ISSN:0003-2654    

DOI:10.1039/AN99318FP035

出版商:RSC    

年代:1993

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN99318FX037

出版商:RSC    

年代:1993

数据来源: RSC

ISSN:0003-2654    

DOI:10.1039/AN99318BX039

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, OCTOBER 1993, VOL. 118 117N Book Reviews Analysis of Paints and Related Materials: Current Tech- niques for Solving Coatings Problems Edited by William C. Golton. Pp. viii + 204. ASTM. 1992. Price f41 .OO. ISBN 0-8031-1465-6. There has been no comprehensive textbook on paint analysis since the Kappelmeier classic ‘Chemical Analysis of Resin- Based Coating Materials’ of 1959, nor is there likely to be. Modern paints are extremely complex and there are a large number of possible instrumental techniques available. Future publications are likely to be in the form of collections of individual papers written by experts, as is the present volume. This contains 11 papers, mostly written by analysts of the paint and related industries of the USA, and presented at an ASTM symposium in Pittsburgh on May 13-14, 1990.Most paints contain four groups of components, the pigments, binders, solvents (or water) and additives, which normally have to be separated prior to analysis. The easiest to deal with are the solvents, which can normally be identified by GLC. The pigments are usually separable by centrifuging and the additives by extraction or HPLC. The most difficult are the binders, which are best analysed by combinations of chromatographic methods for separation, and spectroscopic methods for identification. A very salient point is made in the first paragraph of the first paper, which points out that the complete analysis of a paint requires a whole set of modern analytical techniques, and a great deal of experience. Unfortu- nately at the present time too much attention is given to the former requirement and too little to the latter.‘A very salient point is made in the fist paragraph of the first paper, which points out that the complete analysis of a paint requires a whole set of modem analytical techniques, and a great deal of experience’ This first paper, by Schernau et al., dealing with analysis of the wholc paint reviews the current chromatographic and spectroscopic techniques, with accounts of some of the newer developments, namely, diffuse-reflectance FTIR (DRIFTS) for opaque samples, I R microscopy for looking at paint layers and FT-NMR. The next, by Simonsick, Jr., reviews GC-MS and pyrolysis GC-MS techniques. Coming to individual classes of components Sheih and Benton report on HPLC techniques for analysis of bisphenol A-, novolac- and aliphatic epoxy resins.Size-exclusion chromatography, de- scribed by Cheng-Yih Kuo and Provder, originally called GPC, has been universally used for determining the relative molecular mass of coatings polymers and now has to extend its scope to cover the newer polymers required for the environ- mentally acceptable coatings, e.g., waterborne, high-solids and powder. Advances in available detectors have been particularly valuable. Coming to the pigment component, X-ray techniques, as reviewed by Snider, are often required. These are usually X-ray diffraction for structural analysis and X-ray fluores- cence for elemental analysis. Combinations of SEM and X-Ray spectrometry have proved invaluable for studying paint defects.Various GC techniques, as reported by Young, are universally used, either direct for analysing the solvents and low relative molecular mass components, or following pyrolysis for those with higher relative molecular masses. Head-space analysis has proved to be very useful for some problems. Analysis of cured films is even more difficult than that of liquid paints. Hartshorn reports on the study of the curing and ageing of autoxidatively drying products by FTIR, and van der Ven rt ul. on the curing of two-component polyurethanes. The surfaces of polymers often have diffcrcnt compositions from the bulk polymer. Gerdolla, Jr., reviews the current photo- electron and ion spcctroscopic techniques used for studying polymer surfaces, namely, ESCA, SIMS and ISS.New accessories for use with FTIR, namely diffuse reflectance, IR microscopy and photoacoustic are all described by Millon and Julian and three studies of coatings failure by Tator and Weldon. The book is well produced, in hard cover, with references to each paper, which has been peer reviewed. L. A. O’Neill Chemical Sensor Technology. Volume 4 Edited by Shigeru Yamauchi. Pp. xviii + 270. Elsevier. 1992. Price US$191.50; Dfl. 335.00. ISBN 0-444-98680-4; 4-06-205458-2 (Japan). This book contains an eclectic collection of chapters written by authors from the USA, Europe and Japan. Not surprisingly in a book that has been assembled by a Japanese editor, authors from Japan predominate. In some senses this is a courageous book, for the implication of the title is that the contributions are linked to technological aspects of sensors, by which I understand, the development of sensor types that have already been defined and researched in laboratories to the point where they are ‘near market’ devices.Certainly some of the chapters achieve this end admirably but others are obviously accounts of recent scientific research, which although worthy in themselves, could not be described as technology in its strictest sense. This, however, is a minor problem in a book that I enjoyed greatly. The opening chapter is an account of Taguchi’s heroic development of the TGS gas sensor. True, the chapter narrowly escapes being hagio- graphic, nonetheless I would be tempted to recommend the book on this contribution alone. It is a timely reminder to the scientific and technological policy makers that inventiveness and effort is not just to be found in substantial highly organized research groups working in well-founded schools, but can be found in the efforts of talented individuals anywhere on earth! Subsequent chapters develop themes such as: technologies for sensor fabrication; miniaturization of catalytic sensors; sensitization of dielectric surfaces by chem- ical grafting, application to ISFETS and ENFETS; and high-sensitivity immunosensors employing surface photovol- tage techniques.The distinctly applied nature of the book can be seen in the chapter on “on-invasive Monitoring of Glucose in Blood’ where an ISFET sensor is coupled to a suction- effusion device. Chapters such as this should help to focus the minds of those involved in sensor research so that they are always cognizant of the eventual destination of their device and its associated technology.I have a few words of minor criticism about this book. There appears to be no particular structure or rationale to the choice of topics that make up the chapters, nor is there any notable organization of the chapters within the book. This makes sensor research look rather haphazard when, in fact, there are a number of well developed and distinct lines. A rather more significant deficiency is the lack of optical sensing papers and papers on other more unusual transducers such as impedance or temperature sensing devices. This gives a somewhat biased118N ANALYST, OCTOBER 1993, VOL. 118 picture of the field of sensor technology.The book finishes with an excellent index that is accurate and extensive. This distinguishes it from some of the collections of conference papers that masquerade as research or technological mono- graphs but which lack the primary courtesy of providing any detailed means of accessing the information therein. I have enjoyed this book and would recommend others to read it as well. Tony E. Edmonds Biological Magnetic Resonance. Volume 11. In Vivo Spectroscopy Edited by Lawrence J. Berliner and Jacques Reuben. Pp. xiii + 334. Plenum. 1992. Price US$85.00 ISBN 0-306- 44276-0. This volume is the latest in a series concerned with techniques and applications of NMR and ESR spectroscopy. Volume 11 contains seven chapters generally concerned with in vivo spectroscopy and, to a lesser extent, magnetic resonance imaging.Chapter 1 on ‘Localization in clinical NMR spectro- scopy’ begins very usefully with a good description of basic nuclear properties and NMR parameters of biological interest. One of the problems of the use of NMR imaging techniques to obtain spectra of only specific regions of a sample, is that NMR resonances from within one region but with different chemical shifts will appear to come from different regions. Whilst this problem is discussed, some information on the magnitude of the effect would be useful to the interested non-specialist. The chapter is restricted to a description of techniques and no examples are actually given of localized clinical NMR spectra. Chapter 2 is concerned with an explanation of using off-resonance irradiation in NMR and the title includes ‘in vivo MRS and MRI applications’.This is a long and highly theoretical chapter with a number of computer simulated experiments. Most of the applications are concer- ned with the dynamics of proteins in solution or tissue homogenates rather than in vivo, although right at the very end of the chapter, an example of how off-resonance irradiation can improve NMR images is shown. The NMR methods for probing brain ischaemia are the subject of Chapter 3. This section of the book has a good practical ‘the volume contains reviews covering a wide range of biological magnetic resonance approaches and, in general, will be of use to the reader interested in the applications’ section and explains how 31P and 1H NMR using surface coil and localization techniques can give information on brain biochemistry.The authors provide a detailed guide on how the spectral results can be quantified with the many assumptions well discussed and they are realistic in not ignoring the substantial problems. Chapter 4 is concerned with 23Na NMR spectroscopy in biology where it is used to measure sodium flux into and out of cells. The chapter contains a well- referenced background section and is clear on the theory and on application areas of 23Na NMR. This is a very practical chapter with a good critique of the experimental approaches and describes the assumptions involved in quantification of the results. A chapter entitled ‘In vivo 19F NMR’ comes next in the book. This approach promises to be very useful because of the high sensitivity of 1YF NMR, and a number of applications have appeared in the literature over the last few years.It is a pity that the references are mainly limited to 1988 and earlier, and this book is therefore describing at best work that is five years old. The main areas of application of *9F NMR spectroscopy are to study the distribution and metabolism of drugs and model compounds and to monitor intracellular pH through the use of specially designed molecules, which can penetrate cells; 1gF NMR imaging of drugs in vivo in a major goal and is also discussed. Chapter 6 is devoted to another potentially important biological NMR nucleus, namely 2H. This has found application as a monitor of drug metabolism and for measuring blood flow in vivo, for example to tumours, by observing the washout of a D20 NMR signal with time after a single injection.This chapter provides a good review of the literature but is short on experimental details. Chapter 7, on ESR, is a short section that describes the new and difficult exploratory experiments in ESR imaging, ESR spectroscopic studies of nitroxide reduction in vivo and the identification of endogenous free radicals using spin traps. It finishes on an intriguing note-the trapping of drug intermediates. Overall the volume contains reviews covering a wide range of biological magnetic resonance approaches and, in general, will be of use to the reader interested in the applications. The problem of such a varied content is that individuals will not want to buy a volume for one article but libraries will find it a useful addition to their shelves.J . C. Lindon Electrochemical Oxygen Technology By Kim Kinoshita. The Electrochemical Society Series. Pp. xvi + 432. Wiley. 1992. Price f98.00. ISBN 0-471-57043-5. Not so much a book for practising analytical chemists as one that is a reference source for researchers. The book covers the general physicochemical properties of oxygen and its electro- chemistry as a basis for the next chapter, which considers the preparation and properties of oxygen electrodes, wherein there is a good and well-explained discussion of various electrode structures for oxygen reduction and evolution. An extensive range of electrode types are then described in the following chapters under the headings of fuel cells, metauair batteries and oxygen recombination in batteries.In each case, this is done under various sub-divisions with much interesting information and the basis of ideas being drawn from the published literature. Among the interesting points are those involving the phosphoric acid fuel cell, with the mention that these are the closest to commercialization with field tests of power plants up to 4.8 MW having been completed! This point emphasizes that electrochemical tech- nology is very widely based, and that the provision of a book for analytical chemists is a prospect that has to be separately addressed. Nevertheless, as mentioned, this can be an information source for researchers thirsting for ideas. For this purpose the text is well supplied with diagrams, detailed tables and a host of references. ‘Not so much a book for practising analytical chemists as one that is a reference source for researchers’ It is only in the final chapter, on industrial electrochemistry, that analytical prospects and applications are specifically addressed. This being in a 13 page discussion of oxygen sensors of potentiometric and amperometric types along with the detection of hydrogen peroxide and ozone. Therefore, analytical chemists might prefer to stick to the ‘Measurement of Dissolved Oxygen, Chemical Analysis’, by M. L. Hitch- man, from the same publishing house, and perhaps to also turn to some of the other ten references on oxygen sensors given on p. 420 of this book. J. D. R . Thomas

ISSN:0003-2654    

DOI:10.1039/AN993180117N

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, OCTOBER 1993, VOL. 118 119N Conference Diary Date Conference November 1-3 2 2 4 3 3-5 7-10 7-1 1 7-12 8-10 11-12 11-12 12-13 14-1 9 14-1 9 15-19 22-23 Location Chernyaev Conference on Chemistry, Moscow, Analysis, Technology and Application of Platinum Metals Electro-Membrane Processes London, Russia UK KEMIA 93. Finnish Chemical Congress and Exhibition Finland Helsinki, Pharmaceutical Applications and Sample York, Handling Techniques UK 2nd International Symposium on Characterization and Control of Odours and VOC in the Process Industries Louvain-la-Neuve , Belgium Electrophoresis '93 Charleston, SC, USA 7th International Forum-Electrolysis in Lake Buena Chemical Manufacture Vista, FL, USA Symposium on Supercritical Fluid Phenomena St. Louis, MO, (1993 Annual Meeting of the AIChE) USA International Symposium on Plasma PolymerizatiodDeposition International Conferences on Analytical Chemistry, Biochemistry, Pharmaceutical Sciences, and Water Quality/Environmental Pollution 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 Quality/Environmental Pollution Las Vegas, NV, USA New Delhi, India San Diego, CA, USA Clearwater Beach, FL, USA Melbourne, Australia San Jose, CA, USA New Jersey, USA Shanghai, China Contact 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, Sociktd 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: +1 301 898 5596 Dr. N. Weinberg, 72 Ward Road, Lancaster, NY Tel: +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: + 1 203 432 4375. Fax: + 1 203 432 7232 K. L. Mittal, Skill Dynamics (an IBM Company), 500 Columbus Ave., Thornwood, NY 10594, USA Tel: + 1 914 742 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. 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: +1 904 392 6664. Fax: +1 904 392 4911 1993 IFCC Congress Secretariat, 232 Bridge Road, Richmond, Victoria, Australia Tel: +61 3 429 4322. Fax: +61 3 427 0715 IEEELEOS, 445 Hoes Lane, P.O. Box 1331, Piscataway, NJ 08855-1331, USA Tel: +1908 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. 14086-9779, USA CT 06520-2159, USA120N ANALYST. OCTOBEK 1993, VOL. 118 Date Conference Location 30-3/12 13th International Symposium on HPLC of San Francisco, Proteins, Peptides and Polynucleotides CA, USA December 6-8 International Symposium on Purity Stockholm, Determination of Drugs Sweden 7-9 The First Conference in Chemistry and its Doha, Applications Qatar 8-10 Laser M2P, Materials Engineering, Medicine Lyon, and Biology, Physics and Chemistry France 1994 January 5-7 6th Winter Conference on Flow Injection San Diego, CA, Analysis USA 10-15 1994 Winter Conference on Plasma San Diego, CA, Spectrochemistry USA 1 1-14 5th International Symposium on Supercritical Baltimore, MD, 19-21 2nd International Conference on Reactive Yokohama, Fluid Chromatography and Extraction USA Plasmas and 11th Symposium on Plasma Japan Processing High Performance Capillary Electrophoresis USA 31-3/2 HPCE '94: Sixth International Symposium on San Diego, CA, February 13-17 Second International Glycobiology San Francisco, Symposium: Current Analytical Methods CA, USA 21-25 OFC '94: Optical Fibre Communications San Jose, CA, Conference USA 22-25 HTC 3: Third International Symposium on Antwerp, Hyphenated Techniques in Chromatography Belgium 2 8 4 3 Pittcon '94: The 45th Pittsburgh Conference on Chicago, IL, Analytical Chemistry and Applied USA Spectroscopy March 7-1 1 4th International Symposium on Trends and Dresden, Germany New Applications in Thin Films 13-16 Third European Federation of Corrosion Estoril, Workshop on Microbial Corrosion Portugal Contact Ms.Paddy Batchelder, Conference Manager, 7948 Foothill Knolls Drive, Pleasanton, CA 94588, USA Tel: +1 510 426 9601. Fax: +1 510 846 2242 Swedish Academy of Pharmaceutical Sciences, P.0. Box 1136, S-111 81 Stockholm, Sweden Tel: +46 8 245085. Fax: +46 8 205511 Professor Abdel-Fattah M. Rizk, Department of Chemistry, Faculty of Science, University of Qatar, P.O. Box 2713, Doha, Qatar Richard MoncorgC, Universite de Lyon 1, Bat. 205, F-69622 Villeurbaniie Cedex, France 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, '30 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. Paddy Batchelder, P.O. Box 370, Pleasanton, CA 94566, USA Tel: +1 510 426 9601. Fax: +1 510 846 2242 Meetings Department, Optical Society of America, 2010 Massachusetts Avenue, NW, Washington, DC Tel: + 1 202 223 9034. Fax: + 1 202 416 6100 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 20036-1023, USA Frank Richter, TU Chemnitz, FB Physik, PSF 964, D-09009 Chemnitz, Germany Fax: +49 371 852491 CCsar Sequeira, Instituto Superior Tecnico, Av.Rovisco Pais, 1006 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, SwedenANALYST, OCTOBER 1993, VOL. 118 121N Date 13-18 27-30 April 6-8 10-13 10-15 10-16 12-14 17-19 18-22 19-22 May 7-12 8-12 8-13 8-13 Conference Locat ion 207th American Chemical Society National Meeting USA San Diego, CA, 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 6th International Conference on Near Infrared Lorne , Spectroscopy Australia ANALYTICA'94: 14th International Munich, Conference on Biochemical and Instrumental Analysis Germany Food Structure Annual Meeting Toronto, Ontario, Canada 85th AOCS Annual Meeting & Expo Atlanta, GA, USA HPLC '94, Eighteenth International Minneapolis, Symposium on Column Liquid MN, Chromatography USA CLEO '94: Conference on Lasers and Electro- Anaheim, CA, Optics USA Con tact Department of Meetings, American Chemical Society, 1155-16th 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 (01865 310981 Mr. B. R. Hodson, American Chemical Society, 1155-16th Street N. W., Washington, DC 20036, USA Tel: +1202 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, IA 52244, 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: +1319 335 5649, Fax: +1319 335 5777; and Dr.Jon Doi, Roy F. Weston, Inc., 1 Weston Way, West Chester, PA 19380, USA Tel: + 1 215 524 6167. Fax: + 1 215 524 6175 NIR-94, Peter Flinn, Pastoral and Veterinary Institute, Mt. Napier Road, Private Bag 105, Hamilton, Victoria 3300, Australia Tel: +61 55 730915. Fax: +61 55 711523 Miinchener Messe- und Ausstellungsgesellschaft mbH, Analytica '94/Werbung Postfach 12 10 09, D-8000 Miinchen 12, Germany Tel: +49 89 51 07 143. Fax: +49 89 51 07 177 Dr. Om Johari,, SMI, Chicago (AMF O'Hare), IL Tel: +1 708 529 6677. Fax: +1 708 980 6698 AOCS EducatiodMeetings Department, P. 0. Box 3489, Champaign, IL 61826-3489, USA Tel: +1217 359 2344. Fax: +l 217 351 8091 Ms.J. E. Cunningham, Barr Enterprises, P.O. Box 279, Walkersville, MD 21793, USA Tel: +1 301 898 3772. Fax: +1 301 898 5596 Meetings Department, Optical Society of America, 2010 Massachusetts Avenue, NW, Washington, DC Tel: +1 202 223 9034. Fax: +1202 416 6100 60666-0507, USA 20036-1023, USA122N ANALYST, OCTOBER 1993, VOL. 118 Date 9-13 16-19 16-20 22-26 24-27 24-27 29-1/6 30-2/6 30-1/6 June 1-3 5-7 5-1 1 6-8 8-1 1 12-15 15-17 15-18 Conference Location Focus 94-The Annual National Meeting and Brighton, Exhibition of the Association of Clinical UK Biochemists 24th Annual Symposium on Environmental Ottawa, Analytical Chemistry Canada .. 24th International IAEAC Symposium on Environmental Analytical Chemistry Canada Ottawa, Ontario, ESEAC '94: 5th European Conference on Electroanalysis Italy Venice, 3rd Symposium on Molecular Chirality Kyoto, Japan International Symposium on Metals and Genetics: Toxic Metal Compounds in Environment and Life 5 ; Interrelation between Chemistry and Biology 42nd ASMS Conference on Mass Spectroscopy Chicago, IL, USA 14th Nordic Atomic Spectroscopy and Trace Naantali, Analysis Conference Finland Toronto, Ontario, Canada Scandinavian Symposium on Infrared and Bergen, Raman Spectroscopy Norway Biosensors 94-The Third World Congress on New Orleans, Biosensors USA VIth International Symposium on Bruges, Luminescence Spectrometry in Biomedical Belgium Analysis-Detection Techniques and Applications in Chromatography and Capillary Electrophoresis 24th ACHEMA Conference on Plasma Science Frankfurt, Germany Santa Fe, NM, USA 6th International Conference on Flow Analysis Toledo, Spain 1994 PREP Symposium and Exhibit Washington, DC, USA 16th Symposium on Applied Surface Analysis (ASSD) USA Burlington, MA, The Second International Symposium on Speciation of Elements in Toxicology and Environmental and Biological Sciences Loen, Norway Con tact 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, Symposium on Molecular Chirality (SMC), Faculty of 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 ASMS, 815 Don Gaspar, Santa Fe, NM 87501, USA Tel: +1 505 989 4517. Ari Ivaska, Abo Akademi University, Laboratory of Analytical Chemistry, Biskopsgatan 8, SF-20500 Abo Turku, Finland Dr. Alfred Christy, Department of Chemistry, University of Bergen, N-5007 Bergen, Norway 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 Professor Dr. Willy R. G. Baeyens, Symposium Chairman, University of Ghent , Pharmaceutical Institute, Department of Pharmaceutical Analysis, Laboratory of Drug Quality Control, Harelbekestraat 72, B-9000 Ghent, Belgium Tel: +32 9 221 89 51. Fax: +32 9 221 41 75 Dechema, Theodor Heuss-Allee 25, P.O. Box 970146, D-W-6000 Frankfurt am Main 97, Germany A. Perratt, Los Alamos National Laboratory, Group X-10, MS D-406, P.O. Box 1663, Los Alamos, NM 87545, USA Professor M. ValcarceVDr. M. D. Luque de Castro, (Flow Analysis VI), Departamento de Quimica Analitica, Facultad de Ciencias, E-14004 Cordoba, Spain Tel: +34 57 218616.Fax: +34 57 218606 Ms. Janet Cunningham, Symposium/Exhibit Manager, Barr Enterprises, P.O. Box 279, Walkersville, MD 21793, USA Tel: +1 301 898 3772. Fax: 4-1 301 898 5596 Joseph Geller, Geller Microanalytical, 1 Intercontiental Way, Peabody, MA 01960, USA Tel: + 1 508 535 5595. 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, NorwayANALYST, OCTOBER 1993, VOL. 118 123N Date 16-17 16-17 19-24 27-117 July 3-7 18-22 20-22 Conference 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 Location Toronto, Canada Toronto, Canada Bournemouth, UK Espoo, Suomi-Finland Contact 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 International Chemometrics Research Meeting Veldhoven Mrs.Gerrie Westerlaken, Conference Organizing Bureau VNW, Postbus 1558,6501 BN Nijmegen, Tel: +31 80 234471. Fax: +31 80 601159 B. Jouffrey, SFME 67, rue Maurice Gunsbourg, Tel: +33 1 46702844. Fax: +33 1 46708846 Dr. Steve Hill, Department of Environmental Plymouth, Devon, UK PL4 8AA (Eindhoven), The Netherlands The Netherlands Paris, XI11 International Congress on Electron Microscopy France 94205, Ivry sur Seine cedex, France Seventh Biennial National Atomic Hull, Spectroscopy Symposium UK Sciences, University of Plymouth, Drake Circus, August 2-6 The Second Changchun International Changchun, Symposium on Analytical Chemistry(C1SAC) China 8-12 IGARSS '94: 1994 International Geoscience Pasadena, CA, and Remote Sensing Symposium USA 21-26 208th ACS National Meeting (with Sessions of Washington, Analytical Chemistry, Environmental DC, Chemistry, Chemical Health and Safety, efc ) USA Conference Hungary 29-2/9 13th International Mass Spectrometry Budapest, September 5-9 7th International Symposium on Synthetic Tubingen, Membranes in Science and Industry Germany 11-16 EUCMOS XXII: XXIInd European Congress Essen, on Molecular Spectroscopy Germany 12-15 Separations for Biotechnology 12-15 3rd International Symposium on Environmental Geochemistry Reading, UK Krakow, Poland 13-18 3rd International Symposium on Mass San Francisco, Spectrometry in the Health and Life Sciences CA, USA 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, 1155-16th Street N.W., Washington, DC 20036, USA Hungarian Chemical Society, H-1027 Budapest, Hungary Tel: +36 1201 6883. Fax: +36 1 15 61215 20036-1023, USA Dechema, P.O. Box 970146, D-W-6000 Frankfurt am Main 97, Germany GDCh-Geschaftsstelle, Ab t . Tagungen, 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 SCI Conference Office, 14/15 Belgrave Square, London, UK SWlX 8PS Tel: +44 71 235 3681. Fax: +44 71 823 1698 Helios Rybicka, Faculty of Geology, Geophysics and Environmental Protection, University of Mining and Metallurgy, Al.Mickiewicza 30, PL-30-059 Krakow, Poland Tel: +48 12 333290. Fax: +48 12 332936 Marilyn Schwartz, Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 9413-0446, USA124N ANALYSI’, OCTOBER 1993, VOL. 118 Date Conference Location 19-21 The Second International Conference on Aveiro, Applications of Magnetic Resonance in Food Science 19-23 XIIIth International Symposium on Medicinal Paris, Chemistry France Portugal 21-23 7th International Symposium on Bournemouth, Environmental Radiochemical Analysis UK 21-23 5th International Symposium on Stockholm, Pharmaceutical and Biomedical Analysis Sweden 22-24 12th National Conference on Analytical Constanta, Chemistry Romania 25-28 5th International Symposium on Chiral Stockholm, Discrimination Sweden October 2-7 29th Annual Meeting of the Federation of Analytical Chemistry and Spectroscopy USA Societies 3-6 PREP ’94: 11th International Symposium on Baden-Baden, Preparative and Industrial Chromatography Germany St.Louis, MO, 17-19 3rd International Symposium on Supercritical Strasbourg, Fluids France 3 0 4 1 1 OPTCON ’94 Boston, MA, USA November 9-11 11th Montreux Symposium on Liquid Montreux, Chromatography-Mass Spectrometry (LC/ Switzerland MS; SFCMS; CE/MS; MSMS) 10-1 1 17th International Conference on Chemistry, New Delhi, Bio Sciences, and Environmental Pollution India 18-22 Joint Oil Analysis Program International Pensacola, FL, Condition Monitoring Conference USA 1995 February 19-24 OFC ’95: Optical Fibre Communication San Diego, CA: Conference USA Contact Dr.A. M. Gil, Department of Chemistry, University of Aveiro, 3800 Aveiro, Portugal CONVERGENCESDSMC ’94, 120 avenue Gambetta, 75020 Paris, France Fax: +33 1 40 31 0165 Dr. P. Warwick, Department of Chemistry, Loughborough University of Technology, Loughborough, Leicestershire, UK L E l l 3TU Tel: +44 509 222585 or +44 509 222545. Fax: +44 509 233163 Swedish Academy of Pharmaceutical Sciences, P. 0. Box 1136, S-111 81 Stockholm, Sweden Tel: +46 8 245085. Fax: +46 8 205511 Dr. G.-L. Radu, Romanian Society of Analytical Chemistry 13 Bul. Carol I, Sector 3, 70346 Bucharest, Romania Swedish Academy of Pharmaceutical Sciences, P. 0. Box 1136, S-111 81 Stockholm, Sweden Tel: +46 8 245085. Fax: +46 8 205511 FACSS, P.O. Box 278, Manhattan, KS 66502-0003, USA Tel: + 1 301 846 4797. GDCh-Geschaftsstelle, Abt. Tagungen, 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 Congres ‘Fluides Supercritiques’ Mle Brionne, ENSIC B.P. 451-1, rue Grandville, F-54001 Nancy Cedex, France Tel: +33 83 17 50 03. Fax: +33 83 35 08 11 Meetings Department, Optical Society of America, 2010 Massachusetts Avenue, NW, Washington, DC Tel: +1 202 223 9034. Fax: +1 202 416 6100 20036-1023, USA M. Frei-Hausler, Postfach 46, CH-4123 Allschwil2, Switzerland Tel: +41 61 4812789. Fax: +41 61 4820805 Dr. V. M. Bhatnagar, Alena Chemicals of Canada, P.O. Box 1779, Cornwall, Ontario, Canada K6H 5V7 Tel: +1 613 932 7702. Technical Support Center, Joint Oil Analysis Program, Bldg. 780, Naval Air Station, Pensacola, FL 32508, USA Tel: + 1 904 452 3191. Meetings Department, Optical Society of America, 2010 Massachusetts Avenue, NW, Washington, DC Tel: +1 202 223 9034. Fax: +1 202 416 6100 20036-1023, USA 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/AN993180119N

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

1248 ANALYST, OCTOBER 1993, VO12. 118 ng ml-l iodide. The iodide comparator standards were prepared by transferring microlitre portions of the iodide standard solution onto pre-cleaned Gelman Sciences GA-6S membrane filters (0.45 pm pore size, 47 mm diameter) placed in pre-cleaned 1.2 ml polyethylene irradiation vials. The comparator standards and samples were prepared to have identical geometry. Reference Materials A number of CRMs and Standard Reference Materials (SRMs) obtained from the IAEA and the National Institute of Standards and Technology (NIST) , respectively, were analysed to evaluate the accuracy of the methods at the low levels of iodine that might be present in some biological and diet samples. The RMs used were: NIST SRM 1571 Orchard Leaves and SRM 1577 Bovine Liver, and IAEA A-11 Milk Powder.H-4 Animal Muscle and H-9 Mixed Human Diet. Irradiation and Counting All samples and comparator standards were irradiated in the Dalhousie University SLOWPOKE-2 research reactor at a maximum integral neutron flux of 1 x 1012 n cm-2 s-1 or a maximum epi-cadmium neutron flux of 1 x lo'* n cm-2 s - I . They were counted on a 25 ml active volume Aptec hyperpure Ge detector connected to a Link high count rate pulse processor and a Nuclear Data ND-66 analyser. The detector had a resolution of 2.08 keV (full-width at half-maximum) at the 1332 keV photopeak of 6OCo. The 443 kcV y-ray of 12*l was free from interference and was therefore used for assaying iodine. Microwave Acid Digestion of Samples Microwave acid digestion bombs (Parr Instrument Co.) were used for the dissolution of samples.The bomb contained a chemically inert Teflon sample cup of 45 ml capacity. Details of the development of the sample digestion procedure are given clsewhere.29 Briefly, 200-250 mg of a sample were accurately weighed into a pre-cleaned Teflon sample cup, 5 ml of ultrapure concentrated nitric acid were added, and the mixture was heated for 35 s at a power of 675 W in a microwave oven. The digestion step was repeated after a 20 rnin cooling period, if necessary. This procedure yielded sufficiently complete decomposition of the sample with respect to iodine. The contents of the cup were poured into a pre-cleaned 250 ml beaker containing 1 g of hydrazine sulfate. The cup and its lid were rinsed successively with 3 x 5 ml aliquots of each of a 5% hydrazine sulfate solution and DDW.The washings were added to the sample solution. The resulting solution was diluted to 100 mi, maintaining a final acidity of 0.2 rnol 1-l. Preconcentration of Iodine by Bismuth Sulfide Coprecipitation Details of the development of this method have recently been published.'" Bricfly, it involved the sequential dropwise addition of 1 ml of each of bismuth nitrate and thioacetamide stock solutions to a 100 ml digested sample solution at an acidity of 0.2 rnol I-'. The dark brown precipitate formed was allowed to settle for 20 rnin at room temperature and then filtered through a pre-cleaned Gelman membrane filter under vacuum suction. The precipitate was washed three times with 5 ml aliquots of a 0.2 mol I-' nitric acid solution containing 0 .I% hydrazine sulfate. The filter containing the precipitate was folded, placed in a 1.2 ml polyethylene vial and heat- sealed. The vial was irradiated in an epi-cadmium neutron flux of 1 .0 x 1010 n cm-2 s- for 30 or 60 min and counted for either 30 or 60 rnin after a decay period of I min. Preconcentration of Iodine by Toluene Extraction The digested sample solution was poured into a 250 ml beaker. The sample cup and lid of the microwave digestion bomb were thoroughly rinsed with 2 x 5 ml portions of a 5% hydrazine sulfate solution and subsequently with 2 x 5 ml portions of DDW. The washings were added to the sample solution and the final acidity of the resulting solution was adjusted to between 1 and 2 rnol I-', maintaining a total volume of 30 ml.This solution was transferred into a 125 ml Pyrex separating funnel. Then, 10 ml of toluene and 5 ml of a 10% NaN02 solution were added. Iodine was extracted into the organic phase by shaking on a wrist-action mechanical shaker for 10 min. The organic phase was transferred into another separat- ing funnel. The extraction procedure was repeated three times with 10 ml of toluene and 2 ml of a 10% NaN02 solution. The extraction recovery of iodine was checked by irradiating 1 mi aliquots of the organic phasc after each extraction and calculating the yield of iodine. Preliminary experiments with spiked standard iodine and with 1251 tracer revealed that three extractions were sufficient for the complete recovery of iodine (>99%).The organic phases were combined in a separating funnel. The iodine was reduced to iodide and back-extracted into the aqueous phase by equilibrating with 2 x 10 ml portions of a 5% hydrazine sulfate solution. The aqueous phases containing iodide were combined and diluted to 100 ml, maintaining a final acidity of 0.2 mol I-' with rcspect to nitric acid. Samples containing relatively large amounts of chlorine and bromine were first treated by this toluene cxtraction method to isolate iodine. Then, the bismuth sulfide coprecipitation procedure described above was used to concentrate the iodide further and collect it in a precipitate which is suitable for NAA. The iodine content of the precipitate was measured by irradiating in an epi-cadmium neutron flux of 1 x 1OlO n cm-? s-I for 60 rnin and counting for 60 rnin after a decay period of 1 min.Radiochemical Separation of Iodine by Bismuth Sulfide Coprecipitation About 250 mg of a sample were accurately weighed into a pre- cleaned polyethylene vial and irradiated for 60 min in an integral neutron flux of 1 X 1012 n cm-? s-I. The vial was opened and the sample was transferred into a Teflon sample cup of the microwave digestion bomb. The vial was rinsed three times with 1 ml portions of ultrapure concentrated nitric acid. The irradiated sample was spiked with 100 pI of 1251 tracer solution and digested according to the procedure described under Microwave Acid Digestion of Samples. To the digested sample solution, 2 ml of bismuth nitrate stock solution, 1 ml of ammonium iodide (1 mg ml-I I - ) and 2 ml of thioacetamide stock solution were added sequentially while stirring the solution with a magnetic stirrer.The resulting dark brown precipitate was allowed to settle for 20 min and then filtered through a Gelman membrane filter under vacuum suction. The entire procedure was completed within 50 min from the end of the irradiation. The filter was folded, placed in a new 1.2 ml polyethylene vial and counted for 30 min. The recovery of iodine was checked by measuring the activity of the 1251 tracer. Radiochemical Purification by Palladium Iodide Precipitation Thc sample was digested according to the procedure described under Microwave Acid Digestion o f Samples. This solution was taken through the bismuth sulfide coprecipitation proce- dure.The precipitate was collected and irradiated for 60 rnin in an integral neutron flux of 1 X 1012 n cm-2 s-I. The irradiated precipitate was washed off the filter into a beaker with 5 ml of concentrated nitric acid. The filter was rinsed thoroughly with 4 mol I-' nitric acid and subsequently with 10 ml of a 5% hydrazine sulfate solution. The sample solution was diluted to SO ml with DDW, maintaining a final acidity between 2 and 4 rnol I-'. To this solution, 0.5 ml aliquots of1248 ANALYST, OCTOBER 1993, VO12. 118 ng ml-l iodide. The iodide comparator standards were prepared by transferring microlitre portions of the iodide standard solution onto pre-cleaned Gelman Sciences GA-6S membrane filters (0.45 pm pore size, 47 mm diameter) placed in pre-cleaned 1.2 ml polyethylene irradiation vials.The comparator standards and samples were prepared to have identical geometry. Reference Materials A number of CRMs and Standard Reference Materials (SRMs) obtained from the IAEA and the National Institute of Standards and Technology (NIST) , respectively, were analysed to evaluate the accuracy of the methods at the low levels of iodine that might be present in some biological and diet samples. The RMs used were: NIST SRM 1571 Orchard Leaves and SRM 1577 Bovine Liver, and IAEA A-11 Milk Powder. H-4 Animal Muscle and H-9 Mixed Human Diet. Irradiation and Counting All samples and comparator standards were irradiated in the Dalhousie University SLOWPOKE-2 research reactor at a maximum integral neutron flux of 1 x 1012 n cm-2 s-1 or a maximum epi-cadmium neutron flux of 1 x lo'* n cm-2 s - I .They were counted on a 25 ml active volume Aptec hyperpure Ge detector connected to a Link high count rate pulse processor and a Nuclear Data ND-66 analyser. The detector had a resolution of 2.08 keV (full-width at half-maximum) at the 1332 keV photopeak of 6OCo. The 443 kcV y-ray of 12*l was free from interference and was therefore used for assaying iodine. Microwave Acid Digestion of Samples Microwave acid digestion bombs (Parr Instrument Co.) were used for the dissolution of samples. The bomb contained a chemically inert Teflon sample cup of 45 ml capacity. Details of the development of the sample digestion procedure are given clsewhere.29 Briefly, 200-250 mg of a sample were accurately weighed into a pre-cleaned Teflon sample cup, 5 ml of ultrapure concentrated nitric acid were added, and the mixture was heated for 35 s at a power of 675 W in a microwave oven.The digestion step was repeated after a 20 rnin cooling period, if necessary. This procedure yielded sufficiently complete decomposition of the sample with respect to iodine. The contents of the cup were poured into a pre-cleaned 250 ml beaker containing 1 g of hydrazine sulfate. The cup and its lid were rinsed successively with 3 x 5 ml aliquots of each of a 5% hydrazine sulfate solution and DDW. The washings were added to the sample solution. The resulting solution was diluted to 100 mi, maintaining a final acidity of 0.2 rnol 1-l. Preconcentration of Iodine by Bismuth Sulfide Coprecipitation Details of the development of this method have recently been published.'" Bricfly, it involved the sequential dropwise addition of 1 ml of each of bismuth nitrate and thioacetamide stock solutions to a 100 ml digested sample solution at an acidity of 0.2 rnol I-'.The dark brown precipitate formed was allowed to settle for 20 rnin at room temperature and then filtered through a pre-cleaned Gelman membrane filter under vacuum suction. The precipitate was washed three times with 5 ml aliquots of a 0.2 mol I-' nitric acid solution containing 0 . I% hydrazine sulfate. The filter containing the precipitate was folded, placed in a 1.2 ml polyethylene vial and heat- sealed. The vial was irradiated in an epi-cadmium neutron flux of 1 .0 x 1010 n cm-2 s- for 30 or 60 min and counted for either 30 or 60 rnin after a decay period of I min.Preconcentration of Iodine by Toluene Extraction The digested sample solution was poured into a 250 ml beaker. The sample cup and lid of the microwave digestion bomb were thoroughly rinsed with 2 x 5 ml portions of a 5% hydrazine sulfate solution and subsequently with 2 x 5 ml portions of DDW. The washings were added to the sample solution and the final acidity of the resulting solution was adjusted to between 1 and 2 rnol I-', maintaining a total volume of 30 ml. This solution was transferred into a 125 ml Pyrex separating funnel. Then, 10 ml of toluene and 5 ml of a 10% NaN02 solution were added. Iodine was extracted into the organic phase by shaking on a wrist-action mechanical shaker for 10 min.The organic phase was transferred into another separat- ing funnel. The extraction procedure was repeated three times with 10 ml of toluene and 2 ml of a 10% NaN02 solution. The extraction recovery of iodine was checked by irradiating 1 mi aliquots of the organic phasc after each extraction and calculating the yield of iodine. Preliminary experiments with spiked standard iodine and with 1251 tracer revealed that three extractions were sufficient for the complete recovery of iodine (>99%). The organic phases were combined in a separating funnel. The iodine was reduced to iodide and back-extracted into the aqueous phase by equilibrating with 2 x 10 ml portions of a 5% hydrazine sulfate solution. The aqueous phases containing iodide were combined and diluted to 100 ml, maintaining a final acidity of 0.2 mol I-' with rcspect to nitric acid.Samples containing relatively large amounts of chlorine and bromine were first treated by this toluene cxtraction method to isolate iodine. Then, the bismuth sulfide coprecipitation procedure described above was used to concentrate the iodide further and collect it in a precipitate which is suitable for NAA. The iodine content of the precipitate was measured by irradiating in an epi-cadmium neutron flux of 1 x 1OlO n cm-? s-I for 60 rnin and counting for 60 rnin after a decay period of 1 min. Radiochemical Separation of Iodine by Bismuth Sulfide Coprecipitation About 250 mg of a sample were accurately weighed into a pre- cleaned polyethylene vial and irradiated for 60 min in an integral neutron flux of 1 X 1012 n cm-? s-I.The vial was opened and the sample was transferred into a Teflon sample cup of the microwave digestion bomb. The vial was rinsed three times with 1 ml portions of ultrapure concentrated nitric acid. The irradiated sample was spiked with 100 pI of 1251 tracer solution and digested according to the procedure described under Microwave Acid Digestion of Samples. To the digested sample solution, 2 ml of bismuth nitrate stock solution, 1 ml of ammonium iodide (1 mg ml-I I - ) and 2 ml of thioacetamide stock solution were added sequentially while stirring the solution with a magnetic stirrer. The resulting dark brown precipitate was allowed to settle for 20 min and then filtered through a Gelman membrane filter under vacuum suction. The entire procedure was completed within 50 min from the end of the irradiation. The filter was folded, placed in a new 1.2 ml polyethylene vial and counted for 30 min. The recovery of iodine was checked by measuring the activity of the 1251 tracer. Radiochemical Purification by Palladium Iodide Precipitation Thc sample was digested according to the procedure described under Microwave Acid Digestion o f Samples. This solution was taken through the bismuth sulfide coprecipitation proce- dure. The precipitate was collected and irradiated for 60 rnin in an integral neutron flux of 1 X 1012 n cm-2 s-I. The irradiated precipitate was washed off the filter into a beaker with 5 ml of concentrated nitric acid. The filter was rinsed thoroughly with 4 mol I-' nitric acid and subsequently with 10 ml of a 5% hydrazine sulfate solution. The sample solution was diluted to SO ml with DDW, maintaining a final acidity between 2 and 4 rnol I-'. To this solution, 0.5 ml aliquots of

ISSN:0003-2654    

DOI:10.1039/AN993180125N

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

1248 ANALYST, OCTOBER 1993, VO12. 118 ng ml-l iodide. The iodide comparator standards were prepared by transferring microlitre portions of the iodide standard solution onto pre-cleaned Gelman Sciences GA-6S membrane filters (0.45 pm pore size, 47 mm diameter) placed in pre-cleaned 1.2 ml polyethylene irradiation vials. The comparator standards and samples were prepared to have identical geometry. Reference Materials A number of CRMs and Standard Reference Materials (SRMs) obtained from the IAEA and the National Institute of Standards and Technology (NIST) , respectively, were analysed to evaluate the accuracy of the methods at the low levels of iodine that might be present in some biological and diet samples. The RMs used were: NIST SRM 1571 Orchard Leaves and SRM 1577 Bovine Liver, and IAEA A-11 Milk Powder.H-4 Animal Muscle and H-9 Mixed Human Diet. Irradiation and Counting All samples and comparator standards were irradiated in the Dalhousie University SLOWPOKE-2 research reactor at a maximum integral neutron flux of 1 x 1012 n cm-2 s-1 or a maximum epi-cadmium neutron flux of 1 x lo'* n cm-2 s - I . They were counted on a 25 ml active volume Aptec hyperpure Ge detector connected to a Link high count rate pulse processor and a Nuclear Data ND-66 analyser. The detector had a resolution of 2.08 keV (full-width at half-maximum) at the 1332 keV photopeak of 6OCo. The 443 kcV y-ray of 12*l was free from interference and was therefore used for assaying iodine. Microwave Acid Digestion of Samples Microwave acid digestion bombs (Parr Instrument Co.) were used for the dissolution of samples.The bomb contained a chemically inert Teflon sample cup of 45 ml capacity. Details of the development of the sample digestion procedure are given clsewhere.29 Briefly, 200-250 mg of a sample were accurately weighed into a pre-cleaned Teflon sample cup, 5 ml of ultrapure concentrated nitric acid were added, and the mixture was heated for 35 s at a power of 675 W in a microwave oven. The digestion step was repeated after a 20 rnin cooling period, if necessary. This procedure yielded sufficiently complete decomposition of the sample with respect to iodine. The contents of the cup were poured into a pre-cleaned 250 ml beaker containing 1 g of hydrazine sulfate. The cup and its lid were rinsed successively with 3 x 5 ml aliquots of each of a 5% hydrazine sulfate solution and DDW.The washings were added to the sample solution. The resulting solution was diluted to 100 mi, maintaining a final acidity of 0.2 rnol 1-l. Preconcentration of Iodine by Bismuth Sulfide Coprecipitation Details of the development of this method have recently been published.'" Bricfly, it involved the sequential dropwise addition of 1 ml of each of bismuth nitrate and thioacetamide stock solutions to a 100 ml digested sample solution at an acidity of 0.2 rnol I-'. The dark brown precipitate formed was allowed to settle for 20 rnin at room temperature and then filtered through a pre-cleaned Gelman membrane filter under vacuum suction. The precipitate was washed three times with 5 ml aliquots of a 0.2 mol I-' nitric acid solution containing 0 .I% hydrazine sulfate. The filter containing the precipitate was folded, placed in a 1.2 ml polyethylene vial and heat- sealed. The vial was irradiated in an epi-cadmium neutron flux of 1 .0 x 1010 n cm-2 s- for 30 or 60 min and counted for either 30 or 60 rnin after a decay period of I min. Preconcentration of Iodine by Toluene Extraction The digested sample solution was poured into a 250 ml beaker. The sample cup and lid of the microwave digestion bomb were thoroughly rinsed with 2 x 5 ml portions of a 5% hydrazine sulfate solution and subsequently with 2 x 5 ml portions of DDW. The washings were added to the sample solution and the final acidity of the resulting solution was adjusted to between 1 and 2 rnol I-', maintaining a total volume of 30 ml.This solution was transferred into a 125 ml Pyrex separating funnel. Then, 10 ml of toluene and 5 ml of a 10% NaN02 solution were added. Iodine was extracted into the organic phase by shaking on a wrist-action mechanical shaker for 10 min. The organic phase was transferred into another separat- ing funnel. The extraction procedure was repeated three times with 10 ml of toluene and 2 ml of a 10% NaN02 solution. The extraction recovery of iodine was checked by irradiating 1 mi aliquots of the organic phasc after each extraction and calculating the yield of iodine. Preliminary experiments with spiked standard iodine and with 1251 tracer revealed that three extractions were sufficient for the complete recovery of iodine (>99%).The organic phases were combined in a separating funnel. The iodine was reduced to iodide and back-extracted into the aqueous phase by equilibrating with 2 x 10 ml portions of a 5% hydrazine sulfate solution. The aqueous phases containing iodide were combined and diluted to 100 ml, maintaining a final acidity of 0.2 mol I-' with rcspect to nitric acid. Samples containing relatively large amounts of chlorine and bromine were first treated by this toluene cxtraction method to isolate iodine. Then, the bismuth sulfide coprecipitation procedure described above was used to concentrate the iodide further and collect it in a precipitate which is suitable for NAA. The iodine content of the precipitate was measured by irradiating in an epi-cadmium neutron flux of 1 x 1OlO n cm-? s-I for 60 rnin and counting for 60 rnin after a decay period of 1 min.Radiochemical Separation of Iodine by Bismuth Sulfide Coprecipitation About 250 mg of a sample were accurately weighed into a pre- cleaned polyethylene vial and irradiated for 60 min in an integral neutron flux of 1 X 1012 n cm-? s-I. The vial was opened and the sample was transferred into a Teflon sample cup of the microwave digestion bomb. The vial was rinsed three times with 1 ml portions of ultrapure concentrated nitric acid. The irradiated sample was spiked with 100 pI of 1251 tracer solution and digested according to the procedure described under Microwave Acid Digestion of Samples. To the digested sample solution, 2 ml of bismuth nitrate stock solution, 1 ml of ammonium iodide (1 mg ml-I I - ) and 2 ml of thioacetamide stock solution were added sequentially while stirring the solution with a magnetic stirrer.The resulting dark brown precipitate was allowed to settle for 20 min and then filtered through a Gelman membrane filter under vacuum suction. The entire procedure was completed within 50 min from the end of the irradiation. The filter was folded, placed in a new 1.2 ml polyethylene vial and counted for 30 min. The recovery of iodine was checked by measuring the activity of the 1251 tracer. Radiochemical Purification by Palladium Iodide Precipitation Thc sample was digested according to the procedure described under Microwave Acid Digestion o f Samples. This solution was taken through the bismuth sulfide coprecipitation proce- dure. The precipitate was collected and irradiated for 60 rnin in an integral neutron flux of 1 X 1012 n cm-2 s-I. The irradiated precipitate was washed off the filter into a beaker with 5 ml of concentrated nitric acid. The filter was rinsed thoroughly with 4 mol I-' nitric acid and subsequently with 10 ml of a 5% hydrazine sulfate solution. The sample solution was diluted to SO ml with DDW, maintaining a final acidity between 2 and 4 rnol I-'. To this solution, 0.5 ml aliquots of

ISSN:0003-2654    

DOI:10.1039/AN993180127N

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

1248 ANALYST, OCTOBER 1993, VO12. 118 ng ml-l iodide. The iodide comparator standards were prepared by transferring microlitre portions of the iodide standard solution onto pre-cleaned Gelman Sciences GA-6S membrane filters (0.45 pm pore size, 47 mm diameter) placed in pre-cleaned 1.2 ml polyethylene irradiation vials. The comparator standards and samples were prepared to have identical geometry. Reference Materials A number of CRMs and Standard Reference Materials (SRMs) obtained from the IAEA and the National Institute of Standards and Technology (NIST) , respectively, were analysed to evaluate the accuracy of the methods at the low levels of iodine that might be present in some biological and diet samples. The RMs used were: NIST SRM 1571 Orchard Leaves and SRM 1577 Bovine Liver, and IAEA A-11 Milk Powder.H-4 Animal Muscle and H-9 Mixed Human Diet. Irradiation and Counting All samples and comparator standards were irradiated in the Dalhousie University SLOWPOKE-2 research reactor at a maximum integral neutron flux of 1 x 1012 n cm-2 s-1 or a maximum epi-cadmium neutron flux of 1 x lo'* n cm-2 s - I . They were counted on a 25 ml active volume Aptec hyperpure Ge detector connected to a Link high count rate pulse processor and a Nuclear Data ND-66 analyser. The detector had a resolution of 2.08 keV (full-width at half-maximum) at the 1332 keV photopeak of 6OCo. The 443 kcV y-ray of 12*l was free from interference and was therefore used for assaying iodine. Microwave Acid Digestion of Samples Microwave acid digestion bombs (Parr Instrument Co.) were used for the dissolution of samples.The bomb contained a chemically inert Teflon sample cup of 45 ml capacity. Details of the development of the sample digestion procedure are given clsewhere.29 Briefly, 200-250 mg of a sample were accurately weighed into a pre-cleaned Teflon sample cup, 5 ml of ultrapure concentrated nitric acid were added, and the mixture was heated for 35 s at a power of 675 W in a microwave oven. The digestion step was repeated after a 20 rnin cooling period, if necessary. This procedure yielded sufficiently complete decomposition of the sample with respect to iodine. The contents of the cup were poured into a pre-cleaned 250 ml beaker containing 1 g of hydrazine sulfate. The cup and its lid were rinsed successively with 3 x 5 ml aliquots of each of a 5% hydrazine sulfate solution and DDW.The washings were added to the sample solution. The resulting solution was diluted to 100 mi, maintaining a final acidity of 0.2 rnol 1-l. Preconcentration of Iodine by Bismuth Sulfide Coprecipitation Details of the development of this method have recently been published.'" Bricfly, it involved the sequential dropwise addition of 1 ml of each of bismuth nitrate and thioacetamide stock solutions to a 100 ml digested sample solution at an acidity of 0.2 rnol I-'. The dark brown precipitate formed was allowed to settle for 20 rnin at room temperature and then filtered through a pre-cleaned Gelman membrane filter under vacuum suction. The precipitate was washed three times with 5 ml aliquots of a 0.2 mol I-' nitric acid solution containing 0 .I% hydrazine sulfate. The filter containing the precipitate was folded, placed in a 1.2 ml polyethylene vial and heat- sealed. The vial was irradiated in an epi-cadmium neutron flux of 1 .0 x 1010 n cm-2 s- for 30 or 60 min and counted for either 30 or 60 rnin after a decay period of I min. Preconcentration of Iodine by Toluene Extraction The digested sample solution was poured into a 250 ml beaker. The sample cup and lid of the microwave digestion bomb were thoroughly rinsed with 2 x 5 ml portions of a 5% hydrazine sulfate solution and subsequently with 2 x 5 ml portions of DDW. The washings were added to the sample solution and the final acidity of the resulting solution was adjusted to between 1 and 2 rnol I-', maintaining a total volume of 30 ml.This solution was transferred into a 125 ml Pyrex separating funnel. Then, 10 ml of toluene and 5 ml of a 10% NaN02 solution were added. Iodine was extracted into the organic phase by shaking on a wrist-action mechanical shaker for 10 min. The organic phase was transferred into another separat- ing funnel. The extraction procedure was repeated three times with 10 ml of toluene and 2 ml of a 10% NaN02 solution. The extraction recovery of iodine was checked by irradiating 1 mi aliquots of the organic phasc after each extraction and calculating the yield of iodine. Preliminary experiments with spiked standard iodine and with 1251 tracer revealed that three extractions were sufficient for the complete recovery of iodine (>99%).The organic phases were combined in a separating funnel. The iodine was reduced to iodide and back-extracted into the aqueous phase by equilibrating with 2 x 10 ml portions of a 5% hydrazine sulfate solution. The aqueous phases containing iodide were combined and diluted to 100 ml, maintaining a final acidity of 0.2 mol I-' with rcspect to nitric acid. Samples containing relatively large amounts of chlorine and bromine were first treated by this toluene cxtraction method to isolate iodine. Then, the bismuth sulfide coprecipitation procedure described above was used to concentrate the iodide further and collect it in a precipitate which is suitable for NAA. The iodine content of the precipitate was measured by irradiating in an epi-cadmium neutron flux of 1 x 1OlO n cm-? s-I for 60 rnin and counting for 60 rnin after a decay period of 1 min.Radiochemical Separation of Iodine by Bismuth Sulfide Coprecipitation About 250 mg of a sample were accurately weighed into a pre- cleaned polyethylene vial and irradiated for 60 min in an integral neutron flux of 1 X 1012 n cm-? s-I. The vial was opened and the sample was transferred into a Teflon sample cup of the microwave digestion bomb. The vial was rinsed three times with 1 ml portions of ultrapure concentrated nitric acid. The irradiated sample was spiked with 100 pI of 1251 tracer solution and digested according to the procedure described under Microwave Acid Digestion of Samples. To the digested sample solution, 2 ml of bismuth nitrate stock solution, 1 ml of ammonium iodide (1 mg ml-I I - ) and 2 ml of thioacetamide stock solution were added sequentially while stirring the solution with a magnetic stirrer.The resulting dark brown precipitate was allowed to settle for 20 min and then filtered through a Gelman membrane filter under vacuum suction. The entire procedure was completed within 50 min from the end of the irradiation. The filter was folded, placed in a new 1.2 ml polyethylene vial and counted for 30 min. The recovery of iodine was checked by measuring the activity of the 1251 tracer. Radiochemical Purification by Palladium Iodide Precipitation Thc sample was digested according to the procedure described under Microwave Acid Digestion o f Samples. This solution was taken through the bismuth sulfide coprecipitation proce- dure. The precipitate was collected and irradiated for 60 rnin in an integral neutron flux of 1 X 1012 n cm-2 s-I. The irradiated precipitate was washed off the filter into a beaker with 5 ml of concentrated nitric acid. The filter was rinsed thoroughly with 4 mol I-' nitric acid and subsequently with 10 ml of a 5% hydrazine sulfate solution. The sample solution was diluted to SO ml with DDW, maintaining a final acidity between 2 and 4 rnol I-'. To this solution, 0.5 ml aliquots of

ISSN:0003-2654    

DOI:10.1039/AN993180128N

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, OCTOBER 1993, VOL. 118 123s Characterization of Planar Concentration Gradients in a Sequential- injection System for Cell-perfusion Studies Cy H. Pollema and Jaromir RBfiCka" Department of Chemistry, University of Washington, Seattle, WA 98195, USA This paper describes the characterization of a perfusion chamber that is coupled with a sequential-injection system and is being designed for live-cell perfusion. The apparatus consists of a multi-port valve, a peristaltic pump, a perfusion chamber and an epifluorescence microscope. The entire system is computer controlled and temperature regulated. The parameters discussed are the concentration-time profiles with regard t o the volume of reagent used and the position of the cell i n the perfusion chamber. Other parameters discussed include the stopped-flow compliance, reproducibility and symmetry of the concentration gradients formed.The system is shown to be suitable for two modes of perfusion; the first in which all cells are exposed to the same concentration of reagent, and the second in which cells are exposed to a gradient of concentrations. All characterization is performed with use of bulk fluorescein as a tracer, and a correlation is made between the bulk flow and the response within the cellular environment by using 5-[N-(octadecanoyl)amino]fluorescein. Keywords: Flow injection; sequential injection; perfusion; live cell; planar concentration gradient Currently available cellular probes permit the measurement of physiologically relevant properties such as specific cellular component staining, measurement of intracellular calcium level, pH, membrane potential and a host of other cellular functions and structures1 by digital-imaging microscopy.The study of cellular changes requires the precise control of several experimental variables, including a probe to elicit the response, a detection system with adequate speed and sensitivity to monitor the change, and a method of changing the cellular environment to which the response under study occurs. The technology of microscopy is advancing rapidly, with higher resolution, low-light level cameras, faster confocal systems, and more computing power for the collection and storage of data. However, the control of the cellular environment often involves manual reagent introduction such as pipetting into the stagnant solution contained in a Petri dish.Automated cell-perfusion techniques have been intro- duced and are outlined in a previous study.2 Briefly, in order to determine the response to a change in the perfusing medium, the time for wash-out must be negligible with respect to the dynamics of the response being measured.3 This places a high priority on fast wash-out with little or no unswept volumes. We are introducing a simple system capable of a wide variety of protocols, with an emphasis on the flow characteristics, and based on flow-injection principles. The sequential-injection analysis (SIA) system [Fig. l(a)] consists of a bidirectional pump, a holding coil (HC), a multiposition valve QvlPV), a transfer line (TL) and a fountain cell (FC).Adherent cells are attached to a circular cover-slip, which is placed in the fountain cell for perfusion and monitoring. The function of this system is to provide the cells with a perfusing buffer at controlled temperature and flow rate (typically, 1 ml min-l). This will provide the ability to expose cells to impulses of a reagent of a defined concentration for a well-defined period. Computer control of the system allows the automated introduction of a sequence of reagents and wash solutions to cells in the chamber in a pre-programmed fashion. In this paper the perfusion system is characterized by exploring the bulk flow behaviour and its relationship to the stimulation of cells adhered within the perfusion chamber. Experimental The SIA system consisted of a Valco ten-position dead-stop selector valve (Valco Instruments, Houston, TX, USA) and * To whom correspondence should be addressed.an Alitea Type C-4V peristaltic pump (Alitea USA, Medina, WA, USA). The holding coil connecting the pump and valve was 0.8 mm i.d. poly(tetrafluoroethy1ene) (PTFE) coiled with a total calculated volume of 800 PI. Larger-diameter tubing was used on the holding coil to help prevent out-gassing during the aspiration of reagents. All other tubing was 0.5 mm i.d. PTFE. The peristaltic tubing, Masterflex (Cole-Parmer, Niles, IL, USA) No. 13, was coated on the outside with silicone oil and removed from the pump, when not in use, to minimize wear. The perfusion chamber used was of fountain cell design,4 and was constructed as previously described, and connected to the SIA systems via a 30 p1 (0.5 mm i.d.) transfer line, which was tightly knotted just before the inlet to randomize the flow.The fountain cell contained a Plexiglas insert with a collection u Pump V ' I a-D R2 Flow direction D w Fig. 1 ( a ) Sequential-injection system consisting of a bidirectional peristaltic pump, a holding coil (HC), multiposition valve (MPV), with rea ents (R) clustered at different port positions, and a transfer line (TLf connecting the valve to the fountain cell (FC). ( b ) and (c) Illustrations of the perfusion chamber showing side and overhead views, respectively; the overhead view includes illustrations of the fields observed (A-D) covering a radius from 2 to 5 mm, respectively, d being 0.5 mm and h being varied from 0.38 mm to 1.14 mm.Dotted area in inset to (b) and central shaded area in ( c ) show region of turbulence (see text for details)1236 ANALYST, OCTOBER 1993, VOL. 118 ring of radius 6.4 mm. The ring was 3.2 mm wide and 3.2 mm deep, giving it a total volume of 514 pl. The outlet from the collection ring was 0.8 mm i.d. PTFE tubing with a short (2 cm) length of 0.3 mm i.d. PTFE tubing placed downstream as a flow restrictor. This served to maintain the pressure in the fountain cell and prevent the formation of bubbles during the pressure drop associated with the radial expansion. The flow path was defined by a 381 pm PTFE spacer (Small Parts, Miami Lakes, FL, USA), yielding a detection region volume of 49 pl. The upper surface of the detection region consisted of a 25 mm round No.1 cover glass, which, in cell studies, would be coated with the cell monolayer. The cover glass was held in place with a threaded ring attached to the outer body of the fountain cell, and was easily exchanged. The detector was a Zeiss Universal microscope (Carl Zeiss, Oberkochen, Germany) equippcd with a Type 111-RS epiflu- oresccnce attachment and 50 W mercury-arc source. The source was shuttered by using a Uniblitz Model T132 controller and shutter (Vincent Associates, Rochester, NY, USA). Fluorescence signals were detected by either a Nikon PI photomultiplier tube (Nikon, Tokyo, Japan) or a COHU 6500 camera (Cohu Inc., San Diego, CA, USA) linked to an Olympus 90 mm macro lens. Photomultiplier tube detection of SIA zones involved use of a 25X planapochromatic objective (normal aperture 0.45), with a detection region of 0.345 x 0.436 mm.The video imaging of zones was accomplished by removing the objective lens and using the zoom lens for focusing. The excitation light was optimized experimentally. While uniform illumination was not obtained, this is normal with an arc source and can be compensated for by flat-field correction when quantitative results are desired. The excita- tion and emission wavelengths were defined by a dichroic mirror, allowing 450-490 nm excitation and 520 nm long-pass emission. Thermostatically controlling the system for cell perfusion work involved two separate areas, one for the perfusion buffer and reagents, and one for the stage and perfusion chamber. The perfusion buffer was kept in a water-bath at 37 "C, with the holding coil and reagents warmed by using the heated recirculating water.The reagents were kept in a smaller water- bath that was heated by using the recirculating water from the bath containing the perfusion buffer. It was found that the smaller bath maintained a temperature of approximately 35 "C, which was adequate, as these small volumes would be brought up to 37 "C when merged with the carrier and sent into the perfusion chamber. The holding coil was wrapped with similar copper tubing to help maintain the temperature of the liquids within the SIA system. The stage and perfusion chamber wcrc thermostatically controlled with use of an air- curtain incubator controlled via an Omega CN76000 pro- portional controller (Omega, Stamford, CT, USA).The temperature probe was an Omega Type 860 RTD placed directly on the cover glass with the controller indicating a temperature of 37 k 0.2 "C during experiments. Control of the SIA system and data collection from the photomultiplier tube were carried out with use of an RTD ADA1100 interface board (Real Time Devices, State College, PA, USA) in a Comtrade (City of Industry, CA, USA) 80486 computer. The data collection and control software was Atlantis (Lakeshore Technology, Chicago, IL, USA). Video imaging involved use of a Quickcapture frame grabber card (Data Translation, Marlboro, MA, USA) in a Macintosh IIci, with the image collection and manipulation controlled by National Institute of Health, USA, image system. Characterization of the SIA system was performed using 1 pg 1-1 fluorescein (Sigma, St.Louis, MO, USA) diluted in 0.01 mol I-' sodium borate buffer. The carrier was also 0.01 mol I-' sodium borate buffer and was typically used at 1 ml min- unless otherwise stated. To ensure the linearity of the response, four different dilutions (1.04.1 pg I-') were tested, using 85 p1 of fluorescein. Over this range, the response was linear. In the experiments carried out the aspirated volume was varied over the range 17-340 p1. For the cell studies, a Krebs-Ringer buffer (KRR), with MEM essential and non- essential amino acids (Gibco BRL), 1% bovine serum albumin, 20 mol I- I N'-(2-hydroxyethyl)piperazine-N-ethane- sulfonic acid and 5 mmol I-' glucose, was perfused at a flow rate of 1 ml min-I.The pH-sensitive probe 5-[N-(octadc- canoyl)amino]fluorescein(C18Fl) (Molecular Probes, Eugene, OR, USA) was used to probe the relationship between bulk flow and cell stimulation. The probe was dissolved in ethanol to form a stock solution of 2 mg ml-I. The stock solution was then diluted in the KRB to a final concentration of 10 pg ml-', and the pH of a portion of the buffer for bulk experiments was adjusted to 4. For cell studies, the cells were incubated for 10 min with the pH 7 KRB containing the probe, then perfused with medium free of the probe. The volume of pH 4 buffer was 85 pl. The cell line used for this work was a rat insulinoma cell (RIN-5AH) . Results and Discussion System Considerations The design of a sequential-injectiori system is based on a set of parameters, which are related to its physical configuration and to the concentration and volume of the material injected into the system.Starting with the configuration, the over-all dispersion in the system is the sum of variances s2, which express the individual contribution of system components S2TOT = S2Mp" + S2Hc + s2TL + S2FC (1) where TOT refers to the total system while the other subscripts are shown in Fig. l(a). Recalling that one of the aims of this design is to allow staining of all cells by the same reagent concentration (no concentration gradient), then .+,(. << s * ~ ( , ~ . Furthermore, in order to minimize the volume of solution to be used, the dispersion of the components of the SIA system also needs to be minimized. Some important considerations include the volume (i.e., length, diamctcr and ultimately s 2 ) of the transfer line and of the holding coil, and the internal volume of the valve. The configuration of the multiposition valve used in this study is such that a common ring is internal to the valve, which has a volume of approximately 10 pl; this term could dominate dispersion of some systems, making the ~ 2 ~ ~ " an important term.However, with a given valve, there are other important parameters. As each injected element moves through a section of the holding coil twice, the tube diameter can be selected in such a way as to dominate the over-all variance ( s * , ~ ~ ) ; in addition, the transfer line to the perfusion chamber also plays a crucial role. As the aim of this study is a system with low dispersion, the i.d.of the holding coil was 0.8 mm, while the i.d. of the transfer line was 0.5 mm and its length was 15 cm. These dimensions are a result of practical considerations. Use of smaller- diameter tubing tends to lead to clogging and pressure problems. The holding coil i.d. is slightly larger to prevent a high vacuum, which would lead to the formation of bubbles. To verify that the system fulfills the requirements of having low dispersion, in which thc contribution of the perfusion chamber over a given region to dispersion can be practically neglected, the depth of the chamber was varied. By using three different channel depths, the over-all dispersion of the system was calculated. This is reasonably well approximated by treating the system as a single stirred-tank models in which the dispersion coefficient D becomes a function of the injected volume as (2) D-1 = c/q, = e-'.f The dispersion coefficient is related to the maximum concentration that passes the point of observation ( c ) and the initial concentration (c,)).The dispersion of a system can also be related to the injected reagent volume, which results in a signal equal to half the signal produced by undiluted reagent ( c = 0 . 5 ~ ~ ~ ) ; this volume will be referred to as the R1,2. ThisANALYST, OCTOBER 1993. VOI,. I18 1237 volume provides a useful relationship with the dispersion of a system as low R1/2 values indicate low dispersion. The value of RIl2 can be established by injecting increasing sample volumeso and plotting the aspirated volume versus [-In (1 - c/cO)].The resulting line yields the R,,? volume when [-In (1 - c/cO)] equals 0.693. Channel depths [h in Fig. l(b)] being varied to 0.38,0.76 and 1.14 mm yielded RlI2 volumes of 33, 34 and 44 PI, respectively. Hence, the contribution of the fountain cell to the over-all dispersion of this system is negligible as large changes in the volume of the fountain cell result in small changes in the Rll2 and, therefore, the over-all system variance. Radial Flow The fountain cell [Fig. l ( h ) and (c)] exploits the symmetry of the radial flow pattern formed by a laminar stream of fluid impinging perpendicularly on a planar surface. The fluid quickly translates into radial flow, with negligible unswept volume in the transition region.It was the large viewing area and fluid flow properties that made a radial perfusion chamber design appealing. However, introduction of a radial-flow perfusion chamber requires a brief discussion of relevant previous work involving use of similar chambers. The import- ant parameters of radial flow between confined boundaries have been identified in studies on air at incompressible speeds.7 These conclusions should also describe the character- istics of non-compressible liquids. The pressure at differeirt radial locations and the flow velocity were described under conditions of either laminar or turbulent flow. The equation for the mean velocity in the radial direction, assuming laminar flow conditions, is <u> = (2 (2nrh)-' ( 3 ) where Q is the channel inlet volume flow, Y is the radial distance from the centre of the inlet, and h is the height or depth of the channel.It was also determined from this study that transition from turbulent to laminar flow occurred at a Rcynold's number of 2000 in radial flow, which is approxi- mately equal to that for flow in two-dimensional channels and circular pipes. The perfusion system being characterized operates in a range of Reynold's numbers from 5.4 at 1 mm from the inlet to 1.1 at 5 mm from the inlet. Radial flow has been used for the measurement of cell adhesion.* A study by Fowler and McKay8 exploited the change in cross-sectional area with increasing radius, which causes the linear flow velocity and hence the surface shear force to decrease linearly along the radius of the chamber.The strength of cell attachment was evaluated by measuring the critical shear radius, which is the distance from the inner edge of attached cells to the central inlet. From this the minimum distraction force, F, is shown to be F = 3 Q pk (n rhZ)-' (4) where Q is the flow rate of liquid emerging from the inlet (I min-I), p is the viscosity (cP), Y is the critical shear radius (mm), h is the distance between the cover-slip and the outlet disc (mm), and k is a constant (16.7), which allows F to be determined in N m-? (Pa).g More recently, radial flow has been used in an extensive study of the cell adhesion and detachment by using a radial-flow detachment appar- atus.h,lO.~' In this work, coated latex beads were used as model cells to evaluate the kinetics of adhesion by measuring the critical shear radius.The effects of ligand and receptor densities and the influence of pH and ionic strength of the medium were addressed. The relevance of these publications to this work is three- fold. First, they show that the flow rate within the fountain cell decreases linearly as the distance travelled from the inlet ( Y ) increases and that the pressure at any radius is inversely proportional to the fourth power of channel depth. Next, it has been demonstrated that cells remained adherent during a 3 h period at a flow rate of 500 ml min-' in a shearing apparatus having a channel depth of 1 mm. This indicates that no cells will be inadvertently detached during a sequential- injection experiment, as it is proposed here to use flow rates 500 times lower.Lastly, although radial flow chambers have been used for shear stress studies for some time, their use for cytochemical studies in conjunction with sequential injection has not been considered. In order to do so effectively, the behaviour of the concentration gradients created by sequen- tial injection in radial flow between confined boundaries needs to be studied. Also, for the effective use of this system in the study of cellular processes, a clear understanding of the flow properties is necessary. This will aid in defining the concentra- tions and contact times for which adhered cells are exposed to a selected reagent. System Characterization The characterization focused on the concentration-time profiles as observed in the fountain cell.However, it should be kept in mind that it is the geometry of the over-all system which determines the flow pattern of the concentration gradient that reaches the inlet of the fountain cell. Within the cell itself, the first important parameter to consider is the 'separation bubble' formed as the flow transitions from thc inlet into the radial chamber. [See Fig. l(6) dotted area of detail and Fig. l(c) shaded area in centre.] This transition region is formed as the flow leaves the inlet, separates from the inlet corner and then re-attaches to the back wall at some radius from the inlet. If the channel is sufficiently deep, the re- attachment will no longer occur, and a radial wall jet will form. This flow pattern causes unswept volumes that will increase the wash-out time of the chamber.I n this study, the presence of an annular separation bubble was qualitatively determined with use of 4.5 pm Fluoresbrite beads (Polysciences, Warr- ington, PA, USA), while the perfusion chamber thickness was varied by inserting additional YTFE spacers. At a depth o f 0.76 mm, which is twice the value proposed for this study, the flow reconnected approximately 0.8 mm from the centre. This region was easily identified as beads held within the separation bubble appeared to How towards the centre, while those outside flowed radially outward. Doubling this depth to 1.52 mm increased the distance for reconnection to approximately 1.6 mm. Increasing further to 2.28 mm, the reconnection was not visible. Therefore, further work was conducted with the 0.38 mm spacer, which confined the bubble to the area inside the end of the PTFE tubing and afforded well swept areas, avoiding the wall-jet effect. Mapping of the surface was also limited to the area outside of a 2 mm radius to avoid this uncharacterizcd region.The perfusion chamber can be operated in two different modes based on the aspirated volume used: (1) all cells are treated the same (uniform reagent contact), or (2) cells are treated differentially based on their position relative to the inlet (gradient reagent contact). Conditions required for each of these catagories were asccrtained by microscopic mapping of the fountain cell area, and measuring dispersion (D) values at four points A, B, C and I1 [Fig. l(c)], which were radially displaced 2 , 3 , 4 and 5 mm from the central inlet.By selecting 25X magnification, the observation area at each point was approximately 0.150 mm2. Uniform Reagent Contact By injecting 340 pl of fluorescein and monitoring the zone passage through the fountain cell at continuous flow, four traces were obtained (Fig. 2)' which show remarkable similarity in peak heights, variances and shapes. As one would expect, the peak maxima shift to longer times as the position of the observation spot moves away from the inlet. Surpris- ingly, however, the peak width does not increase as the zone moves outwards, and as the linear flow velocity is decreasing1238 ANALYST, OCTOBER 1993, VOL. 118 as a function of the radius [eqn. ( 3 ) ] , the zone appears to be focusing in the forward direction.This can be explained by the fact that a fixed volume of reagent forms a ring, which, as it expands outward, must also thin in bandwidth to occupy still the same volume; spreading is small owing to the minimal wall effects in the chamber. The over-all beneficial result is that all cells regardless of their radial distance from the inlet will be perfused by the same reagent concentration (peak height) for the same period of time (peak width), although not at the same time (as the positions of peak maxima are slightly increasing towards longer times). A summary of the mapping experiments is shown in Fig. 3, from which it follows that, by injecting a minimum of 170 pl (approximately 4R1I2), D = 1 is obtained throughout the entire area of the fountain cell.As in classical flow injection, injecting reagent volumes beyond 4R1, is a waste of reagent as it cannot increase the concentration of reagent beyond co. It should be realized that there is no need to reach the maximum reagent concentration (co) to provide well-defined reagent concentrations and contact times. The D value, once established, is a constant of the system for a given flow rate and component configuration. Hence, injection of 170 p1 of reagent (Fig. 3) into the present system is the best choice for homogeneous perfusion of the entire area. However, 85 p1 (Fig. 4) could prove suitable if the reagent is expensive and if the concentration of reagent contacting the cells [62-76% of the originally injected concentration (co)] is deemed sufficient 0 10 20 30 40 50 60 Time/s Fig.2 locations from the centre: A, 2; B, 3; C, 4; and D, 5 mm Concentration-time profiles for 340 pl zones at different radial 1 2 3 4 5 Rad ius/m m Fig. 3 Plot of radius versus dispersion coefficient for various aspiratcd volumes: A. 17; B, 85; C, 170; D, 255; and E, 340 pl This injected volume while it does yield a slight gradient, uses considerably less reagent and provides a contact time of less than 10 s at continous flow. For longer contact times the flow can be stopped at the isoconcentration point (Fig. 4, I), when all cells, regardless of their distance from the inlet, are exposed to the same reagent concentration. Experiments have been run to determine if extended stopped flow is reliable when using this system. An 85 p1 zone of fluorescein was injected into the chamber and the flow was stopped.A location 2 mm from the centre was illuminated in 750 ms impulses every 15 s to minimize photobleaching. The data collected showed no change in signal with stop periods extending up to 30 mins, indicating that extended stopped- flow contact times will allow cell contact with a constant concentration of perfusing solution. A certain minimum volume is always required to obtain these conditions. How- ever, by minimizing all the dispersing components of the system, this volume can remain fairly small. Note that this SIA system then allows for the automated selection of many different reagents, which can be reproducibly introduced and removed from the chamber over a wide range of times. During these times, cells are exposed minimally to a shear force due to the flow within the chamber, which ranges from over 5 to less than 1 x N ~ m - ~ for the given conditions.This shear range may cause shear response in some cell lines and should, therefore, be evaluated for each cell line used. Very short contact times can be obtained by flow reversal, which also allows formation of nearly square-shaped concen- tration impulses. Hence, by injecting the reagent, letting only the leading edge of the dispersed zone enter the fountain cell, and reversing the flow to withdraw the zone quickly, contact times of 100 ms can be obtained. Once withdrawn, the reagent can be aspirated into the holding coil from where it can flow to waste at an auxiliary port, or it can be returned to contact the cells again.The difficulty with the latter approach is that each flow reversal adds dispersion to the zone, and changes its character. The advantages would be in the savings of reagents through its ‘recycling’ and the speed with which the reagent could be applied and withdrawn. Gradient Reagent Contact If concentration gradients are desired, there are two ways to obtain these conditions. One is to work with small volumes that will disperse noticeably across the chamber, and the other is to stop the flow as the leading edge of the reagent zone arrives into the chamber. By decreasing the volume of the injected zone to 85 p1 of fluorescein while under the conditions of the previous experiment, a pattern is observed (Fig. 4) whereby the peak height decreases with the increase of the 0 10 20 30 40 50 60 Ti me/s Fig.4 Concentration-time profiles for 85 p1 zones at different radial locations from the centre: A, 2; B, 3; C, 4; and D, 5 mm. Also indicated is the isoconcentration point (I)1238 ANALYST, OCTOBER 1993, VOL. 118 as a function of the radius [eqn. ( 3 ) ] , the zone appears to be focusing in the forward direction. This can be explained by the fact that a fixed volume of reagent forms a ring, which, as it expands outward, must also thin in bandwidth to occupy still the same volume; spreading is small owing to the minimal wall effects in the chamber. The over-all beneficial result is that all cells regardless of their radial distance from the inlet will be perfused by the same reagent concentration (peak height) for the same period of time (peak width), although not at the same time (as the positions of peak maxima are slightly increasing towards longer times).A summary of the mapping experiments is shown in Fig. 3, from which it follows that, by injecting a minimum of 170 pl (approximately 4R1I2), D = 1 is obtained throughout the entire area of the fountain cell. As in classical flow injection, injecting reagent volumes beyond 4R1, is a waste of reagent as it cannot increase the concentration of reagent beyond co. It should be realized that there is no need to reach the maximum reagent concentration (co) to provide well-defined reagent concentrations and contact times. The D value, once established, is a constant of the system for a given flow rate and component configuration.Hence, injection of 170 p1 of reagent (Fig. 3) into the present system is the best choice for homogeneous perfusion of the entire area. However, 85 p1 (Fig. 4) could prove suitable if the reagent is expensive and if the concentration of reagent contacting the cells [62-76% of the originally injected concentration (co)] is deemed sufficient 0 10 20 30 40 50 60 Time/s Fig. 2 locations from the centre: A, 2; B, 3; C, 4; and D, 5 mm Concentration-time profiles for 340 pl zones at different radial 1 2 3 4 5 Rad ius/m m Fig. 3 Plot of radius versus dispersion coefficient for various aspiratcd volumes: A. 17; B, 85; C, 170; D, 255; and E, 340 pl This injected volume while it does yield a slight gradient, uses considerably less reagent and provides a contact time of less than 10 s at continous flow.For longer contact times the flow can be stopped at the isoconcentration point (Fig. 4, I), when all cells, regardless of their distance from the inlet, are exposed to the same reagent concentration. Experiments have been run to determine if extended stopped flow is reliable when using this system. An 85 p1 zone of fluorescein was injected into the chamber and the flow was stopped. A location 2 mm from the centre was illuminated in 750 ms impulses every 15 s to minimize photobleaching. The data collected showed no change in signal with stop periods extending up to 30 mins, indicating that extended stopped- flow contact times will allow cell contact with a constant concentration of perfusing solution. A certain minimum volume is always required to obtain these conditions.How- ever, by minimizing all the dispersing components of the system, this volume can remain fairly small. Note that this SIA system then allows for the automated selection of many different reagents, which can be reproducibly introduced and removed from the chamber over a wide range of times. During these times, cells are exposed minimally to a shear force due to the flow within the chamber, which ranges from over 5 to less than 1 x N ~ m - ~ for the given conditions. This shear range may cause shear response in some cell lines and should, therefore, be evaluated for each cell line used. Very short contact times can be obtained by flow reversal, which also allows formation of nearly square-shaped concen- tration impulses. Hence, by injecting the reagent, letting only the leading edge of the dispersed zone enter the fountain cell, and reversing the flow to withdraw the zone quickly, contact times of 100 ms can be obtained.Once withdrawn, the reagent can be aspirated into the holding coil from where it can flow to waste at an auxiliary port, or it can be returned to contact the cells again. The difficulty with the latter approach is that each flow reversal adds dispersion to the zone, and changes its character. The advantages would be in the savings of reagents through its ‘recycling’ and the speed with which the reagent could be applied and withdrawn. Gradient Reagent Contact If concentration gradients are desired, there are two ways to obtain these conditions.One is to work with small volumes that will disperse noticeably across the chamber, and the other is to stop the flow as the leading edge of the reagent zone arrives into the chamber. By decreasing the volume of the injected zone to 85 p1 of fluorescein while under the conditions of the previous experiment, a pattern is observed (Fig. 4) whereby the peak height decreases with the increase of the 0 10 20 30 40 50 60 Ti me/s Fig. 4 Concentration-time profiles for 85 p1 zones at different radial locations from the centre: A, 2; B, 3; C, 4; and D, 5 mm. Also indicated is the isoconcentration point (I)I240 bulk flow and cell response at the leading edge of the injected zone over the range covered, Liz., 2 [Fig. 6(a)], 1 [Fig. 6(h)] and 0.5 ml min-1 [Fig.6(c)J. The oscillations seen in the figures are due to the pulsatile flow generated by the peristaltic pumping. While these figures do indicate that the behaviour of the bulk flow at the leading edge is almost identical with that contacting the cells, this could not have been assumed apriori. The trailing edge of the peaks differs more significantly; however, we believe this is due mainly to photobleaching. The difference in photobleaching is seen because the bulk signal results from new fluorophores constantly streaming by, while on the cells there is no renewal possible; hence, photobleach- ing would be seen more in the cell experiment. This idea is supported in Fig. 6 ( 4 , which shows the results from a similar experiment that has been carried out on C18F1-loaded cells with the light source on continuously (solid line) or pulsed ( x).Both traces are from the same group of cells exposed to repeated impulses; with the pulsed source the signal nearly returns to the baseline. Further work is underway in our laboratory to understand better the interaction of the fluid flow environment of the cell when exposed to impulses of a stimulant. We believe that a clear idea o f how a reagent contacts and leaves a cell could provide much more infor- mation about cellular responses than is currently available. It allows the study of both the cell stimulation and recovery in a well-controlled environment. ‘The authors thank Ake Lernmark for his many helpful discussions and for providing the materials needed for the cell study. We also thank Gary Christian and Kurt Scudder for all ANALYST, OCTOBER 1093. VOL. 1 I8 their assistance. The financial support of NIH (SSS-3(5) ROl GM45260-2) is also greatly appreciated. 1 2 3 4 5 6 7 8 9 I 0 11 12 13 References Haugland, R. P., in Molcwdur Probes Hunclhook of Fluoromwt Probes und Rtwurch Clzemiculs, 5th edn., Molecular Probes Inc., Eugene, OR, 1992. Scudder, K. M., Christian. G. D., and RGiiEka, J . , Exp. Cell Kes., 1993, 205, 107. Berg, H. C., and Block, S. M . , 1. Gcw. Microbiol., 1984, 130, 291s. Scudder, K. M., Pollema, C. H., and RfiiiEka, J . , Anal. Chern., 1992, 64, 2657. KGiiEka, J . and Hanscn, E. H., in Flow Injeclion Arzulysis, Wiley-Interscience, New York. 2nd edn., 1988. Cozens-Roberts, C., Quinn, J . A., and 12auffcnburger, D. A., Biopliys. J., 1990, 58, 857. Moller, P. S . , Arvvnuuf. Q., 1963, 14, 163. Fowler. H. W., and McKay, A. J., in Microhiul Adhesion t o Surfuces, Ellis Horwood, Chichcster, 1980, pp. 143-161. Groves. B. J., and Riley, P. A., Cytohios, 1987, 52, 49. Cozens-Roberts, C., Quinn, J . A., and Lauffcnburger, D. A . , Riophys. J., I9Y0, 58, 107. Cozens-Roberts, C., Lauffenburger, D. A., and Quinn, J . A , , Biophys. J., 1990, 58, 841. Foley, M.. MacGregor, A. N., Kusel, J . R., Garland, P. B . , and Downie, T., J . Cell Biol., 1986, 103, 807. McKay, D . A.. Kuscl, J . K., and Wilkinson, P. C., J . CeIISci., 1991,100,473. Paper 3100800B Received February 9, I993 Accepted April 20, 1993

ISSN:0003-2654    

DOI:10.1039/AN9931801235

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYST, OCTOBER 1993, VOL. 118 1241 Measurement of the Sorption of Actinides on Minerals Using Microanalytical Techniques" John A. Berry, Hugh E. Bishop, Mark M. Cowper,+ Peter R. Fozard, John W. McMillan and Simon A. Mountfort AEA Technology, Harwell Laboratory, Didcot, Oxfordshire, UK OX1 I ORA The use of advanced surface-analytical techniques t o study the sorption of the actinides uranium and plutonium on to rocks and their consistuent minerals, in the context of radioactive waste disposal, is described. Nuclear microprobe analysis was used t o quantify the extent of sorption of actinides via Rutherford back-scattering (RBS); data on the minerals on which sorption had occurred were provided by particle- induced X-ray emission. Both surface and su b-surface concentrations of actinides were measurable.Secondary-ion mass spectrometry (SIMS) was used to measure qualitatively the distribution of sorbed actinides and their penetration rates into minerals. The equipment used at Harwell is described. Complementary use of both techniques in parallel is highly advantageous; RBS is used to quantify actinide surface loadings, with limited lateral and depth resolution, but, allied to SIMS, which has excellent spatial resolution, samples can be analysed both quantitatively and with high spatial resolution. Concentrations of uranium and plutonium sorbed on t o minerals can be routinely determined with sensitivities down to 1 ng cm-*. The data obtained are used to identify the minerals in a rock that are important for actinide sorption.Keywords: Actinide; sorption; mineral; nuclear microprobe analysis; secondary-ion mass spectrometry The movement of actinides, such as uranium and plutonium, from radioactive waste repositories through the geosphere is significantly retarded by sorption on to minerals in the rocks along fowpaths. The quantification of this sorption is central to an assessment of the safety of disposal of radioactive waste. While a large number of data have been presented in the literature regarding the extent of actinide sorption on to geological materials, much has been obtained by standard batch sorption (crushed rock) techniques, 1,2 which fail to identify t h e minerals of importance and their mechanistic role in actinide sorption. The objective of this study is to produce definitive information regarding the minerals in a rock that are important for actinide sorption from solution.The approach has been to expose intact rock samples, in the form of polished thin sections, t o solutions containing the actinides of interest. This has allowed the use of advanced surface analytical techniques: nuclear microprobe analysis and secondary-ion mass spectrometry (SIMS), in parallel, to determine qualitatively and quantitatively the distribution of uranium and plutonium sorbed on to a variety of rocks and their constituent minerals. Coupled with standard petro- graphic techniques, such as optical microscopy and electron- probe microanalysis (EPMA), the minerals that are important in the sorption of actinides for a given rock have been ide n t i fi ed .Nuclear microprobe analysis was selected for determining depth profiles and surface loadings of uranium and plutonium on individual minerals in rocks because the technique is particularly suitable for measuring heavy elements deposited on or near the surfaces of lighter substrates.3 The Harwell nuclear microprobe has been previously used to investigate the contamination of steels by thorium and plutonium."5 In those studies, Rutherford back-scattering (RBS) was used to measure surface-deposited actinides, while particle-induced X-ray emission (PIXE) and nuclear reactions were used to identify variations in substrate composition, particularly the presence of light element inclusions. The extension of the ' Presented at the Mccting Gcoanalytical Techniques: Current Capabilities.Future Potential, Milton Keynes. Buckinghamshire, UK, Octobcr 1, 19Y2. I To whom correspondence should be addressed. technique to the examination of actinides sorbed on rocks is described, with some background information on the method and the equipment. Rutherford back-scattering has been used to study the sorption of uranium and thorium on to calcite (CaCO3)." Secondary-ion mass spectrometry combines high elemental sensitivity, good spatial and depth resolution, and the ability to discriminate between isotopes. This combination has becn exploited to determine the distribution of trace elements and the isotopic abundance of elements in rock-forming minerals.' In this paper, the application of SIMS in the study of actinide sorption on to mineral surfaces is discussed.Experimental The sorption of uranium and plutoniutn on to four rock types has been studied: granite (an acid igneous rock), diorite (an intermediate igneous rock), dolerite (a basic igncous rock) and sandstone (a sedimentary rock). The coarse-grained nature of these rocks allowed mineralogical idcntificatiori of the phases on to which sorption occurred. The full experimental methodology used has been pub- lished previously,x but is summarized here. Polished thin sections of single minerals and rocks were prepared and characterized (in terms of mineralogy) by optical microscopy and X-ray diffraction. Mineral compositions were determined by EPMA.9 The sections were contacted with solutions containing trace amounts of uranium or plutonium for 1-6 months.Both synthetic groundwaters and ultra-high purity water were used as solutions. To reduce radiation levels, isotopes such as and Z4'Pu were used. These isotopes were sufficiently radioactive however, for the distribution of adsorbed radionuclides to be determined initially by a-auto- radiography. The tracks on the autoradiograph were corre- lated to minerals in each rock by optical microscopy; the autorudiographs were subsequently used as maps to pinpoint areas of high loadings. The surfaces of the sections werc thcn examined using the nuclear microprobe and SIMS. Methodology of Techniques Autoradiography After contact with the solutions, thc distributions of sorbed radionuclides on each polished section were initially deter- mined by autoradiographic techniques.The sections wereANALYST, OCTOBER 1993, VOL. 118 1241 Measurement of the Sorption of Actinides on Minerals Using Microanalytical Techniques" John A. Berry, Hugh E. Bishop, Mark M. Cowper,+ Peter R. Fozard, John W. McMillan and Simon A. Mountfort AEA Technology, Harwell Laboratory, Didcot, Oxfordshire, UK OX1 I ORA The use of advanced surface-analytical techniques t o study the sorption of the actinides uranium and plutonium on to rocks and their consistuent minerals, in the context of radioactive waste disposal, is described. Nuclear microprobe analysis was used t o quantify the extent of sorption of actinides via Rutherford back-scattering (RBS); data on the minerals on which sorption had occurred were provided by particle- induced X-ray emission.Both surface and su b-surface concentrations of actinides were measurable. Secondary-ion mass spectrometry (SIMS) was used to measure qualitatively the distribution of sorbed actinides and their penetration rates into minerals. The equipment used at Harwell is described. Complementary use of both techniques in parallel is highly advantageous; RBS is used to quantify actinide surface loadings, with limited lateral and depth resolution, but, allied to SIMS, which has excellent spatial resolution, samples can be analysed both quantitatively and with high spatial resolution. Concentrations of uranium and plutonium sorbed on t o minerals can be routinely determined with sensitivities down to 1 ng cm-*. The data obtained are used to identify the minerals in a rock that are important for actinide sorption.Keywords: Actinide; sorption; mineral; nuclear microprobe analysis; secondary-ion mass spectrometry The movement of actinides, such as uranium and plutonium, from radioactive waste repositories through the geosphere is significantly retarded by sorption on to minerals in the rocks along fowpaths. The quantification of this sorption is central to an assessment of the safety of disposal of radioactive waste. While a large number of data have been presented in the literature regarding the extent of actinide sorption on to geological materials, much has been obtained by standard batch sorption (crushed rock) techniques, 1,2 which fail to identify t h e minerals of importance and their mechanistic role in actinide sorption.The objective of this study is to produce definitive information regarding the minerals in a rock that are important for actinide sorption from solution. The approach has been to expose intact rock samples, in the form of polished thin sections, t o solutions containing the actinides of interest. This has allowed the use of advanced surface analytical techniques: nuclear microprobe analysis and secondary-ion mass spectrometry (SIMS), in parallel, to determine qualitatively and quantitatively the distribution of uranium and plutonium sorbed on to a variety of rocks and their constituent minerals. Coupled with standard petro- graphic techniques, such as optical microscopy and electron- probe microanalysis (EPMA), the minerals that are important in the sorption of actinides for a given rock have been ide n t i fi ed .Nuclear microprobe analysis was selected for determining depth profiles and surface loadings of uranium and plutonium on individual minerals in rocks because the technique is particularly suitable for measuring heavy elements deposited on or near the surfaces of lighter substrates.3 The Harwell nuclear microprobe has been previously used to investigate the contamination of steels by thorium and plutonium."5 In those studies, Rutherford back-scattering (RBS) was used to measure surface-deposited actinides, while particle-induced X-ray emission (PIXE) and nuclear reactions were used to identify variations in substrate composition, particularly the presence of light element inclusions. The extension of the ' Presented at the Mccting Gcoanalytical Techniques: Current Capabilities.Future Potential, Milton Keynes. Buckinghamshire, UK, Octobcr 1, 19Y2. I To whom correspondence should be addressed. technique to the examination of actinides sorbed on rocks is described, with some background information on the method and the equipment. Rutherford back-scattering has been used to study the sorption of uranium and thorium on to calcite (CaCO3)." Secondary-ion mass spectrometry combines high elemental sensitivity, good spatial and depth resolution, and the ability to discriminate between isotopes. This combination has becn exploited to determine the distribution of trace elements and the isotopic abundance of elements in rock-forming minerals.' In this paper, the application of SIMS in the study of actinide sorption on to mineral surfaces is discussed.Experimental The sorption of uranium and plutoniutn on to four rock types has been studied: granite (an acid igneous rock), diorite (an intermediate igneous rock), dolerite (a basic igncous rock) and sandstone (a sedimentary rock). The coarse-grained nature of these rocks allowed mineralogical idcntificatiori of the phases on to which sorption occurred. The full experimental methodology used has been pub- lished previously,x but is summarized here. Polished thin sections of single minerals and rocks were prepared and characterized (in terms of mineralogy) by optical microscopy and X-ray diffraction. Mineral compositions were determined by EPMA.9 The sections were contacted with solutions containing trace amounts of uranium or plutonium for 1-6 months.Both synthetic groundwaters and ultra-high purity water were used as solutions. To reduce radiation levels, isotopes such as and Z4'Pu were used. These isotopes were sufficiently radioactive however, for the distribution of adsorbed radionuclides to be determined initially by a-auto- radiography. The tracks on the autoradiograph were corre- lated to minerals in each rock by optical microscopy; the autorudiographs were subsequently used as maps to pinpoint areas of high loadings. The surfaces of the sections werc thcn examined using the nuclear microprobe and SIMS. Methodology of Techniques Autoradiography After contact with the solutions, thc distributions of sorbed radionuclides on each polished section were initially deter- mined by autoradiographic techniques.The sections wereANALYST, OCTOBER 1993, VOL. 118 1241 Measurement of the Sorption of Actinides on Minerals Using Microanalytical Techniques" John A. Berry, Hugh E. Bishop, Mark M. Cowper,+ Peter R. Fozard, John W. McMillan and Simon A. Mountfort AEA Technology, Harwell Laboratory, Didcot, Oxfordshire, UK OX1 I ORA The use of advanced surface-analytical techniques t o study the sorption of the actinides uranium and plutonium on to rocks and their consistuent minerals, in the context of radioactive waste disposal, is described. Nuclear microprobe analysis was used t o quantify the extent of sorption of actinides via Rutherford back-scattering (RBS); data on the minerals on which sorption had occurred were provided by particle- induced X-ray emission.Both surface and su b-surface concentrations of actinides were measurable. Secondary-ion mass spectrometry (SIMS) was used to measure qualitatively the distribution of sorbed actinides and their penetration rates into minerals. The equipment used at Harwell is described. Complementary use of both techniques in parallel is highly advantageous; RBS is used to quantify actinide surface loadings, with limited lateral and depth resolution, but, allied to SIMS, which has excellent spatial resolution, samples can be analysed both quantitatively and with high spatial resolution. Concentrations of uranium and plutonium sorbed on t o minerals can be routinely determined with sensitivities down to 1 ng cm-*. The data obtained are used to identify the minerals in a rock that are important for actinide sorption.Keywords: Actinide; sorption; mineral; nuclear microprobe analysis; secondary-ion mass spectrometry The movement of actinides, such as uranium and plutonium, from radioactive waste repositories through the geosphere is significantly retarded by sorption on to minerals in the rocks along fowpaths. The quantification of this sorption is central to an assessment of the safety of disposal of radioactive waste. While a large number of data have been presented in the literature regarding the extent of actinide sorption on to geological materials, much has been obtained by standard batch sorption (crushed rock) techniques, 1,2 which fail to identify t h e minerals of importance and their mechanistic role in actinide sorption.The objective of this study is to produce definitive information regarding the minerals in a rock that are important for actinide sorption from solution. The approach has been to expose intact rock samples, in the form of polished thin sections, t o solutions containing the actinides of interest. This has allowed the use of advanced surface analytical techniques: nuclear microprobe analysis and secondary-ion mass spectrometry (SIMS), in parallel, to determine qualitatively and quantitatively the distribution of uranium and plutonium sorbed on to a variety of rocks and their constituent minerals. Coupled with standard petro- graphic techniques, such as optical microscopy and electron- probe microanalysis (EPMA), the minerals that are important in the sorption of actinides for a given rock have been ide n t i fi ed .Nuclear microprobe analysis was selected for determining depth profiles and surface loadings of uranium and plutonium on individual minerals in rocks because the technique is particularly suitable for measuring heavy elements deposited on or near the surfaces of lighter substrates.3 The Harwell nuclear microprobe has been previously used to investigate the contamination of steels by thorium and plutonium."5 In those studies, Rutherford back-scattering (RBS) was used to measure surface-deposited actinides, while particle-induced X-ray emission (PIXE) and nuclear reactions were used to identify variations in substrate composition, particularly the presence of light element inclusions.The extension of the ' Presented at the Mccting Gcoanalytical Techniques: Current Capabilities. Future Potential, Milton Keynes. Buckinghamshire, UK, Octobcr 1, 19Y2. I To whom correspondence should be addressed. technique to the examination of actinides sorbed on rocks is described, with some background information on the method and the equipment. Rutherford back-scattering has been used to study the sorption of uranium and thorium on to calcite (CaCO3)." Secondary-ion mass spectrometry combines high elemental sensitivity, good spatial and depth resolution, and the ability to discriminate between isotopes. This combination has becn exploited to determine the distribution of trace elements and the isotopic abundance of elements in rock-forming minerals.' In this paper, the application of SIMS in the study of actinide sorption on to mineral surfaces is discussed.Experimental The sorption of uranium and plutoniutn on to four rock types has been studied: granite (an acid igneous rock), diorite (an intermediate igneous rock), dolerite (a basic igncous rock) and sandstone (a sedimentary rock). The coarse-grained nature of these rocks allowed mineralogical idcntificatiori of the phases on to which sorption occurred. The full experimental methodology used has been pub- lished previously,x but is summarized here. Polished thin sections of single minerals and rocks were prepared and characterized (in terms of mineralogy) by optical microscopy and X-ray diffraction. Mineral compositions were determined by EPMA.9 The sections were contacted with solutions containing trace amounts of uranium or plutonium for 1-6 months.Both synthetic groundwaters and ultra-high purity water were used as solutions. To reduce radiation levels, isotopes such as and Z4'Pu were used. These isotopes were sufficiently radioactive however, for the distribution of adsorbed radionuclides to be determined initially by a-auto- radiography. The tracks on the autoradiograph were corre- lated to minerals in each rock by optical microscopy; the autorudiographs were subsequently used as maps to pinpoint areas of high loadings. The surfaces of the sections werc thcn examined using the nuclear microprobe and SIMS. Methodology of Techniques Autoradiography After contact with the solutions, thc distributions of sorbed radionuclides on each polished section were initially deter- mined by autoradiographic techniques.The sections were1244 ANALYST, OCTOBER 1993, VOI,. 118 less sensitive than the IMS 3F, it requires a much lower extraction field to collect the secondary ions. This reduces the problems of charge neutralization. Mass spectra, ion images and depth profiles have all been obtained from uncoated samples. Charge neutralization is achieved using a beam from an auxiliary electron gun. However, although the instrument is capable of high magnifi- cations, the magnification for these mineral samples is still limited by charging. The highest magnification that can be achieved is very sample dependent, but is typically limited to a minimum field of view in the range 100-500 pm.A second problem is that different phases in the mineral section can charge differentially and it is only possible to obtain optimum neutralization for one phase at a time. In spite of these limitations, it proved possible to map the distribution of phases in a rock through a set of ion images and to image the distribution of sorbed uranium on the surface. It was also possible to obtain depth profiles from particular phases. Results and Discussion Nuclear Microprobe The type of PIXE spectrum produced by the irradiation of minerals with 2 MeV 4He+ is shown in Fig. 3 for an ilmenite (FeTi03) crystal in dolerite exposed to uranium(v1) solutions. The low bremsstrahlung contribution to X-ray spectra gener- ated by ion irradiation is evident.This lowers backgrounds and enhances detection limits. The characteristic iron and titanium X-rays expected for this mineral are the most abundant in the spectrum, with evidence for the presence of minor amounts of manganese, calcium and aluminium. L and M series lines from the uranium occur at similar energies, but are not observed in Fig. 3 because of their low yields compared with the K lines of the rock-forming elements. The positions of two silicon escape peaks3 from the titanium K a and KB X-ray peaks are also shown. The ilmenite crystal was chosen for nuclear microprobe examination because a-autoradiography indicated that uran- ium had sorbed strongly on to this mineral. The RBS spectrum obtained simultaneously with the PIXE spectrum is shown in Fig. 4. The principal features are a high energy surface peak, the actinide region, and a series of superimposed plateaux associated with the substrate mineral composition.The high- energy edge of the first plateau is not inconsistent with the presence of hafnium, and the second zirconium, which are probably associated with the titanium. The next two plateau edges are attributable to iron and titanium. Finally, small edges are indicated for calcium and oxygen, which have decreasingly small RBS cross-sections. Simulation of the RBS 5 4 h 2 3 3 u v 3 2 1 0 Ti Fe X-ray energy -+ Fig. 3 PIXE spectrum of an ilmenite crystal in diorite after immersion in a uranium solution. Ti* arc silicon escape peaks due to the interaction between titanium K a and Kfi X-rays and the Si(Li) detector spectrum was used to deduce the sub-surface penetration of the uranium.The simulated and measured RBS spectra are in good accord (Fig. 4). The depth profile for uranium derived from the simulation is shown in Fig. 5 and indicates that the concentration falls rapidly to 1 ng cm-z at little more than 0.1 pm from the surface. The integrated total loading derived from the uranium depth profile is 107 ng cm-2, compared to a surface loading obtained by simple comparison with the 230Th standard of 90 ng cm-2. This shows that most of the sorbed uranium(v1) is on the surface of the ilmenite crystal. In a study on the sorption of uranium(v1) from granitic water on to granite, using uranium 93% enriched in 2 3 W , good agreement was obtained between surface loadings measured by a-autoradiography , fission- track analysis and RBS.The measured range of surface loadings for the major minerals in the granite are presented in Table 1. The RBS spectra not only reveal the surface loading and penetration of actinides on mineral substrates, but can also reveal modification of the substrate itself. The RBS spectrum of a dolomite grain in sandstone exposed to a uranium solution is shown in Fig. 6. The broad surface peak indicates that uranium has penetrated a considerable distance into the substrate. The peaked iron plateau shows that iron is also concentrated near the specimen surface, co-depositing with the uranium. As the dolomite contains iron, the change in its surface concentration has probably been caused by substrate dissolution accompanied by iron re-deposition.Other aspects of these results have been discussed previously .s The correlation of actinide surface absorption with the composition of substrate minerals can be revealed by line scanning. The results obtained for the sorption of uranium on 4 1 3 - c [I) c 3 v 8 2 0, J 1 1 ... Actinide region \d .. . . . . 0 ' Fig. 4 data; ~ computer simulated spectrum I Recoil energy- RBS spectrum of the ilmenite crystal. * * . * . * Experimental 60 120 180 240 300 DeptMnrn Fig. 5 on the RBS spectrum (Fig. 4) Derived uranium depth profile for the ilmenite crystal based Table 1 Surface loadings of uranium on granitic minerals (ng cm-?) Plagio- Measurement Alkali clase MUSCO- technique Quartz feldspar feldspar Biotite vite a-Autoradiography 5-11 3-17 1C26 2CL100 2CL80 Fission track analysis 10-30 11-21 2040 40-90 - N ucl e ar micro pro be RBS analysis 5-15 12-18 10-30 50-210 30-110ANALYST, OCTOBER 1993, VOL.118 1245 minerals in a diorite specimen are shown in Fig. 7 The variations in the distributions of calcium, titanium, aluminium and potassium, as measured by PIXE, show that the line scan crosses four mineral grains, namely, a plagioclase feldspar [Na(Ca)AISi,O,], a potassium feldspar (KAISi3O8>, sphene (CaTiSiOS) and a second grain of potassium feldspar. The RBS results for uranium show that it is preferentially sorbed on to sphene. Experiments with plutonium are underway. Preliminary results have shown that plutonium, like uranium, is preferen- tially sorbed on specific phases, such as biotite and ilmenite, in granite, dolerite and sandstone sections.Loadings of up to 30 and 50 ng cm-2 have been observed for biotite and ilmenite, respectively. Secondary-ion Mass Spectrometry In an earlier paper,” the penetration of uranium into minerals was investigated by immersing thin sections of granite in 1 or 20 ppm uranium solutions for 2-3 months. Depth profiles were 41 1 I I Recoil energy -+ Fig. 6 RBS spectrum of a dolomite crystal in a sandstone sample after immersion in a uranium solution. Spectral features associated with the prcscncc of U (actinide region), Fe, Ca, Mg and 0 are indicated Calcium 0 0.5 1 .o 1.5 Distance/mm Fig. 7 Nuclear microprobe scan across diorite sample obtained with use of both X-ray photoelectron spectroscopy (XPS) and SIMS (with the IMS 3F).The uranium concentra- tions were close to the detection limits of XPS, but the results afforded an absolute surface concentration of uranium. As SIMS is a much more sensitive technique, the uranium depth profiles were recorded with a diagnostic range of over two orders of magnitude. Fig. 8 shows an IMS 3F depth profile for uranium sorbed on to a quartz grain. The first part of the profile has been fitted to a first-order diffusion equation with a rate of 1 x 10-22 m2 s-I , but the tail of the profile is significantly higher than the fitted curve, suggesting a second transport mechanism was opera- tive. Furthermore, the calculated diffusion rate is much greater than that obtained by extrapolating solid-state diffu- sion data from high-temperature studies to room temperature.This increase was interpreted as a small number of fast transport paths, such as microfissures, resulting in aqueous phase uranium diffusion. Ion images obtained with an MAS00 gallium microprobe showed clearly the presence of uranium in surface defects such as cracks and polishing pits in minerals. When the surface was sputtered, uranium remained at depth within defects in the lattice. However, it was not possible to say whether the uranium was genuinely sorbed on to mineral surfaces or trapped in residual solution drawn by capillary action into cracks, microfissures and grain boundaries. In order to resolve this problem, thin sections of granite were immersed in solutions containing 0.5 mol dm-3 potas- sium iodide and 3.4 x mol dm-3 uranium.After coating the specimens with gold, depth profiles were recorded in the TMS 3F and the samples were then transferred to the MAS00 gallium microprobe where ion images were recorded from the TMS 3F sputter pits. Fig. 9(a) shows a sodium ion image from such a pit in a perthite [(Na,K)AlSi,O,J grain. The rectangular area shows where the gold coating has been sputtered away. The darker patch in the centre of this area is due to incomplete charge neutralization. Fig. 9(h) shows the 235UO+ image superimposed on the sodium ion image. There is a strong correlation between uranium and cracks and other defects observed in the sodium image at the base of the sputter pit [Fig. 9(b)]. This confirms that the deeper penetration of uranium into the minerals is due to transport through cracks and provides an explanation for the higher diffusion coeffi- cients observed in earlier studies.17 Ion images of the same area for iodide were blank, showing that iodide had been removed by washing.If the uranium was simply present in solution trapped in the microfissures, iodide should also be present. Likewise, if the ‘trapped’ solution had evaporated in the microfissures (precipitating dissolved salts) both uranium and iodide should have been preserved. Therefore, the SIMS study shows that: (a) simple washing of the sample removes non-sorbing iodide from microfissures while uranium remains sorbed at depth, possibly o n to secondary phases; (b) the diffusion coefficients observed in earlier studies,l7 where D, 4000 c = 1000 t ;c\ 0 0.1 0.2 0.3 0.4 Distance/pm Fig.8 Diffusion profile of quartz from SIMS data. Data points; - -theoretical curve for D = 2.0 X 10-2z m7 s-l; - - - - theoretical curve for D = 1.0 x lop2’ m2 s-’ANALYST, OCTOBER 1993, VOL. 118 1245 minerals in a diorite specimen are shown in Fig. 7 The variations in the distributions of calcium, titanium, aluminium and potassium, as measured by PIXE, show that the line scan crosses four mineral grains, namely, a plagioclase feldspar [Na(Ca)AISi,O,], a potassium feldspar (KAISi3O8>, sphene (CaTiSiOS) and a second grain of potassium feldspar. The RBS results for uranium show that it is preferentially sorbed on to sphene. Experiments with plutonium are underway. Preliminary results have shown that plutonium, like uranium, is preferen- tially sorbed on specific phases, such as biotite and ilmenite, in granite, dolerite and sandstone sections.Loadings of up to 30 and 50 ng cm-2 have been observed for biotite and ilmenite, respectively. Secondary-ion Mass Spectrometry In an earlier paper,” the penetration of uranium into minerals was investigated by immersing thin sections of granite in 1 or 20 ppm uranium solutions for 2-3 months. Depth profiles were 41 1 I I Recoil energy -+ Fig. 6 RBS spectrum of a dolomite crystal in a sandstone sample after immersion in a uranium solution. Spectral features associated with the prcscncc of U (actinide region), Fe, Ca, Mg and 0 are indicated Calcium 0 0.5 1 .o 1.5 Distance/mm Fig. 7 Nuclear microprobe scan across diorite sample obtained with use of both X-ray photoelectron spectroscopy (XPS) and SIMS (with the IMS 3F).The uranium concentra- tions were close to the detection limits of XPS, but the results afforded an absolute surface concentration of uranium. As SIMS is a much more sensitive technique, the uranium depth profiles were recorded with a diagnostic range of over two orders of magnitude. Fig. 8 shows an IMS 3F depth profile for uranium sorbed on to a quartz grain. The first part of the profile has been fitted to a first-order diffusion equation with a rate of 1 x 10-22 m2 s-I , but the tail of the profile is significantly higher than the fitted curve, suggesting a second transport mechanism was opera- tive. Furthermore, the calculated diffusion rate is much greater than that obtained by extrapolating solid-state diffu- sion data from high-temperature studies to room temperature.This increase was interpreted as a small number of fast transport paths, such as microfissures, resulting in aqueous phase uranium diffusion. Ion images obtained with an MAS00 gallium microprobe showed clearly the presence of uranium in surface defects such as cracks and polishing pits in minerals. When the surface was sputtered, uranium remained at depth within defects in the lattice. However, it was not possible to say whether the uranium was genuinely sorbed on to mineral surfaces or trapped in residual solution drawn by capillary action into cracks, microfissures and grain boundaries. In order to resolve this problem, thin sections of granite were immersed in solutions containing 0.5 mol dm-3 potas- sium iodide and 3.4 x mol dm-3 uranium. After coating the specimens with gold, depth profiles were recorded in the TMS 3F and the samples were then transferred to the MAS00 gallium microprobe where ion images were recorded from the TMS 3F sputter pits. Fig. 9(a) shows a sodium ion image from such a pit in a perthite [(Na,K)AlSi,O,J grain. The rectangular area shows where the gold coating has been sputtered away. The darker patch in the centre of this area is due to incomplete charge neutralization. Fig. 9(h) shows the 235UO+ image superimposed on the sodium ion image. There is a strong correlation between uranium and cracks and other defects observed in the sodium image at the base of the sputter pit [Fig. 9(b)]. This confirms that the deeper penetration of uranium into the minerals is due to transport through cracks and provides an explanation for the higher diffusion coeffi- cients observed in earlier studies.17 Ion images of the same area for iodide were blank, showing that iodide had been removed by washing. If the uranium was simply present in solution trapped in the microfissures, iodide should also be present. Likewise, if the ‘trapped’ solution had evaporated in the microfissures (precipitating dissolved salts) both uranium and iodide should have been preserved. Therefore, the SIMS study shows that: (a) simple washing of the sample removes non-sorbing iodide from microfissures while uranium remains sorbed at depth, possibly o n to secondary phases; (b) the diffusion coefficients observed in earlier studies,l7 where D, 4000 c = 1000 t ;c\ 0 0.1 0.2 0.3 0.4 Distance/pm Fig. 8 Diffusion profile of quartz from SIMS data. Data points; - -theoretical curve for D = 2.0 X 10-2z m7 s-l; - - - - theoretical curve for D = 1.0 x lop2’ m2 s-’

ISSN:0003-2654    

DOI:10.1039/AN9931801241

出版商:RSC    

年代:1993

数据来源: RSC