would clearly consume some of the carbonyl compound, such products will be unextractable so may well not interfere with the overall SFE process. Conclusions The experiments described in this paper have shown the IR and, to a lesser extent, UV spectroscopy can provide valuable in situ monitoring of processes of importance to the exploita- tion of supercritical fluids in analytical chemistry. Transition metal carbonyl complexes, a range of compounds not nor- mally associated with this area of chemistry, have the 4.4 3.3 al c m + 2.2 s 2 B B (a) 1 .I 0 2065 1983 1901 Wavenumberlcm-1 Fig. 9 IR spectra illustrating the photochemical reaction of CpMn(C0)3 with N2 in low density PE film, 500 pm thickness.The film was first impregnated with CpMn(C0)3 at 3000 psi (c 20.7 MPa). The C02 was vented, excess solid CpMn(C0)3 removed and the cell refilled with N2 at 3000 psi. (a) Spectra recorded over a 60 min period of UV irradiation, showing the decay of the bands, B, of im regnated CpMn CO and the growth of bands N, of CpMn(CO)2(N2fand P, of CpMn[CO]2(q2-polymer)1116 ANALYST, SEPTEMBER 1993, VOL. 118 spectroscopic properties needed for probing the impregnation and extraction of polymers. Supercritical fluid extraction is still a largely empirical technique. We believe that, in the near future, spectroscopic investigations will provide a new approach for studying supercritical extraction, an approach which will complement the methods in use today and will help to reach a better understanding of SFE.We thank SERC (Grant No. GR/G0823), the Royal Society, the Nuffield Foundation, Nicolet Instruments Ltd. and BP International Ltd. for support. We are particularly grateful to Dr. S. F. Parker and Dr. C . Baker for their help with the FTIR microscopy and Dr. A. Grady for his assistance with the photoacoustic measurements. We thank Dr. I. G. Anderson, J. A. Banister, Dr. G. Davidson, J. G. Gamble, Dr. T. J. Jenkins, Dr. M. A. Healy, T. Lynch, K. Stanley and Professor J. J. Turner for their help and advice. 1 2 3 4 5 6 7 8 9 10 11 12 References McHugh, M. A., and Krukonis, V. J., Supercritical Fluid Extraction, Butterworth, Boston, 1986. Analytical Supercritical Chromatography and Extraction, eds. Lee, M. L., and Markides, K.E., Chromatography Conferences, Provo, UT, 1990. Vigdergauz, M. S., Lobachev, A. L., Lobacheva, I. V., and Platonov, I. A., Russian Chem. Rev., 1992, 61,267. Howdle, S. M., and Poliakoff, M., J. Chem. SOC. Chem. Commun., 1989,1099. Howdle, S . M., Grebenik, P., Perutz, R. N., and Poliakoff, M., J. Chem. SOC. Chem. Commun., 1989, 1517. Howdle, S . M., Poliakoff, M., and Healy, M. A., J. Am. Chem. SOC., 1990, 112, 4804. Jobling, M., Howdle, S. M., Healy, M. A., and Poliakoff, M., J. Chem. SOC., Chem. Commun., 1990, 1278. Howdle, S. M., Jobling, M., George, M. W., and Poliakoff, M., Proceedings of the Second International Symposium on Super- critical Fluids (Boston), ed. McHugh, M. A., Johns Hopkins University, MD, 1991, p. 189. Poliakoff, M., Howdle, S. M., Healy, M.A., and Whalley, J. M., Proceedings of the International Symposium on Super- critical Fluids, ed. Perrut, M., SocietC Franc. de Chimie, 1988, p. 967. Howdle, S. M., Jobling, M., and Poliakoff, M., Supercritical Fluid Technology; Theoretical and Applied Approaches in Analytical Chemistry, eds. Bright, F. V., and McNally, M. E., ACS Symposium Series, 1992, 488, 121. Cooper, A. I . , Howdle, S. M., and Ramsay, J. M., J. Polymer Sci. Polymer Phys., in the press. Jobling, M., Ph.D. Thesis, University of Nottingham, UK, 1992. 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 The Hydrogen Bond-Recent Developments in Theory and Experiment, eds. Schuster, P., Zundel, G., and Sandorfy, C., North Holland, Amsterdam, 1976. Yee, G. G., Fulton, J. L., and Smith, R.D., J. Phys. Chem., 1992,96, 6172, and references therein. Gupta, R. B., Combes, J. E., and Johnston, K. P., J. Phys. Chem., 1993,97,707. Kazarian, S. G., Gupta, R. B., Johnston, K. P., and Poliakoff, M., unpublished work. Ferraro, J. R., and Peppard, D. F., J. Phys. Chem., 1961, 65, 539. Lemert, R. M., and Johnston, K. P., Ind. Eng. Chem. Res., 1991,30, 1222. Bartle, K. D., Boddington, T., Clifford, A. A., Cotton, N. J., and Dowle, C. J., Anal. Chem., 1991, 63,2371. Bartle, K. D., Clifford, A. A., and Cotton, N. J., Analyst, submitted for publication. Warzinski, R. P., and Holder, G. D., Proceedings of the Second International Symposium on Supercritical Fluids (Boston), ed. McHugh, M. A., Johns Hopkins University, MD, 1991, p. 161. Cooper, A. I., Kazarian, S. G., and Poliakoff, M., Chem. Phys. Lett., 1993, 206, 175. Graham, J. A., Grim, W. M., 111, and Fateley, W. G., in Fourier Transform Infrared Spectroscopy: Industrial and Labor- atory Chemical Analysis, eds. Ferraro, R., and Krishnan, K., Academic Press, New York. vol. 4. 1990. Urban, M. W., Polym. Mater. Sci. Eng., 1991, 64, 31. Yang, C. Q., Appl. Spectrosc., 1991,45, 102. Crocombe, R. A., Curbelo, R., Leonardi, J., and Johnson, D. B., in Eighth International Conference on Fourier Transform Spectroscopy, eds. Heise, H. M., Korte, E. H., and Seisler, H. W., Proc. SPIE Int. SOC. Opt. Eng., 1992, 1575, 189. Crocombe, R. A., Compton, S. V., and Leonardi, J., in Eighth International Conference on Fourier Transform Spectroscopy, eds. Heise, H. M., Korte, E. H., and Seisler, H. W., Proc. SPIE Int. SOC. Opt. Eng., 1992, 1575, 193. Lerner, B., Nicolet FTIR Technical Note, TN-9253, Nicolet Instruments, Madison, WI, 1992. Ashraf-Khorassani, M., Boyer, D. S., Cross, K., Levy, J. M., and Houck, R. K., Proceedings of the Second International Symposium on Supercritical Fluids (Boston), ed. McHugh, M. A., Johns Hopkins University, 1991, MD, p. 219. Geoffroy, G. L., and Wrighton, M. S., Organometallic Photo- chemistry, Academic Press, New York, 1979. Jenkins, T. J., Kaplan, M., Davidson, G., Healy, M. A., and Poliakoff, M., J. Chromatogr., 1992, 626, 53. Sellmann, D., Angew. Chem. Int. Ed. Engl., 1971, 10,919. Cooper, A. I., Clark, M., Jobling, M., Howdle, S. M., and Poliakoff, M., unpublished work. Paper 31012711 Received March 4, 1993 Accepted May 5, 1993

ISSN:0003-2654    

DOI:10.1039/AN9931801111

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, SEPTEMBER 1993, VOL. 118 1117 Determination of Derivatized Urea Herbicides in Water by Solid-phase Extraction, Methylation and Gas Chromatography With a Nitrogen-Phosphorus Detector Steven Scott Essex Water Co., Trace Organics Laboratory, South tianning field, Chelms ford, Essex, UK Four urea herbicides, isoproturon, chlorotoluron, linuron and diuron, were determined by gas chromato- graphy (GC) with a nitrogen-phosphorus detector (NPD) after derivatization, with detection limits of 0.035, 0.039, 0.041 and 0.036 pg 1-1, respectively. The concentrations of all analytes were linear over the range 0.1-8.0 pg 1-1, with recoveries in excess of 75% from spiked potable waters. In their standard, underivatized form the herbicides were found to be thermally unstable on passage through a GC column.After derivatization, by methylation using iodomethane and a strong base, the resulting compounds were found to be stable at elevated temperatures, and so could be determined by GC. The derivatized herbicides were also analysed by GC-mass spectrometry, in order to elucidate the structures of the derivatized compounds. Each compound yielded a different product with a different retention time. The reaction was of the type typical of nucleophilic displacement, with the methyl group attacking the nitrogen of the amide group, forming a stable tertiary amide and hydrogen iodide gas. This method was found to be more selective than the Standing Committee of Analysts' method owing to the nature of the analysis. Firstly, GC, compared with high- performance liquid chromatography, offers better resolution.There are many ultraviolet absorbers in water which can be detected by the standard method, but use of a specific detector, such as an NPD, offers better selectivity. The method was also applied to other urea herbicides, including monuron, methabenzthiazuron and tebuthiuron, which were also successfully determined, although no quantitative data have been obtained. Keywords: Urea herbicide; gas chromatography with a nitrogen-phosphorus detector; meth ylation; water; solid-phase extraction As stated in Guidance on Safeguarding the Quality of Public Water Supplies ,1 urea herbicides2 are persistent in water and most damaging to the aquatic environment3 and are likely to reach water supplies. The maximum values for isoproturon and diuron within the Essex Water Company boundary of supply4 were 0.39 and 0.14 pg 1-1, found in potable waters in weeks 4 and 35 of 1992, respectively. Raw water samples reached 1.6 pg 1-1 for isoproturon, 0.36 pg 1-1 for chlorotolu- ron and 0.5 pg 1-1 for diuron during 1992.The Water Supply (Water Quality) Regulations 1989 state that individual pesti- cides and related products must not exceed 0.1 pg 1-1, or 0.5 pg 1-1 for total substances. As these limits are not uncom- monly exceeded, it is necessary to have a consistent method with good resolution and that is free from interference. The standard Standing Committee of Analysts' (SCA) method of analysis5 [double solvent extraction, one in alkaline conditions and the other in acidic conditions, followed by detection by high-performance liquid chromatography (HPLC) with ultraviolet (UV) absorbance at two wavelengths] suffers interference from other UV absorbers, and from a poor resolution of analytes (Figs.1 and 2). The proposed method is intended to provide a better alternative method of analysis. It involves derivatization of the urea herbicides by methylation of the amide group followed by separation by capillary gas chromatography (GC) and detec- tion by a nitrogen-phosphorus detector (NPD). The method was assessed for consistency of results, limits of detection, rates of recovery and linearity over the specified range, together with limits of determination of the derivatized products by GC-mass spectrometry (MS). Experiment a1 Reagents and Glassware All solvents were of HPLC grade (FSA Laboratory Supplies, Loughborough, Leicestershire, UK), with the water and methanol filtered through 0.45 pm membranes.The sodium hydride was in 80% dispersion with mineral oil (Aldrich Chemicals, Gillingham, Dorset , UK), the iodomethane (99%) was stabilized with copper (Aldrich) and the dimethyl sulfoxide was also of HPLC grade (Aldrich). A I B I ' \ \r e - Fig. l Spiked recovery from potable water by SCA method. (a) 0.1 pg ml-1 standard and (b) 0.1 pg 1-l spiked sample. Peak A = isoproturon and peak B = chlorotoluron1118 ANALYST, SEPTEMBER 1993, VOL. 118 The extraction cartridges were Octadecyl CIS (1 g) reversed- phase columns (J. T. BV Baker, Deventer, The Netherlands) fitted to a vacuum chamber (Supelchem UK, Saffron Walden, Essex, UK), with a vacuum pump (Charles Austin Pumps, Weybridge, Surrey, UK).Glassware for sample collection was rinsed with acetone, then with tap-water followed by ultra-high purity (UHP) water (Elgastat double ion-exchange resin and activated I I 1 I I I 1 lime - Fig. 2 Spiked recovery from potable water by SCA method. (a) 0.1 pg ml-l standard and (b) 0.1 pg 1y1 spiked sample. Peak A = linuron and peak B = diuron carbon columns, Elga, High Wycombe, Buckinghamshire, UK) and then with the sample. Glassware for analysis was washed with detergent and heated to 100 "C, cooled and rinsed with approximately 10% HCl, washed in acetone and finally in UHP water before baking for 1 h at 100 "C. Extraction Fix the solid-phase cartridges to a suitable vacuum chamber capable of reaching a maximum of 20 in (50.8 cm) of Hg vacuum.Condition the cartridges with 6 k 0.2 ml of filtered methanol followed by 6 k 0.2 ml of filtered water, making sure that the cartridges do not become dry. With vacuum off, apply 3 ml of UHP filtered water to the column. Add 1.0 1 k 10 ml of sample via poly- (tetrafluoroethylene) (PTFE) tubing and suitable PTFE connectors. Aspirate at a flow rate of 15 k 2 ml min-1. Wash the column with 3 k 0.5 ml of UHP filtered water. Dry under vacuum for 5 min. Time - Fig. 3 Mixed urea herbicide standard. 1.0 pg ml-1 standard. A, Isoproturon; B, chlorotoluron; C, linuron; and D, diuron L Temperature programme 190 "C 8 min 140°C L 0 . C min-' 10 min A Time - Fig. 4 Urea herbicides by proposed method (2.0 pg ml-1 standard).A, Monuron; B, isoproturon; C, chlorotoluron; D, linuron; E, diuron; F, methabenzthiazuron; and G, tebuthiuron il. I Time - Fig. 5 Spiked potable water (1 1). (a) 0.1 pg ml-l standard and (b) spiked sample A B D C c.-c. I I I 1 35.00 40.00 45.00 50.00 55.00 Time/min Fig. 6 Derivatized standard by GC-MS in SIM mode. Mixed standard, 5.0 pg ml-1. A, Isoproturon; B, chlorotoluron; C, linuron; and D, diuronANALYST, SEPTEMBER 1993, VOL. 118 1119 Table 1 Analysis of variance: proposed method Recovery (% 1 89.2 83.1 87.4 82.3 91.3 84.5 75.7 85.6 90.9 87.5 79.8 82.9 93.6 88.6 79.2 88.9 Degrees of freedoms 18.9 13.9 18.6 12.1 18.9 14.6 18.2 15.6 16.1 15.4 14.5 13.8 10.9 13.9 14.1 15.9 SW* 0.0122 0.0106 0.0129 0.0099 0.1625 0.1148 0.1815 0.1249 0.0105 0.0118 0.0125 0.0108 0.0726 0.1046 0.1211 0.1157 sbi o.Ooo1 0.0106 0.0129 0.0099 o.oO01 0.1141 0.0796 0.1057 0.0081 0.0102 0.0125 0.0123 0.1453 0.1141 0.1311 0.0907 Linford water 0.041 0.035 0.043 0.033 Mean Isoproturon 0.089 Chlorotoluron 0.083 Linuron 0.087 Diuron 0.082 Isoproturon 0.913 Chlorotoluron 0.845 Linuron 0.757 Diuron 0.856 Isoproturon 0.091 Chlorotoluron 0.088 Linuron 0.081 Diuron 0.083 Linford waterlo.1 pg 1-1 spike- Linford waterll.0 pg 1-1 spike- UHP waterlO.1 jig 1-1 spike- UHP waterll.O pg 1-1 spike- Isoproturon 0.936 Chlorotoluron 0.886 Linuron 0.792 Diuron 0.889 st* 0.0122 0.0159 0.0135 0.0183 0.1625 0.1618 0.1982 0.1637 0.0132 0.0156 0.0177 0.0164 0.1624 0.1547 0.1784 0.1471 UHP water 0.035 0.039 0.041 0.036 Limits of detectionlpg 1-1- Isoproturon Chlorotoluron Linuron Diuron * sw = Within-batch standard deviation.t s b = Between-batch standard deviation. * st = Total-batch standard deviation. @ Ref. 6. Table 2 Analysis of variance: SCA method Recovery (% 1 Degrees of freedoms Mean Isoproturon 0.076 Chlorotoluron 0.076 Linuron 0.073 Diuron 0.078 Isoproturon 0.768 Chlorotoluron 0.815 Linuron NDY Diuron ND Isoproturon 0.067 Chlorotoluron 0.071 Linuron 0.059 Diuron 0.076 Isoproturon 0.781 Chlorotoluron 0.825 Linuron 0.657 Diuron 0.661 Linford waterlO.1 pg I-' spike- Linford waterll.O pg I-' spike- UHP waterlO.1 pg I-' spike- UHP water11 .O pg 1- spike- SW* Sbt 0.009 0.011 0.018 0.023 0.014 0.006 0.019 0.019 0.017 0.012 0.026 0.029 76.1 76.1 72.5 77.7 12.1 16.8 4.7 5.4 76.8 81.5 ND ND 0.103 0.073 ND ND 0.103 0.073 ND ND 0.103 0.094 ND ND 19.1 15.9 ND ND 0.007 0.014 0.014 0.013 0.007 0.005 0.001 0.014 0.009 0.015 0.015 0.019 67.1 71.1 59.4 76.1 14.5 18.4 6.8 4.9 0.064 0.081 0.244 0.086 0.067 0.086 0.224 0.001 0.093 0.117 0.331 0.086 78.1 82.5 65.7 66.1 14.3 14.1 5.1 6.8 Limits of detectionlpg 1-I- Linford water 0.031 0.036 0.059 0.076 UHP water 0.023 0.046 0.046 0.043 Isoproturon Chlorotoluron Linuron Diuron * sw = Within-batch standard deviation. t sb = Between-batch standard deviation.* st = Total-batch standard deviation. @ Ref. 6. 7 ND = Not determined.1120 132 176 1, ' y 1177 ANALYST, SEPTEMBER 1993, VOL. 118 12031 50 45 40 - v) C 35 4- .- z g k 30 (II I & 25 X Q) m U 7 g 20 2 15 U 10 5 0 40 36 32 - v) c, .- 5 28 2 2 U 24 0 Y 0 20 Q) 5 16 -0 3 9 12 8 4 0 51 65 60 * '2 (a) 220 i' 100 140 180 220 174 c3702N 88 I I I 60 100 140 180 40 36 - 32 4- .- C 3 2 28 2 n & 24 c, .- - d z x 2o 8 + 16 C 3 12 8 4 0 5156 + 60 TH60N M+ I 226 I 100 140 180 220 '2 CBHGON / 2 c I M+ 60 100 140 180 220 m/z Fig.7 Mass spectra after derivatization. (a) Isoproturon, (b) chlorotoluron, ( c ) linuron and (d) diuron Elute the urea herbicides with 6 k 0.2 ml of filtered methanol, at a flow rate of 6 ml min-1, into a 10 ml centrifuge tube. Derivatization Evaporate the solvent residue to incipient dryness under a stream of nitrogen, while warming to approximately 40 "C. The nitrogen supply should be adjusted such that the surface of the solvent is just indented and no splashing occurs. Remove the tube from the nitrogen supply. Place approxi- mately 0.2 g of sodium hydride in a separate round-bottomed centrifuge tube, followed by 1 f 0.2 ml of diethyl ether.Evaporate to dryness under a stream of nitrogen. Add 1.5 k 0.2 ml of dimethyl sulfoxide to the tube and mix to form a suspension. One tube is required for three samples. Place approximately 300 f 50 yl of the sodium hydride suspension in the sample tube using a disposable pipette, and immediately add 50 k 5 yl of iodomethane. Leave standing in a fume cupboard for 10 min. In a fume cupboard add 1 k 0.2 ml of UHP water to the samples, taking care not to add too much too quickly as the sample can effervesce vigorously. Add 8 f 0.2 ml of diethyl ether to the sample, stopper the tube and shake vigorously for 2 min. Once the two phases haveANALYST, SEPTEMBER 1993, VOL.118 1121 separated, remove the supernatant organic phase with a clean disposable pipette and place in a clean, pointed centrifuge tube. Evaporate the extract to incipient dryness, accurately dilute to 1 ml with diethyl ether, and stopper the tube tightly. An analysis of variance (ANQVA)6 was carried out over 10 d to ensure at least ten degrees of freedom to assess the performance of the method (Table 1). Instrumentation The GC analyses were carried out using an AMS 92 gas chroma tograp h (Analytical Instrumentation , Cambridge, UK), fitted with an NPD, with the injector operated in split mode at a ratio of 30 : 1. The column was a fused-silica BP1 (25 m x 0.22 mm i.d., 0.25 pm film thickness) capillary column [SGE (UK), Milton Keynes, Buckinghamshire, UK].The operating parameters were: injector temperature 250 "C, detector temperature 250 "C, and column temperature 150 "C (isothermal). The total run time was approximately 8 min. The NPD was operated with the following gas flow rates: carrier (helium) 25 ml min-1, hydrogen 3 ml min-1, and air 150 ml min-1. The output was linked to an SP4400 Chromjet integrator (Spectra-Physics Analytical, Fremont, CA, USA). The GC-MS analysis was performed using an HP 5980 Series I1 gas chromatograph (Hewlett-Packard, Avondale, PA, USA) with an HP 5971A mass-selective detector; splitless injection was carried out for 1.5 min using an HP 7673 auto-injector. The fused-silica capillary column was a DB 1701 (60 m x 0.32 mm i.d. , 0.15 p,m film thickness) column (J & W Scientific, Folsom, CA, USA).Data acquisition and process- ing were performed by Microsoft MS-DOS 3.3 (Microsoft, Redmond, WA, USA], with mass calibration based on perfluorotributylamine (PFTBA). All mass spectra were obtained under electron-impact conditions (70 eV). The mass spectra were continuously scanned over the mass range 50-450 u at 0.5 s decade-'. Results Under the conditions described, separation of the four derivatized products was achieved (Fig. 3). With slight temperature programming, seven derived herbicides could be resolved (Fig. 4). Spiked recoveries were carried out on UHP water and a well water supply (Linford Well, Essex, UK) (see Table 1). A spiked recovery was also performed on a river-derived potable water (Hanningfield Final Water, Essex, UK), which shows few interference peaks (Fig.5). Calibration was over the range 0.1-8.0 pg 1-1 within which all analytes provided a linear response passing through the origin. Derivatized standards of 5.0 p,g 1-1 were run on the mass spectrometer as described (Fig. 6). From the data obtained it was possible to elucidate the structures of the derivatized products (Figs. 1 and 2). Discussion It can be seen that interference peaks and relatively poor recoveries make the previous methods for the determination of herbicides unsuitable for low-level analysis of river and potable waters (Figs. 7 and 8). The proposed method is based on methylation of the amide NH group to form a stable tertiary amide (Fig. 8). The reaction is a typical nucleophilic substitution reaction of the type shown below, where X is a readily displaced, stable leaving group R-X Sample-NH - Sample-N-R + HX Base 1 1 lsoproturon MI mlz= 148.2 M2 mlz= 72.2 1 1 Chlorotoluron MI mlz = 154.2 M2 mlz= 72.2 1 1 CI- L2 Linuron MI mlz= 175.1 M2 mlz = 88.2 Cl' L 2 Diuron MI mlz= 175.1 M2 mlz= 72.2 Fig.8 Structures of derivatized herbicides showing major fragmen- tation For urea herbicides, the leaving group is iodine, with the sodium hydride acting as a strong basic catalyst, and the reaction being achieved at ambient temperature. Efferves- cence of the acrid hydrogen iodide can be seen during the reaction. Separation of the four urea herbicides is achieved easily without the need for temperature programming, and although other peaks can be detected, they do not generally have the same retention time as the analytes and are of lower frequency than those for analysis by HPLC with UV detection.The limits of detection, calculated by multiplying the standard deviation of the mean of the low spikes by 3.3 (WRC, NS30, Revised June 1989)6 (Table l), are, in reality, much lower than the values stated, with peaks of concentration 0.02 pg 1-1 being seen for all analytes. The blank samples yielded no response and so could not be used for determining the limits of detection. For further confirmation of the derivatized product, the samples can be analysed by GC-MS in the selective-ion mode (SIM), searching for the base peak and molecular ion (Fig. 6). Comparison With Standard SCA Methods The standard SCA methods for the determination of urea herbicides involves sample concentration by extraction, evap- oration of the extract to incipient dryness, dissolution of the residue in the mobile phase, and analysis, using polar solvents, by HPLC with UV detection.1122 ANALYST, SEPTEMBER 1993, VOL. 118 In order to determine the four urea herbicides mentioned here, it is necessary to perform two separate extractions, one in alkaline conditions for isoproturon and chlorotoluron, and the other in acidic conditions for linuron and diuron.To gain the best response, they should be analysed at two separate wavelengths, viz., 240 and 220 nm, respectively. Although reasonable separation and response can be achieved by using this standard method (Figs. 1 and 2), at low levels of analyte in water (CO.1 pg 1-I), background peaks are significant and, without additional quantitative data, should be regarded as maxima (Figs. 1 and 2).Phenoxy acidic herbicides are a known contaminant, and, when present, the ureas have to be re-analysed at 270-280 nm. Because of the nature of UV detection and the fact that river and potable waters contain many UV absorbers, it is clear that analysis by GC-NPD will be much more selective. Recoveries performed on the same waters, and at the same concentrations, are generally about 10% lower for the SCA method, with comparable limits of detection (Tables 1 and 2). References 1 Department of the Environment Welsh Office, Guidance on Safeguarding the Quality of Public Water Supplies, HM Sta- tionery Office, London, 1990, pp. 99-102. 2 Worthing, C. R., and Hance, R. J., The Pesticide Manual, British Crop Protection Council, Farnham, Surrey, 9th edn., 1991, pp. 161, 322,507 and 520. 3 Ivens, G. W., The UK Pesticide Guide, British Crop Protection Council, Cambridge, UK, 1992, p. 18. 4 Essex Water Co., Water Quality Register, Chelmsford, Essex, 1992. 5 Standing Committee of Analysts, The Determination of Carba- mates, Thiocarbamates, Related Compounds and Ureas in Water, HM Stationery Office, London, 1987, pp. 15-21. 6 Water Research Centre, NS30-A Manual on Analytical Quality Control for the Water Industry, Marlow, Buckingham- shire, 1989, pp. 57 and 131. Paper 2104602 E Received December 14, 1992 Accepted February 25, 1993

ISSN:0003-2654    

DOI:10.1039/AN9931801117

出版商:RSC    

年代:1993

数据来源: RSC