摘要:

ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 Analytical Division Diary DECEMBER Wednesday, lst, 6.30 p.m.: Birmingham Midlands Region: Annual General Meeting. Is Separation Needed to Analyse Complex Matrices or Can It All be Done by Numbers? Debate lead by M. Adams and R. M. Smith. Chemistry Department, The University, Birmingham. There are no registration formalities. Contact: Dr. R. M. Smith, Department of Chemistry, University of Technology, Loughborough, Leicestershire LEI 1 3TU. (Tel. 0509-222563; Fax 0509-233 163). Thursday, 2nd, 4.30 p.m.: Cardiff Western Region, jointly with thc South East Wales Section of the RSC. Monitoring Air Pollutants Beyond the Works Boundary. Speaker: P. S . Jarrett. Small Chemistry Lecture Theatre, University of Wales College of Cardiff.There are no registration formalities. Contact: Dr. S. J. Hill, Department of Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA. (Tel. 0752-233012; Fax 0752-232293). Thursday, 9th, 10 a.m.: London Joint Pharmaceutical Analysis Group. The Role of Pharmacopoeias. ‘The New BP and RP (Veterinary)’, by D. Gandcrton. Views from the Pharmaceutical Industry. Speakers: J . C. Wahlich. I. R. Humphrey and A. J . Woolfc. ‘The View of the Independent Analyst’. by A. Davidson. ‘A Hospital View’, by R. F. Haines-Nutt. ‘A UK Licensing Authority View’, by A. C. Cartwright. 111 ‘Harmonization of Rcquiremcnts’. by A. R. Rogers. ... The Royal Pharmaceutical Society of GB, 1 Lambeth High Street, London SE1 7JN.Registration is necessary. Cost f45 to members, f70 to non- members and &25 to student, unemployed and retired members. Contact: Dr. J. Clements, The Royal Pharmaceutical Society of GB, 1 Lambeth High Street, London SE1 7JN. (Tel. 07 1-735-914 I ). Wednesday, 15th, 9.30 a.m.: London South East Region and Automutic Methods Group (Annual General Meetings), in conjunction with the Health and Safety Executive. Workplace and Environment Monitoring - The Boundary Layer. ‘Impact of Legislation’, by J . Firth. ‘Monitoring Stratcgics for Workplace and Environmental Assess- mcnt’, by P. Lcinster. ‘Quality Assurance and Accrcditation’, by K. Varvill. ‘Devclopmcnt and Validation of Measurement Methods’, by R. Brown. ‘Dusts and Acrosols’, by L. Kenncy. ‘Thc Usc o f Diffusive Monitors‘, by K. Saundcrs. ‘Continuous Monitoring’, by P. Clarke. ‘Aldchydcs and Indoor Air’, by D. Crump and M.-A. Gavin. ‘Monitoring Acid Gas Emissions’, by A. Braithwaite and C . Hills. ‘Purge and Trap Tcchniqucs’, by R. Largc. ‘Analytical Techniques for VOCs in Soil and Land’, by P. Simpson. ‘Conclusions and Futurc Devclopmcnts’, by J. Firth. Scientific Societies Lecture Theatre, New Burlington Place, London Wl . Registration is necessary. Cost to RSC members f75, non- members 595, and students and retired members &45. Contact: Dr. R. Narayanaswamy, DIAS, UMIST, P.O. Box 88, Manchester M60 1QD. (Tel. 061-200-4891/4885; Fax 061-200-491 1).

ISSN:0144-557X    

DOI:10.1039/AP993300P004

出版商:RSC    

年代:1993

数据来源: RSC

ISSN:0144-557X    

DOI:10.1039/AP99330FX041

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

November 1993 ANPRDI 30( 1 1 ) 41 7-468 (1 993) Analytical Proceedings Proceedings of the Analytical Division of The Royal Society of Chemistry CONTENTS 41 7 Editorial 41 7 Euroanalysis Vlll 41 8 Sampling Club 419 New Members of Council 422 VAM Viewpoint 'Establishment of an Infrastructure for the Measurement of Aerosols and Particulates in the Gas Phase' 429 429 43 1 433 438 440 441 442 445 424 Analytical Viewpoint 'Ion Chromatographic Analysis of Acetate and-Formate Ions Produced by Sonolysis of Aqueous Saturated Solutions of Sodium Hydrogencarbonate' by F. Castellani, G. Vitali, G. Berchiesi and R. Giovannetti 428 426 SUMMARIES OF PAPERS 426 Trace Analysis 426 427 'Stopped-flow Method for Low Levels of Hydroxylamine in Water' by M.M. Abubaker, L. S. Bark, A. K. Davies and F. Z. Shtewi 'Kinetic Method for the Determination of Trace Amounts of Copper(l1) Ion in Boiler Water' by M. M. Abubaker, L. S. Bark, A. K. Davies and F. Z. Shtewi 'Trapping of Radioiodine on Charcoal: Performance and Particle Size' by Colin G. Taylor, Giles Kay, Duangjai Nacapricha and Michael F. Pimlett 'Use of Thin-Layer Chromatography with Flame-ionization Detection t o Assess Oil Upgrading During the in situ Combustion Process for Enhanced Oil Recovery' by D. Price, A. Millington and R. Hughes 'Poisonous Exudates of Millipedes' by C. P. Fairhurst 'Cavity Walls in Solution: New Reagents for Luminescence Trace Analyses in Aqueous Media?' by John R. Ebdon, David M. Lucas, Ian Soutar and Linda Swanson 'Pinks and Blues' by A.Atkinson 'On-line Immobilized Chelating Agents in Flow Injection Systems' by G. M. Greenway and A. Townshend 'Applications of Trace Metals Analysis at ICI Specialties Research Centre' by Sharon C. Stephen 'Analysis of Pentachlorophenol Using Extraction Methods, Derivatization and Gas Chromatography-Mass Spectrometry' by E. Helen Jenkins and Peter J. Baugh 'Preconcentration Methods for Determination of Copper, Cadmium, Lead and Zinc in Surface Waters: A Comparative Study' by Frederick Vernon and Cosmas D. Wani 'Trace Elements in Natural Zeolites' by Alan Dyer, lsaaq Zaafarany and Gordon R. Gilmore 'Particle Sizing (On-line) in Crystallization' by M. W. Wedd 'Characterizing Crystal Habit and Perfection: A Calibration Strategy' by C.J. Price 'Crystallization Kinetics: The Role of Particle Characterization' by C. J. Price 'Phase-characterizing Polymorphs and Solvates' by Peter York 'Characterizing Crystal Habit and Habit Modification' by Stephen J. Maginn 'Crystal Size and Size Distribution: The Role of Test Sieving' by John W. Mullin 'Particle Breakage, Abnormal Growth and Agglomeration During Industrial 447 The Role of Particle Characterization in Industrial Crystallization 447 449 451 452 453 455 456 458 Crystallization' by Alan G. Jones 'Sucrose Crystal Nucleation and Growth' by Dennis J. Brown, Keith R. Cliffe and Ian M. Grimsey 460 Equipment News 464 Analytical Chemistry Trust Fund 465 Conferences and Meetings 467 Courses 111 ... Analytical Division Diary 0144-557XC1993111:1-F ... 111 ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 COPIES OF CITED ARTICLES The Royal Society of Chemistry Library can usually supply copies of cited articles. For further details contact: The Library, Royal Society of Chemistry, Burlington House, Piccadilly, London WIV OBN, UK. Tel: +44 (0)71-437 8656 Fax: +44 (0)71-287 9798 Tclccom Gold 84: BUR210 Electronic Mailbox (Internet) LIBRARY@RSC.ORG. If the material is not available from the Society’s Library, thc staff will be pleased t o advise on its availability from othcr sources. Please note that copies are not available from the RSC at Thomas Graham Housc. Cambridge.

ISSN:0144-557X    

DOI:10.1039/AP99330BX043

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 417 Euroanalysis Vlll The Euroanalysis VIII conference was held in Edinburgh from Sunday, Sep- tember 5 , to Saturday, September 11, 1993. The opening event was a mixer reception, held in the Halls of Residence. This was attended by the majority of people who were already in residence and featured some of the beer donated to the conference by a local brewery. One of the major events of any inter- national conference is the opening cere- mony. This is particularly true of Euro- analysis conferences, which tend to include a number of award presentations as well as the opening speeches. Thus, following the welcomes by Professor D. Thorburn Burns (Chairman of the Praesi- dium), Professor J. Mavor (Dean of the Faculty of Science and Engineering, Edinburgh University), Professor L.Niinisto (FECYWPAC) and Professor A. Hulanicki (IUPAC), awards were made to Professor A. Amirav of Tel Aviv University, Israel (The Heinrich Emanuel Merck Award), Professor D. Thorburn Burns of the Queen's University, Belfast, Northern Ireland (The Fritz Pregl Medal Professor L. Niinisto speaking at the opening ceremony instruments Dr. R. Andrews and Dr. M . Harriott viewing part of the Playfair Collection of Scientific41 8 ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 The scene of the conference banquet in the Royal Scottish Museum of the Austrian Society for Analytical Chemistry), Professor L. Niinisto of Hel- sinki University of Technology, Finland (Honorary Membership of the Austrian Society for Analytical Chemistry) and Professor T.Fujinaga of Kyoto Univer- sity, Japan (the Robert Boyle Gold Medal of the Analytical Division of the Royal Society of Chemistry). Professor Fujinaga was not able to be present in person. These formalities were followed by an informative Historical Lecturedelivered by Professor Thorburn Burns on the subject of ‘Dark Ages to Enlightenment, Alchemy to Analysis: Progress in Scottish Chemistry within a European Framework’. The conference was now, of course, open in earnest and excellent scientific and social programmes unfolded as the week progressed. The lectures were as well attended as could be expected with about 680 scientific conferees distributed between five parallel streams and the attractions of the city of Edinburgh vir- tually on the doorstep. The poster ses- sions, carefully arranged in the McEwan Hall, were very well attended and discus- sions continued until nearly 6 p.m.on all three afternoons on which they were organized. The enthusiasm of all 750 conferees was illustrated by the unprece- dented number of people who packed into Lecture Theatre D of the Appleton Tower for the Closing Ceremony at 4 p.m. on the Friday afternoon. There were approximately 6 spare seats in the 200- seater theatre. The Social Programme was also varied and well-organized. Among the highlights were the Tuesday evening events, a whisky tasting (organized by Mr. R. 1. Aylott of United Distillers plc and featur- ing a talk by Mr. T. Cowan of Invergor- don Distillers Ltd.) and a recital given by the Organist of the University of Edin- burgh, Dr.John Kitchen. Dr. Kitchen performed a programme of early music on one of the harpsichords which is kept in St. Cecilia’s Hall, and also accompanied a bass, Mr. Nigel Brookes, who sang various songs from the same period. The Professor A . Hulanicki at the Opening Ceremony tours on the Wednesday were also well received and were an excellent oppor- tunity to talk to other conferees at greater length than is usually possible in a crowded programme. The most spectacu- lar event was probably the Thursday night buffet dinner, held in the Royal Scottish Museum, at which the Playfair collection of Scientific Instruments and the Fox- Talbot photographic collection were on view. Overall, my impression of the confer- ence is of a blur of activity, with the pace never flagging from Sunday night’s dinner to Saturday’s breakfast. It was totally exhausting but very enjoyable and reflected great credit on the local organizers from the Scottish Region of the Analytical Division of the Royal Society of Chemistry, and also on the heroic stewards from various Scottish and other British Universities who worked extremely hard to make the event a success. R. A. YOUNG

ISSN:0144-557X    

DOI:10.1039/AP993300417b

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

41 8 ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 Sampling Club The club is being set up jointly by Cranfield Institute of Technology and the Laboratory of the Government Chemist as part of the DTI’s Valid Analytical Measurement (VAM) initiative. Intrinsically difficult to sample mater- ials range from coarse heterogeneous solids, through pastes, cohesive powders and emulsions, to multi-phase liquid or gas-based streams. They can also include high or low temperature materials and those requiring isolation from the general environment. Sampling can be for labora- tory, ‘on the spot’, on-line analysis or other quality determination. Locations can vary from pipelines through reactors and hoppers to delivery vehicles, as well as hazardous and sensitive environments or locations. Such materials and sampling problems are found widely in the process industries, foodstuffs, chemicals, pharmaceuticals, mineral processing, cement and metal production all being typical.There is no point in having first rate analysts, expen- sive instruments or state of the art sensors if the sample is not representative or has altered prior to analysis. Objectives of the Club The primary objective of the club is to assist its industrial members with Sam- pling intrinsically difficult materials, The club will seek to highlight and discuss issues relating to heterogeneous, unstable and other intrinsically difficult to sample materials, locations and other sampling problems.ANALYTICAL PROCEE:DINGS, NOVEMBER 1993, VOL 30 419 It is proposed to locate and utilize existing expertise, share experience and foster collaborative solutions to the many problems that exist in not only reliably taking a representative sample but indeeed taking a sample at all! While recognizing the uniqueness of many over- all problems, it will seek generic solutions to commonly found problem components in sampling systems designed to meet such requirements.The club maintains a regularly updated database of consultants, systems and equipment supplies for the benefit of members. Regular technical meetings are held with presentations, discussion and reports on generic solutions to problem areas. Members define the topics for ‘state of the art’ reports and interaction between members is encouraged to define and support research into problem areas. In addition, a consultancy service will be provided to members at highly advan- tageous rates, initial discussions and one day’s consultancy being free to each member organization for every full year of membership. Membership Fees will be as follows: Trade Association, Industrial Company El000 + VAT Consortium 21500 + VAT Small-Medium Employers (less than 500 employees) 2500 + VAT Academic Departments &200 + VAT For further information or appli- cation forms contact Ken Carr-Brion, Department of Fluid Engineering and Instrumentation, Cranfield Institute of Technology, Bedford MK43 OAL (Tel: 0234-754739; Fax: 0234-750728) or Derek Woods, LGC, Queens Road, Tedd- ington, Middlesex TWll OLY (Tel: 081-943-7432; Fax: 081-943-2767).

ISSN:0144-557X    

DOI:10.1039/AP9933000418

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYTICAL PROCEE:DINGS, NOVEMBER 1993, VOL 30 419 New Members of Council Gerry Best is a recently elected Member of Council. The last time he was on Council was ten years ago when he was Chairman of the Scottish Region and he provided a biographical summary which appeared in Analytical Proceedings in August, 1983. He has been co-opted to serve on the Scottish Region committee again. He is still employed at the Clyde River Purification Board as its Principal Fresh- water Scientist and is not far off getting his watch for 25 years’ service. Although the Board’s task remains the same, to improve and maintain the quality of waters in the West of Scotland, it con- stantly provides new challenges because of new pollution problems and analytical demands. A decade ago, the idea of using GC-MS in his laboratories was just a dream but now the Board has two bench- top machines which are used to analyse for a variety of insecticides, herbicides and other organic substances in environ- mental samples.Similarly with ICP-MS, which is likely to be purchased in the near future to extend the range and automa- tion of trace metals analysis. The latest challenge is to achieve NAMAS accredi- tation for the laboratories by 1995. His interest in environmental education has continued and he was recently co- author of a book ‘Environment and Eco- logy’ which is used by ‘A’-level biology pupils, He has contributed chapters to other books on gas chromatography, the effects of afforestation on water quality and the chemistry of Loch Lomond. His latest book is as a result of collaboration with Professor Jan Dojlido of Warsaw and is entitled ‘The Chemistry of Water and Water Pollution’.Gerry Best is a visiting lecturer to Strathclyde University but also gives many talks to interested lay groups. Environmental issues are popular topics for Rotary Clubs, Men’s Associations and Women’s Groups! Outside his work, his life has under- gone some marked changes in recent years. He recently remarried after the death of his first wife and now has doubled the number of his children: all four, fortunately, are grown up, but his two daughters have each produced a grand- child who provide a lot of fun. He continues to have a masochistic interest in running but now it is only the occasional half marathon rather than the full 26+ miles of 10 years ago.His fictional writing remains unpublished as yet, but one day 3 . . .. Peter Brawn was born in Sandy, Bedford- shire, and was educated at Sandy Primary School and Stratton School, Biggleswade. His interest in chemistry began at about the time of this change of school and was initiated by a chemistry set as a Christmas present. By the end of the next term he had exhausted the range of experiments supplied with the set and had moved on to the study of pyrotechnics! Suprisingly, after leaving school in 1964, he did not rush off to join ICI’s Nobel Division, but instead joined the Unilever Research Laboratory at Col- worth House, Sharnbrook, as a Technical Assistant in the Organic Chemistry Section. His initial work was on the synthesis of germicides and he recalls many hours spent preparing novel com- pounds, some of which turned out to be quite successful (one compound earned Unilever in excess of $1 million in patent royalties).At the same time ,,e began to think seriously how he could make amends for some rather disappointing A-level results and started the long haul to qualifications via the part-time day release study route. This eventually led to GradRIC, MRSC CChem and then FRSC. In 1970, he was accepted for a PhD in Molecular Spec- troscopy with Dr. McKillop at the Univer- sity of East Anglia, but declined to take this up because his interests were begin- ning to broaden into biochemistry, and there was the possibility of an offer of an420 ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 internal PhD.This offer unfortunately did not materialize, although he did obtain an MSc in Biochemistry (with distinction) from the University of London. He spent several years working in the fields of enzyme technology and enzymo- logy before joining the Analytical Section at Colworth in 1976, where he initially worked with Geoff Telling on trace conta- minants analysis. After 10 years in analy- tical toxicology he was eventually made responsible for all analytical support to Unilever’s Environmental Safety Labora- tory at Colworth, and was appointed Section Manager of the Chemistry Section. Two years later, in 1992, he was appointed Section Manager of the Analy- tical Section, a section of 63 people providing analytical support to the Col- worth site and to Unilever’s operating companies, and this is more or less his current job.He has been active in the RSC since the 1970s, first as a committee member of the Special Techniques Group, and then as Secretary, and currently Chairman, of the East Anglia Region of the Analytical Division. He is also a member of the Chemical Aspects of Toxicology (CHAO- TIC!) Discussion Group. He is married to Mary and has a son and a daughter. His spare time interests are photography, DIY, snooker and walking. His son is already showing some pyro- technic tendencies so perhaps there is another chemist in the making, but in these days of safety consciousness we would not want him to start his career with a bang! John R. Dean was born in Preston and was educated at Fulwood and Cadley Primary School, and then Fulwood High School. ‘A’ levels were taken at W.R. Tuson College before attending the University of Manchester Institute of Science of Technology (UMIST). In 1981 he was awarded a BSc degree in chemistry, followed a year later by a BSc Honours degree. This having stimulated an interest in analytical chemistry, he successfully completed the MSc course in Analytical Chemistry and Instrumentation at Lough- borough University. His project, super- vised by Dr. Tony Edmonds, was on the use of carbon fibre electrodes for voltam- metric analysis. This subsequently led to a publication (T. E. Edmonds and S. Latif) some years later (1988). Upon completion of his masters degree he embarked on a PhD in analytical chemistry, sponsored by the Laboratory of the Government Chemist, at Imperial College of Science and Technology.This project, supervised by Dr. R. D. Snook, studied the mecha- nism of sample introduction in atomic spectroscopy, principally electrothermal vaporization and laser ablation studies for inductively coupled plasmas. Upon com- pletion of his thesis in December 1985 he became a research fellow at the Food Science Laboratory of the Ministry of Agriculture, Fisheries and Food in Nor- wich, employed by the University of Plymouth (formerly Plymouth Polytech- nic), where he was responsible for the development of analytical methods appropriate to inductively coupled plasma mass spectrometry (ICP-MS). This project, a continuation of work started by Dr. S. Munro, was guided by Dr. Rob Massey (MAFF) and Professor Les Ebdon (Plymouth), with collabor- ation from Dr.Helen Crews, on the development of chromatographic tech- niques for trace element speciation in foodstuffs using ICP-MS. These elements were principally cadmium in pig kidney and arsenic in chicken meat. The collab- oration has realised 11 publications to date (with 2 more in the pipeline!). In December, 1987, Dr. Dean took up a Temporary Lectureship at the Hudders- field Polytechnic (now University of Hud- dersfield) in Inorganic Chemistry, followed a year later by a lectureship in Inorganic/Analytical chemistry at New- castle Polytechnic (now University of Northumbria at Newcastle). As well as a full timetable of lectures and laboratory classes Dr. Dean has striven to maintain his research interests.However, a lack of funding rapidly persuaded him to re- evaluate his research interests. These ‘new’ activities arrived in 1990 in the form of glow discharge sources and supercriti- cal fluid extraction! The former was funded by a Society of Analytical Chemistry Industrial Studentship in col- laboration with Dr. John Marshall at ICI plc, Wilton Research Centre, and the latter by a jointly funded venture between ICI plc, Wilton Reseach Centre (Drs. Bill Campbell and Chris Dowle), and Glaxo Manufacturing Services (Mr. Ken Leiper and Dr. Roy Tranter). While both have benefited from another new-found inter- est in chemometrics, it is the application of supercritical fluid extraction which has shown the most potential for successful industrial implementation. In fact, the work on supercritical fluids has subse- quently attracted further funding/ collaboration from Phase Separations Ltd., Analytical and Environmental Services Ltd.(Northumbria Water plc), Pfizer Central Research and Zeneca plc. Dr. Dean has recently edited a book entitled ‘Applications of Supercritical Fluids in Industrial Analysis’. At present Dr. Dean has published over 40 publica- tions in analytical chemistry. Dr. Dean had been active within the RSC-AD since 1985, and has served on the Atomic Spectroscopy Group and North East Region committees with cur- rent responsibilities as the Honary Secre- tary and Honorary Assistant Secretary, respectively. He is also a member of the Atomic Spectrometry Updates Editorial Board and SAC ’95 organizing com- mittee. His recent (August 1992) inclu- sion on the Register of Analytical Chemists appears to make him fairly unique! He is married to wife Lynne and they have two children, Sam and Naomi.He relaxes with an occasional game of squash and gardening. Nothing of any consequence has hap- pened to Stan Greenfield since his last biography which appeared in the December, 1989, issue (p. 418) except, possibly, the award of a DSc by Lough- borough University of Technology, where he is still a visiting Professor. His interests are, as many would expect, still in the use of ICP, although he has been known to be diverted on occasion into other related topics, such as microwave digestion. He is currently investigating, with the assistance of col- leagues and students, how the ICP in existing commercial instruments may be used as a source and as an atodion cell in other spectroscopies by suitable retro- fitting .His other interests are, as ever, travel- ling (particularly in Italy where he has a home), wine, food and cooking. He has changed his MGB for a convertible and his staid old fishing boat for a speedboat in420 ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 internal PhD. This offer unfortunately did not materialize, although he did obtain an MSc in Biochemistry (with distinction) from the University of London. He spent several years working in the fields of enzyme technology and enzymo- logy before joining the Analytical Section at Colworth in 1976, where he initially worked with Geoff Telling on trace conta- minants analysis. After 10 years in analy- tical toxicology he was eventually made responsible for all analytical support to Unilever’s Environmental Safety Labora- tory at Colworth, and was appointed Section Manager of the Chemistry Section.Two years later, in 1992, he was appointed Section Manager of the Analy- tical Section, a section of 63 people providing analytical support to the Col- worth site and to Unilever’s operating companies, and this is more or less his current job. He has been active in the RSC since the 1970s, first as a committee member of the Special Techniques Group, and then as Secretary, and currently Chairman, of the East Anglia Region of the Analytical Division. He is also a member of the Chemical Aspects of Toxicology (CHAO- TIC!) Discussion Group. He is married to Mary and has a son and a daughter.His spare time interests are photography, DIY, snooker and walking. His son is already showing some pyro- technic tendencies so perhaps there is another chemist in the making, but in these days of safety consciousness we would not want him to start his career with a bang! John R. Dean was born in Preston and was educated at Fulwood and Cadley Primary School, and then Fulwood High School. ‘A’ levels were taken at W. R. Tuson College before attending the University of Manchester Institute of Science of Technology (UMIST). In 1981 he was awarded a BSc degree in chemistry, followed a year later by a BSc Honours degree. This having stimulated an interest in analytical chemistry, he successfully completed the MSc course in Analytical Chemistry and Instrumentation at Lough- borough University.His project, super- vised by Dr. Tony Edmonds, was on the use of carbon fibre electrodes for voltam- metric analysis. This subsequently led to a publication (T. E. Edmonds and S. Latif) some years later (1988). Upon completion of his masters degree he embarked on a PhD in analytical chemistry, sponsored by the Laboratory of the Government Chemist, at Imperial College of Science and Technology. This project, supervised by Dr. R. D. Snook, studied the mecha- nism of sample introduction in atomic spectroscopy, principally electrothermal vaporization and laser ablation studies for inductively coupled plasmas. Upon com- pletion of his thesis in December 1985 he became a research fellow at the Food Science Laboratory of the Ministry of Agriculture, Fisheries and Food in Nor- wich, employed by the University of Plymouth (formerly Plymouth Polytech- nic), where he was responsible for the development of analytical methods appropriate to inductively coupled plasma mass spectrometry (ICP-MS).This project, a continuation of work started by Dr. S. Munro, was guided by Dr. Rob Massey (MAFF) and Professor Les Ebdon (Plymouth), with collabor- ation from Dr. Helen Crews, on the development of chromatographic tech- niques for trace element speciation in foodstuffs using ICP-MS. These elements were principally cadmium in pig kidney and arsenic in chicken meat. The collab- oration has realised 11 publications to date (with 2 more in the pipeline!). In December, 1987, Dr. Dean took up a Temporary Lectureship at the Hudders- field Polytechnic (now University of Hud- dersfield) in Inorganic Chemistry, followed a year later by a lectureship in Inorganic/Analytical chemistry at New- castle Polytechnic (now University of Northumbria at Newcastle). As well as a full timetable of lectures and laboratory classes Dr.Dean has striven to maintain his research interests. However, a lack of funding rapidly persuaded him to re- evaluate his research interests. These ‘new’ activities arrived in 1990 in the form of glow discharge sources and supercriti- cal fluid extraction! The former was funded by a Society of Analytical Chemistry Industrial Studentship in col- laboration with Dr. John Marshall at ICI plc, Wilton Research Centre, and the latter by a jointly funded venture between ICI plc, Wilton Reseach Centre (Drs.Bill Campbell and Chris Dowle), and Glaxo Manufacturing Services (Mr. Ken Leiper and Dr. Roy Tranter). While both have benefited from another new-found inter- est in chemometrics, it is the application of supercritical fluid extraction which has shown the most potential for successful industrial implementation. In fact, the work on supercritical fluids has subse- quently attracted further funding/ collaboration from Phase Separations Ltd., Analytical and Environmental Services Ltd. (Northumbria Water plc), Pfizer Central Research and Zeneca plc. Dr. Dean has recently edited a book entitled ‘Applications of Supercritical Fluids in Industrial Analysis’. At present Dr. Dean has published over 40 publica- tions in analytical chemistry.Dr. Dean had been active within the RSC-AD since 1985, and has served on the Atomic Spectroscopy Group and North East Region committees with cur- rent responsibilities as the Honary Secre- tary and Honorary Assistant Secretary, respectively. He is also a member of the Atomic Spectrometry Updates Editorial Board and SAC ’95 organizing com- mittee. His recent (August 1992) inclu- sion on the Register of Analytical Chemists appears to make him fairly unique! He is married to wife Lynne and they have two children, Sam and Naomi. He relaxes with an occasional game of squash and gardening. Nothing of any consequence has hap- pened to Stan Greenfield since his last biography which appeared in the December, 1989, issue (p. 418) except, possibly, the award of a DSc by Lough- borough University of Technology, where he is still a visiting Professor.His interests are, as many would expect, still in the use of ICP, although he has been known to be diverted on occasion into other related topics, such as microwave digestion. He is currently investigating, with the assistance of col- leagues and students, how the ICP in existing commercial instruments may be used as a source and as an atodion cell in other spectroscopies by suitable retro- fitting . His other interests are, as ever, travel- ling (particularly in Italy where he has a home), wine, food and cooking. He has changed his MGB for a convertible and his staid old fishing boat for a speedboat in422 ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 Society, initially as a committee member of the Mid-Anglia Section, and has the distinction of being Chairman of the Section when amalgamation took place in 1980. In more recent years he has served on the East Anglia Regional committee of the Analytical Division, and was Chair- man of the Section between 1984 and 1986. He has served for several years on the Analytical Division Council, both as a co-opted member and as an elected member. In 1993 he was elected Vice- President of the Division. He is married to Diana, an analytical chemist with a major pharmaceutical company, and has two teenage children. He does not have time for many outside interests; however, he does like to play tennis and golf on the odd occasion, both of which he admits to doing very badly. He is, however, quite good at drinking real ale, enjoys travelling abroad, particu- larly France, and is a lifelong Arsenal supporter.

ISSN:0144-557X    

DOI:10.1039/AP9933000419

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

422 ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 Establishment of an Infrastructure for the Measurement of Aerosols and Particulates in the Gas Phase Aerosols are playing an ever increasing role in science, engineering, industrial hygiene and environmental protection. Such product and safety related appli- cations have reinforced the need for a metrological system which relates measurements to primary standards by traceable procedures. An important part of this process is the development of suitable methods for sampling, analysis and calibrating equipment. Part of the Valid Analytical Measurement (VAM) Initiative is to establish an infrastructure of aerosol-based measurements. The project is being co-ordinated by a con- sortium consisting of AEA Technology, Warren Spring Laboratory and the Natio- nal Physical Laboratory.The main task during the next 18 months is to develop a national calibration facility for aerosol analysis (NCFAA) which will co-ordinate the development of valid calibation and measurement techniques. In addition to defining the role of the NCFAA, several sub-tasks have been identified as important. To produce a series of ‘cocktail’ reference materials, containing mix- tures in known proportions of monodisperse polystyrene latex (PSL) microspheres. To examine the scope to develop CRMs based on particle shape. To examine the scope for developing reference techniques to provide aero- sol number- and mass-concentration sources (aerosol concentration standards). To ascertain the requirements for biological, aerosol-based standards.To develop and disseminate guide- lines on sampling procedures. A questionnaire was sent in 1992 to individuals able to represent the views of industrial organizations. At that stage, the primary aims were to identify needs and priorities, and to determine if a body is required to co-ordinate the develop- ment of aerosol standards applying to each part of the measurement process. The survey established strong support for all aspects of the programme, and many individuals expressed a desire to see the initiative operating beyond the UK. As a result, all parts of the programme are to be implemented, although at the present time their exact scope remains to be fully defined. ‘Cocktail’ Particulate Certified Reference Materials (CRMs) ‘Cocktail’ CRMs are well defined mix- tures containing two or more monodis- perse components at known relative pro- portions.Polystyrene latex microspheres (PSL) are the most readily available and well-characterized source of particles to form the basis of these CRMs; they are required by users of particle analysers who need either simultaneous calibration with several sizes of particle, or an indica- tion of the resolving capability of the technique. This might also be used to diagnose problems associated with instru- ment sensitivity and sampling difficulties. Four ‘cocktails’ are to be produced during the next 18 months, with the proposed formulations: cocktail A: cocktail B: cocktail C: cocktail D: component sizes 0.1, 0.2 and 0.5 pm volume equivalent diameter; component sizes 0.2, 0.5 and 1.0 pm volume equivalent diameter; component sizes 0.5, 1.0 and 3.0 pm volume equivalent diameter; component sizes 1.0, 3.0 and 10.0 ym volume equivalent diameter. A small number of independent labora- tories will be invited to certify the relative proportions of each component within a ‘cocktail’ maintained as a liquid suspen- sion using traceable techniques ( e .g . , electrical sensing zone analysis). Prescrip- tive methods will be developed to gener- ate these CRMs as aerosols, and guidance will be provided on their use with com- monly available aerosol analysis equipment. Particle Shape Standards Recent developments in the field of sili- con micromachining have made it poss- ible to produce uniform sized particles that have well defined three-dimensional shapes. Such particles can truly be termed ‘shape standards’, because their micros- copy measured (geometric) and fluid resistance (dynamic) shape factors can be controlled precisely within a limited over- all size range.It is foreseen that such standards will be useful in assessing shape-related effects in particle analysis equipment, particularly in the field of health-related aerosol measurement. It is foreseen that at least one set of CRMs could be produced based on fibre ana- logues, with a fixed l pm depth and width and variable lengths from 1 to 10 pm. Guidance will also be provided on their generation as calibration aerosols. Aerosol Concentration Standards The feasibility study has confirmed the need for aerosol concentration standards based on uniform sized particles. The emphasis will initially be placed on the characterization of portable calibration sources (based on PSL aerosols), rather than the development of single ‘reference’ facilities, such as the electrical mobility classifier and vibrating-orifice system.ANALYTICAL PROCEEDINGS, NOVEMBER 1993.VOL 30 423 However, some work on the latter will be necessary to support the operation of the portable systems. Major applications for such standards are the calibration of total particle detectors (condensation nucleus counters and optical particle counters) that are widely used in the microelectro- nics industry, as well as the calibration of respirable mass concentration dust monitors used in air quality assessments of the workplace.BiologicaVMicrobiological Reference Materials The appropriateness and practicality of validating and certifying selected bioaero- sols for use as airborne reference mater- ials have been evaluated. Bioaerosols as a group form a complicated and highly specialized area of measurement, and the survey has confirmed the usefulness of standard calibrants as well as an urgent need for better defined sampling and collection methodologies. For instance, sampling devices must be capable of collecting a representative sample of species such as micro-organisms without compromising their biological activity. Better standards are required in this area because bioaerosols are important to human health, and contaminant levels need to be reduced in specific industrial processes.Bioaerosols are also increas- ingly utilized in the process industries, as well as the more traditional activities such as public health and hygiene. It is fore- seen that the development of calibrant aerosols based on bacteria, bacterial spores and fungal spores will be possible. Development of Sampling Guidelines A comprehensive review has shown that there is a wide variety of recommended methods available for sampling aerosols. However, this information is scattered throughout the literature and, as a result, it is difficult to obtain guidance quickly for a specific application. In addition, there is little consistency in the scope and quality of the information offered, and little guidance on their effective application. A set of up-to-date sampling guidelines will therefore be collected and produced to address the major requirements, with emphasis being placed on advice to the user in applying the most relevant guide- line to the situation in hand.Each guide- line will be available in document and computer readable form. Consultations have taken place with a representative sample of industrial-based contacts to seek their advice on priorities. A limited number of areas have been identified as being in need of new guide- lines, and are as follows: dust in the ambient atmosphere; oil mists and air- borne droplets; biological aerosols; direct reading instruments for (a) process control, (b) stack emissions; design of entries and sampling lines of particle size analysers; personal monitoring of welding fumes; sampling of large radioactive par- ticles from the atmosphere; and dust emissions from machines and material handling processes.It is anticipated that a simple-to-use expert system will be devel- oped to guide the user in the selection of the most appropriate sampling technique for a variety of situations. The Establishment of the National Calib- ration Facility for Aerosol Analysis (NCFAA) The formation of nationally recognized body to co-ordinate the calibration activi- ties for a wide variety of aerosol anlaysis equipment would reduce the costs to industry which result from the present ad hoc arrangements. It is intended that the NCFAA would operate in the following way. Day-to-day operation of the NCFAA will be controlled through its Secretariat, which will provide enquirers with information about the activities of the organization, together with publicity material relating to suppliers of calib- ration services, certified reference mater- ials and guidelines for the valid calibration and use of aerosol analysis equipment.The Technical Advisory Committee (TAC) will function as the main Working Group, acting as a forum where represen- tatives from the service companies, ‘experts’ from the particle science community and regulatory bodies can meet. Guidelines for equipment calib- ration and use will be produced through the operation of the TAC and made available to users. The NCFAA will encourage the accreditation of such sup- pliers to recognized bodies in the field, such as the NAMAS Executive; support from the National Physical Laboratory will enable the development of the necess- ary infrastructure for introducing accredi- tation in the field of aerosol analysis.The NCFAA will also assist manufacturers and service suppliers to meet any calib- ration related requirements that may be introduced by new legislation. An import- ant activity foreseen for the TAC may be the development and operation of type approvals services for certain critical applications. The NCFAA will also provide specia- lized evaluation services for specific instruments, particularly new techniques or applications. Such services, however, will of necessity be negotiated on a one- off basis. Links will be fostered with external bodies capable of influencing the develop- ment of such a calibration infrastructure on a regional or world-wide basis, e.g., the European Bureau of Community Reference (BCR) and the US National Institute of Standards and Technology (NIST). For further information contact: Dr. Jolyon P. Mitchell, Aerosol Science Centre, AEA Technology, A50/010 Win- frith Technology Centre, Dorchester, Dorset DT2 8DH (Tel: 0305-203293; Fax: For further details about the VAM Initiative, please contact Greta Car- penter, LGC (Tel: 081-943-7393). 0305-202351).

ISSN:0144-557X    

DOI:10.1039/AP9933000422

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

424 ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 Analytical Viewpoint The following is a member of a continuing series of articles providing either a personal view of part of one discipline in analytical chemistry (its present state, where it may be leading, etc.), or a philosophical look at a topic of relevance to chemists in general or analytical chemists in particular. These contributions need not have been the subject of papers at Analytical Division Meetings. Persons wishing to provide an article for publication in this series are invited to contact the editor of Analytical Proceedings, who will be pleased to receive manuscripts or t o discuss outline ideas with prospective authors. Ion Chromatographic Analysis of Acetate and Formate Ions Produced by Sonolysis of Aqueous Saturated Solutions of Sodium Hydrogencarbonate F.Castellani, G. Vitali and G. Berchiesi Dipartimento di Scienze Chimiche, Via S. Agostino 1, Universita degli Studi di Camerino, 62032 Camerino, Italy R. Giovannetti Centro lnterdipartimentale Grandi Apparecchiature, P. le G. da Varano, Universita degli Studi di Cam erino, 62032 Came rin 0, ltal y The use of ultrasound to enhance chemical reactions is becoming increasingly interesting in chemistry. 1-9 Therefore, in order to examine the possible effects of cavitation produced ultrasonically in saturated electrolyte solutions, the system NaHC03 + H20 was sonicated. Experiments were performed using an ultrasonic cleaner bath and an ion chromatograph. The measurements showed that the cavitation phenomenon resulted in the formation of OH-, HC02- and CH3COO- ions in solution, and of C02 gas.The existence of these species may be explained by a reaction mechanism involving H. and *OH radicals. lo,l' Experimental Sonol ysis An ultrasonic cleaner from Heat Systems (Model 7E) was employed, operating at 20 kHz and dissipating 0.775 W cm-2. A saturated aqueous sodium hydrogencarbonate solution (Carlo Erba, RPE-ACS Grade), contained in a 50 ml flask, was tightly fixed just above the bottom of the sonicator. The samples (7 g NaHC03 + 30 ml de-ionized water) were sonicated for various lengths of time ranging from 1 week to 1 month. In addition, a saturated aqueous solution of sodium carbonate (18 g) (Carlo Erba, RPE-ACS) and de-ionized water (30 ml) was sonicated for 1 month. Product Analysis A significant volume of C 0 2 was produced.Subsequently a qualitative analysis of the liquid fraction (pH = 10) was carried out. The presence of oxalate ions was excluded, although some organic ions were formed because KMn04 (0.02 mol 1-') was decolorized in the presence of carbonate ions.12 Their forma- tion and identification were demonstrated using a Dionex 4500i ion chromatograph (Fig. 1). The eluent employed was Na2B407*10H20 (4.9 mmol 1-*). Results and Discussion After obtaining the calibration graphs of the acetate and formate ions, quantitative analysis of the samples was per- formed by ion chromatography (IC). The values obtained are reported in Table 1 while the plots of the mass of ions produced versussonication time show an exponential trend (Figs.2 and 3). 0 3 6 Time/min Fig. 1 Anion chromatogram of saturated sodium hydrogencarbonate solution sonicated for 4 weeks. A , OH-; B, CH3COO-; C, HCOO-; D, HCO,-; and E , C03*-. Operating conditions were as follows: sample volume, 50 pl; guard column, Ion Pac AG4A; analytical column, Ion Pac AS4A; eluent flow rate, 2 ml min-'; anion micro- membrane suppressor, AMMS-1; regenerant. 12.5 mmol 1-' H2S04; regenerant flow rate, 3-5 ml min- '; expected background conduc- tivity, 2-4 pS Table 1 Amount of acetate and formate ions after sonication Sample* B4L B3L B2L B1L C4L c 4 s B3S Sonication time/weeks 4 3 2 1 4 4 3 A~etate/lO-~ g 12.59 6.31 4.36 3.92 30.85 143.37 5.83 Formate/10-3 g 0.25 0.09 0.07 0.07 0.39 4.47 2.64 * B = sodium hydrogencarbonate; C = sodium carbonate; L = liquid fraction; S = solid fraction.ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 0.25 0.20 0) ? 3 0.15 z E \ LL 0.10 425 - - - - 0 2 4 Time/weeks Fig.2 Amount of formate ions produced in the liquid fraction versus sonication time 0 2 4 Time/weeks Fig. 3 sonication time Amount of acetate ions produced in the liquid fraction versus In order to explain the reaction mechanism, a sample of hydrogencarbonate to which was added 0.4 g of sodium acetate was analysed and sonicated for 3 weeks. An increase in intensity of the formate peak of the chromatogram was observed, relative to that of the sample sonicated for the same time but without acetate ions. The equilibrium of acetate formation was probably shifted towards the formate ions due to the effect of the common ion.The total mass of formate ion in samples B3L + H3S was greater than that in sample B4L which lacks the solid fraction (see Table 1). These two observations prove that the mechanism of formation of acetate ions involves the formation of the formate ion as a first step. The proposed mechanism is: + H2O (2) / H /OH \0- \0- + 2-H S O=C o=c + H202 CH3COO- + CO5- + 0 2 + H20 /Yo 3H-C, '0- (3) For the sonication of carbonate, a difference in the first step of the reaction mechanism is proposed since in this reaction C02 was not formed. + OH- (4) /H /O- \0- \0- + 2.H O=C o=c Over the time range examined, optimum efficiency was achieved after sonication for 4 weeks. The total amount of acetate obtained from samples C4L + C4S was about 10-fold higher than that obtained from sample B4L, which lacks the solid fraction.This phenomenon is probably due both to the higher initial concentration of carbonate (2.5-fold higher than the hydrogencarbonate concentration) and to the absence of C02 production, thus preventing the carbonate ion from being lost. 1 2 3 4 5 6 7 8 9 10 11 12 References Mason, T. J . , and Lorimer, J . P.. Sonochemistry, Theory, Applications and Uses of Ultrasounds in Chemistry, Ellis Horwood, Chichester, 1988. Han, B. H., and Boudjouk, P., Tetrahedron Lett., 1982, 23, 1643. Petrier, C., and Luche, J . L., Tetrahedron Lett., 1987,28,2347. Fuentes, A., Marinas. J . M., and Sinisterra, J. V., Tetrahedron Lett., 1987, 28, 4541. Petrier, C., De Suoza Barbosa, J . C.. Dupuy, C., and Luche, J. L., J . Org. Chem., 1985, 50, 5761. Elpimer, I. E., Sokolskaya, A. V., and Margulis, M. A., Nature (London). 1965, 208, 945. Farhat, F., and Berchiesi. G., Synfh. Commun., 1992,22,3137. Farhat. F., and Berchiesi, G.. Proceedings of the 3rd Meeting of the European Society of Sonochemistry. Figueira da Foz, Portugal, 1993. p. 61. Castellani, F., Vitali, G., and Giovannetti, R., Proceedings of the 3rd Meeting of the European Society of Sonochemistry, Figueira da Foz, Portugal, 1993, p. 123. Mason, T. S . , Chemistry with Ultrasound. SCI Elsevier Applied Science, London and New York. 1990, p. 100. Suslick. K. S . . Ultrasound Its Chemical, Physical and Biological Effects, VCH, New York, 1988, p. 138. Vogel, A. I., A Textbook of Quantitative Inorganic Analysis, Longman, London. 1961, 3rd edn., p. 301.

ISSN:0144-557X    

DOI:10.1039/AP9933000424

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

426 ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 Trace Analysis A symposium to honour the retirement of Professor L. S. Bark was organized by the North West and Northern Ireland Regions of the Analytical and Industrial Divisions. The following are summaries of twelve of the papers presented at the meeting, which was held on October 9, 1992, in the University of Salford. Stopped-flow Method for Low Levels of Hydroxylamine in Water M. M. Abubaker, L. S. Bark, A. K. Davies and F. 2. Shtewi Department of Chemistry and Applied ChemistryI University of Salford, Salford M5 4 WT The broad aims of the study are to develop sensitive and selective kinetic methods for the assay of water used for the production of steam in high temperature, high pressure boilers. The water used in this application is of potable quality.Hydroxylamine and/or hydrazine are added to the water as corrosion inhibitors; it is important, therefore, to be able to determine trace amounts of these compounds remaining in the treated water so that the concentrations of these inhibitors added to the water can be optimized. For the purposes of the present investigation attention was focused on hydroxylamine. In a paper dealing with the determination of bromide ion in water by the chloramine T-phenol red method, Jones' showed that there was strong interference by hydroxylamine. This led the present authors to the idea that a chloramine T-dye system might form the basis of a sensitive indicator reaction for the determination of trace amounts of hydroxylamine by a kinetic method. It was expected that hydroxylamine would compete with the dyestuff for chloramine T and hence the rate of bleaching of the dyestuff would be decreased, enabling a calibration graph of rate versus hydroxylamine concentration to be constructed. Experimental A stopped-flow apparatus was used, because it was expected that the reactions would be fairly rapid.The principle of the stopped-flow technique is quite straightforward. Reactant solutions are driven simultaneously from two syringes into a mixing chamber, from where the mixed solution passes into an optical cell and then to waste. When the drive block attached to the syringes hits a stop, the flow of mixed reactant solutions comes to an abrupt halt. The progress of the reaction is then followed by measuring the change in absorbance of a beam of monochromatic light, which is directed through the cell onto a sensitive photodiode.The signal from this detector is recorded as a trace on an oscilloscope screen, mV recorder or computer monitor. From the trace, the initial rate of reaction, the rate constant or some other parameter of the reaction can be measured. The applications of the stopped-flow technique in analytical chemistry have been reviewed.2 The technique offers the advantages of convenient sample handling and fast sample throughput. Repeat runs on the same sample are particularly easy to accomplish. Accurate measurement of low absorbance changes is possible because the cell is permanently fixed in position relative to the light beam. Experiments were carried out to determine the optimum pH, the type of buffer required, the reactant concentrations, etc., and, based on these experiments, the following procedure was used.The two drive syringes were filled with solutions (A) and (B). Solvtion (A) was composed of citric acid - sodium citrate buffer solution (pH 3.0,0.05 mol dm-3), dye solution (2 x mol dm-3) and hydroxylamine (one of a number of standards ranging in concentration from 2 x lop6 to 2 x mol dmP3, or a water sample of unknown concentration). Solution (B) was chloramine T solution (0.001 mol dm-3). Solutions (A) and (B) were mixed in the stopped-flow apparatus and the change in absorbance was monitored at a wavelength which depended on the particular dye. Several oxidizable dyes were investigated; each one gave rise to a different, and quite distinctive, kinetic trace.Indigo carmine was selected for further study because it gave an initial sharp peak, the height of which depended on the hydroxyl- amine concentration. With this dye the absorbance change was measured at 593 nm. Results and Discussion Contrary to the expected reduction in the rate of dye bleaching with increasing hydroxylamine concentration, the presence of hydroxylamine greatly increased the rate of bleaching. The reaction trace showed a rapid increase in absorbance as fresh reaction mixture flushed the previously bleached solution from the stopped-flow cell. This was followed (when the flow stopped) by a rapid partial bleaching of the indigo carmine, then by a very slow bleaching process. The height ( h ) of the initial bleaching step was measured from the recorder chart.A calibration graph of h versus the hydroxylamine Concentration was linear, although extrapolation to zero hydroxylamine concentration gave a small intercept on the peak-height axis. Measurement of the peak height ( h ) for a water sample, and reference to the calibration graph, enabled the hydroxylamine concentration to be determined down to 0.1 ppm, with a relative precision of +2%. The mechanism of reaction involved in this sensitive and selective method is the subject of further investigation. However, some insight into the mechanistic features is provided by the fact that the rate of the initial bleaching step is independent of hydroxylamine concentration (i. e. , zero order). This shows that hydroxylamine is involved in a fast step which is not rate-determining.It was suspected that the rate- determining step was the formation of hypochlorous acid (HOCI) from chloramine T. This was confirmed by pre-mixing the citrate buffer (pH 3.0) with chloramine T before mixing it with the indigo carmine-hydroxylamine solution in the stopped-flow cell. The results of this experiment showed that when HOCl had been allowed to accumulate in this way, the initial bleaching step was much faster. This supports the proposal that HOCl formation is the slow step. When the time of contact between chloramine T and pH 3.0 buffer was increased beyond about 1 min, the rate of the initialANALYTICAL PROCEEDINGS. NOVEMBER 1993. VOL 30 427 bleaching step did not show any further increase.This result indicates that the equilibrium involving HOCl formation is established in less than 1 min under the conditions of the experiment. Based on these observations the following outline scheme is proposed (here RNClNa represents chloramine T, IC represents indigo carmine and X represents an interme- diate, as yet unidentified). RNClNa +- RNCl- + Na+ + RNCl- -t H+ RNHCl 2RNHCI + RNClz + RNHZ ---+ Slow --+ RNHCl + HOCl Slow -----) t- Decolorized IC RNCIz -t HzO HOCl + IC Fast HOCl + NH20H- X Fast x + I C ---+ Decolorized IC Intermediate X is evidently a more powerful bleaching agent than HOCl for indigo carmine. An exhaustive study of potentially interfering substances has not yet been completed but the effect of a few likely ones has been studied.Thus, when an aqueous solution of hydroxyl- amine is allowed to stand, several products (arising from aerial oxidation and other reactions such as disproportionation) are likely to be present: for example, nitrite and ammonium ions. In industrial boiler water, hydrazine may be present together with ions such as chloride. Of these, hydrazine and ammonium ion in the range 2 X 10-6-1.2 X mol dmW3 do not interfere. Chloride ion does not interfere but bromide ion and nitrite ion do. The latter interfering anions can be removed by a short (4 cm) anion-exchange column in its chloride form, without affecting the concentration of hydroxylamine. The original aim of the investigation was to develop a kinetic method of analysis for hydroxylamine. The method described is not a kinetic one because it relies on measurement of the magnitude of an initial fast bleaching step rather than the rate of bleaching.This proved to be advantageous as it made the method robust with respect to temperature; variation between the limits 19-28 "C can be tolerated because, although the rate of bleaching changes, the height ( h ) is affected only very slightly. References 1 2 Jones, D. R . , Tafanfa, 1989, 36, 1243. Hiromi, K., and Kanaya, K., Anal. Sci., 1988, 4, 445. Kinetic Method for the Determination of Trace Amounts of Copper(ii) Ion in Boiler Water M. M. Abubaker, L. S. Bark, A. K. Davies and F. 2. Shtewi Department of Chemistry and Applied Chemistry, University of Salford, Salford M5 4 WT A knowledge of the levels of impurities in water to be used for the production of steam in high temperature, high pressure boilers is important if corrosion is to be minimized.One impurity of interest in this respect is the Cu" ion, which may be present mainly as a consequence of transportation of water through copper pipes and brass valves. A low cost method for measuring Cu" ion in boiler water was required which would be sensitive, selective and rapid, and which would require simple apparatus capable of being automated. Some of the most sensitive methods of analysis are kinetic methods involving catalysed reactions and the one described here for Cu" is of this type. The Cu"-catalysed oxidation of ascorbic acid has been known for many years' and is a suitable reaction for kinetic analysis in many respects.It suffers from the drawback that one of the reactants is a dissolved gas (oxygen), the concentration of which may not be known with certainty. Thermometric2 and spectrophotometric' methods have been used to measure the rate of reaction but they'd0 not provide information on the concentration of oxygen. The solution to this problem was to use an oxygen sensor which measures, at one and the same time, both the oxygen concentration and the rate of reaction. Experimental The polarographic oxygen sensor used in this work is an electrochemical cell with a platinum cathode and a silver anode. The electrolyte is saturated potassium chloride solu- tion. A voltage of 0.6 V is applied across the two electrodes so that, when oxygen is present, the platinum electrode becomes depolarized and a current flows by virtue of the following electrode reactions. At the cathode (Pt): O2 + 2H+ + 2e- -+ H202 H202 + 2H+ + 2e- -+ 2H20 Ag + CI- --.) AgCl + e- and At the anode (Ag): The current, which is of the order of a few microamperes, is amplified and displayed (as an equivalent voltage) on a millivolt recorder.The current is directly proportional to the concentration of oxygen in the solution contained in the reaction vessel. In practice this solution is separated from the electrodes and electrolyte by a 25 pm thick PTFE membrane, through which oxygen diffuses freely. The principal design feature of the oxygen sensor that makes it suitable for kinetic analysis is the reaction vessel, which has a removable plunger with a central capillary.This allows the addition of solutions to be made to the reaction medium while the reaction trace is being recorded. The effect of such an addition is therefore instantly registered as a change in the slope of the trace, which means that very small effects can be detected. The determination of Cu" ion was carried out as follows. Ascorbic acid solution (2.0 cm3, 6.6 x mol dm-3) and acetate buffer solution (1.0 cm3, 0.20 mol dm-', pH 4.6) were pipetted into the reaction vessel. The plunger was replaced and air bubbles were displaced through the central capillary tube. The stirrer was started and a stead trace was obtained on the recorder chart. An addition of Cur solution (one of a series of standards, or a water sample) was made by means of a syringe while recording of the trace was continued.The copper(i1)- catalysed rate of oxygen absorption was calculated from the difference in slope of the trace measured before and after sample addition. r428 ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 Results and Discussion Two series of standard aqueous solutions of copper(1r) sulfate were prepared covering the ranges from 1.6 X rnol dm-3 to 1.6 X mol dmV3. For both ranges, graphs of the Cu"-catalysed rate of oxygen absorption versus the Cu" ion concentration were linear and passed through the origin. From these calibration graphs the concentration of Cu" ion in water samples could be determined with a relative precision of approximately &2%. The validity of the oxygen sensor method was confirmed by comparison of the results for various water samples with results obtained by using atomic absorption spectroscopy.The two sets of results were in good agreement, as is shown in Table 1. A thorough investigation of possible interferences has not yet been completed but chloride ion does not interfere, neither does fluoride (up to 3 x rnol dm-3). A number of transition metal ions, namely Ni", Mn", Co", Fe" and Fe"' (up to 1.6 x loh5 mol dmP3) have no significant effect. Magnesium(r1) ion does not interfere. The use of the polarographic oxygen sensor for the determination of CU" ion by the catalysed oxidation of ascorbic acid provides a simple, reliable and selective method which has the added advantage of being inexpensive. The equipment is portable and the method could be adapted for use rnol dm-3 and 1.6 x to 1.33 x Table 1 Cu" ion concentration in water samples as measured by the oxygen sensor method and atomic absorption spectroscopy Atomic Oxygen sensor absorption method [Cu"] method [Cu"] Water sample (PPm) (PPm) 0.145 0.150 0.175 0.183 0.443 0.442 0.322 0.333 0.349 0.350 on-site.The possibilities of automating the method will be discussed elsewhere. References 1 Weissberger, A., and Lu Valle, J. E., 1. Am. Chem. SOC., 1944, 66. 700. 2 Grases, F. G.. Forteza, R., and March, J. G., Analusis, 1984,12, 194. 3 Shigematsu, T., and Munakata. M., Bull. Inst. Chem. Res., Kyoto Univ., 1970, 48, 198. Trapping of Radioiodine on Charcoal: Performance and Particle Size Colin G. Taylor, Giles Kay, Duangjai Nacapricha and Michael F. Pimlett School of Chemical and Physical Sciences, Liverpool John Moores University, Liverpool L3 3AF Charcoal, made from coal or coconut shell, which has been activated and impregnated with potassium iodide or triethyl- ene-diamine (TEDA) or both, is used for trapping radioiodine released from nuclear plants.Trapping efficiency is measured as K value [(loglo Vfractional penetration)/stay time] by dosing a bed of charcoal with methyl iodide (iodine-131) under standard conditions. Potassium iodide and TEDA-impregnated charcoals usually exhibit K values in the ranges 4-12 and 10-20 s-', respectively. However, K value measurements on commercial charcoals are often imprecise. This imprecision has been shown to be largely due to the range of particle sizes which can exist in charcoals used for trapping.In the present work, commercial charcoals have been graded by sieving: the K value and some other parameters of the main fractions have then been measured. K values of fractions from 15 KI-impregnated charcoals have been found to increase significantly with decreasing particle size over the range 6-12 US (3.35-1.70 mm aperture). A typical charcoal exhibited reproducible K values ranging from 5.9 (6-8) to 8.9 (10-12). The bed densities of the corresponding fractions ranged from 0.515 to 0.553 g cmP3 and the saturation water contents from The apparent relationship between particle size and porosity 31.1 _+ 0.4 to 33.8 k 0.4y0.~ has been verified by measurements on fractions of an unimpregnated charcoal. Total surface area, macropore volume (mercury porosimetry) and iodine value (I2 uptake) all increase with decreasing particle size.When the same charcoal is impregnated in bulk to a nominal level of 1.5% KI, the level of impregnant in the fractions also increases with decreasing size. The results indicate that, when charcoal is activated, pore structure does not develop uniformly throughout the particles, but is more open in the surface regions than in the interior. Smaller particles with larger surface-to-volume ratios exhibit larger macropore volumes per unit mass, thereby allowing more efficient trapping of radioiodine which, in the K value test, takes place mainly in the macropores (>25 nm radius). Results also confirm that K value precisions are significantly better for graded charcoal samples than for those selected randomly from an over-all batch. References 1 2 Taylor, C.G.. and Griffiths, J. G., Carbon, 1991, 29, 101. Nacapricha, D., Taylor, C. G . , Kay, G., and Pimlett, M. F., RSC Radiochemical Methods Group Young Researchers Meet- ing, University of Salford, September 30th. 1992.ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 429 Use of Thin-layer Chromatography with Flame-ionization Detection to Assess Oil Upgrading During the in situ Combustion Process for Enhanced Oil Recovery D. Price, A. Millington and R. Hughes Department of Chemistry, University of Salford, Salford M5 4W7 The production of heavy oil is inextricably linked to thermal methods by virtue of the dramatic drop in oil viscosity with temperature. In situ combustion (ISC) is more thermally efficient than methods involving steam and can be applied at greater depths, as may be encountered in North Sea reservoirs.It can also be applied to lighter residual oil reservoirs. The process involves burning the heavy fraction of an oil in order to produce the remaining oil. The efficient use of the heavy residual fraction of the oil serves two purposes: (i) to produce and recover the oil, and (ii) to effect substantial upgrading of the heavy components via thermal cracking reactions. The latter could have a significant role to play in reducing the investment and energy requirements for more complex re- finery procedures which will be needed in the future. Unlike many other enhanced oil recovery processes, ISC has demonstrable success. Clearly, this presents a driving force to understand why and where best to apply it.One of the potential advantages of ISC is that of oil upgrading. A programme of research has been initiated to examine the degree and nature of the oil upgrading process. Crude oil is a complex mixture and as such is difficult to define. A variety of techniques have been used to assess oil upgrading, ranging from physical measurements ( e . g . , boiling-point, viscosity) to the identification and quantification of individual chemical species, e . g . , gas chromatography-mass spec- trometry. The latter technique usually provides an over- abundance of data. Class type analyses have also been used, e.g., SARA (Saturates, Aromatics, Resins, Asphaltenes ASTM 4124-86). These seek to provide a simpler measure of the ‘quality’ of an oil.A modern variation on this technique is the use of thin-layer chromatography with flame-ionization detection using an Iatroscan analyser. This technique is faster than the conventional SARA procedure but does not provide samples for subsequent analysis. The programme of research at Salford aims to investigate the nature of various temperature treatments on the SARA composition of an oil and on the pure SARA components. The oil produced by a combustion tube, which is a laboratory-scale model of an oil formation, has also been investigated for evidence of any oil upgrading. Poisonous Exudates of Millipedes C. P. Fairhurst Department of Biological Sciences, University of Salford, Salford M5 4WT Millipedes (Diplopoda) represent the earliest known terrestrial fossils dating from the upper Silurian (Old Red Sandstone) period over 400 million years ago.The characteristic feature of the Diplopoda is that they have fused pairs of segments, allowing twice as many legs as, say, centipedes. This allows a slow but forceful burrowing ability through a metachronal rhythm where six pairs of legs are pushing while one is recovering. They largely feed on decaying organic plant material and are usually surface-active at night because they lack the wax cuticle of, say, insects. Although the fossil record of terrestrial animals is irregular, requiring anaerobic conditions, it is clear that predators were present in the next Devonian era because of spines on each diplo-segment sometimes bi- or trifurcated.By the Carbonifer- ous period these features were being replaced by glands presumably producing, as they do now, defensive secretions. Sometimes these poisons may act offensively as well as in defence. Detailed summaries have been given by Fairhurst,’ Eisner et al. ,2 Witz3 and Hopkin and Read.4 This paper is a precis of these works. Although occasional publications are found earlier, most of the works date from the 1950s with the teams of Eisner,2 Pavan and Woodring and Blum.’ Gland Types and Chemistry The sub-class Pselaphognatha are a small group of soft-bodied animals with no ‘stink’ glands while most of the Diplopoda, the Chilognatha, are hard-bodied and usually have defensive glands and can be grouped into three types. (u) The ‘pill’ millipedes roll into a ball when disturbed and therefore the lateral glands join in the mid-dorsal regions.The exudate is excreted by muscular sacs and is viscous. The chemical components are 172-dimethyl-4( 3H)-quinazolinone and l-methyl-2-ethyl-4(3H)-quinazolinone; these are unique in the animal kingdom and can be lethal to mice and regurgitated by amphibians and birds. It is interesting that similar com- pounds have been found in medicinal plants. The sticky secretion can immobilize ants. Some large tropical species are so well armoured that they have lost the ‘stink’ glands and only a mongoose can crack one by treating it as an egg. (b) The ‘flat-backed, millipedes are modified to have lateral protusions which make them suitable for leaf litter and under bark. Cyanogenic secretions are produced by glands compris- ing two compartments (see Fig.1). In this typical example a precursor, mandelonitrile, is stored in a large sac and on stimulation a retractor muscle is activated and pressure from internal organs forces the chemical into a smaller sac which produces an enzyme to produce cyanide and benzaldehyde. Other chemicals discovered in this group include formic, acetic, isovaleric, myristic, benzoic and stearic acids and phenols. In some cave millipedes the secretion may contain luminous constituents. Note that the orifice is non-pluggable, so the gland is likely to empty totally. Hydrogen cyanide vapour is rapidly absorbed through the respiratory tract and also through surface tissues of predators. A diet of 45 ml 1-’ is fatal for laboratory mice in 2-4 h.Another report indicated430 ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 Mandelonitrile \ 0 / \ CRO yJ+ HCN Benzaldehyde Fig. 1 Diagrammatic representation of the known mechanisms of operations of a flat-back millipede (Apheloriu corruguta Wood). Reproduced from ref. 2 that a large American flat-back had an output capacity of 18 times the lethal dose of a 300 g pigeon and 6 times the lethal dose of a 25 g mouse. There are reports that some primitive Indian tribes use crushed millipedes as poisons for their arrows. (c) The ‘snake’ type millipedes are cylindrical and therefore can be efficient at burrowing into soil or dead trees. There is a non-muscular single gland sac narrowing to an ejaculatory tube with a plug [see Fig.2(a) and ( b ) ] . On stimulation, a retractor muscle acts against a ligament to remove the plug and pressure of body organs aided by struggling and/or curling up exudes the toxins. Note that the plug can be replaced. Some of the tropical species have the ability to spray the toxins by keeping the plug in place until pressure builds up in the gland. Reports of up to 30 cm have been made and in those species that curl up a fountain may be produced, causing blindness in dogs and chickens. The chemical composition always contains a 1,4- benzoquinone and sometimes is combined with a range of other toxins such as 1,4-hydroquinone, trans-dodec-2-ena1, hexa- and octadecanal and o-cresol. Some of these chemicals may be a side product of the cuticular tanning process. The benzoquinones cause eye and skin irritation, circulatory, hormonal and respiratory complains.The LD50 in rats is of the order of 17 mg kg-’. Tropical millipedes may contain up to 350 mg of benzoquinone and the common large millipedes in Britain may contain up to 1.2 mg, sufficient to kill five laboratory rats! (d) Another less well known order of millipede has been reported as exuding p-cresol, which is regarded by some to be the most toxic of the cresols and may be absorbed through the skin, intestinal tract and lungs. The last order to be reported to have an unusual nitrogen-containing monoterpene and a related tricyclic nitro compound, probably obtained from plant material in the diet. Conclusions The effects of these poisons as deterrents may therefore be (a) through skin contact, and with small predators such as ants and 0 r if i ce Fig.2 (a) Diagrammatic representation of a snake millipede (Orthoc- ricas arboreus Sanssure) defence gland and (b) a section through the orifice. Reproduced from ref. 5 mites sticky exudates enhance this effect; (b) through the alimentary canal; (c) through vapour; and (d) with reports of antibacterial and fungal activity. There may also be long-term effects as quinazoline and benzoquinones are strong carcinogens. Indeed the latter are used in artificial form in cancer research. In correspondence with a Zambian surgeon, it emerged that he had linked high levels of throat cancer with villages where large curled up dead millipedes were used as pan scrubbers. There are also reports of intra-specific communications, allowing the remainder of the population to avoid the apparent problem area.There are several reports that the millipede itself may die, probably by blocking of, or inhalation through, the spiracles. There remains an impressive arsenal for such a so-called primitive group to deter potential predators and parasites. References 1 Fairhurst, C. P., Ph.D. Thesis. University of Manchester, 1968, 2 Eisner, T.. Alsop, D., Hicks, K., and Meinwald. J., in Arthropod Venoms (Handbook of Pharmacology No. 48), ed. Bettini. S., Springer-Verlag, Berlin, 1978. pp. 41-72. 3 Witz. B. W., Florida Entomol., 1990. 75, 71. 4 Hopkin, S. P., and Read, H. J., The Biology of Millipedes. Oxford Scientific Publications, Oxford, 1992, pp. 149-157. 5 Woodring, J .P., and Blum, M. S., J. Morphol.. 1965, 116, 99. ch. 5 , pp. 1-20.ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 43 1 Cavity Walls in Solution: New Reagents for Luminescence Trace Analyses in Aqueous Media? John R. Ebdon, David M. Lucas, Ian Soutar" and Linda Swanson The Polymer Centre, School of Physics and Materials, Lancaster University, Lancaster LA1 4YA Recently, we have reported on the capacity of certain water- soluble polymers to sustain phosphorescence from either copolymerized aromatic species' or solubilized aromatic guests2 at ambient temperatures in aqueous media. Introduc- tion of hydrophobic comonomers in copolymerization with species such as acrylic acid (AA) or methacrylic acid (MAA) (which confer solubility in water on the resultant copolymer) affects the hydrodynamic volume of the 'hydrophobically modified' polyelectrolyte (relative to that of the unmodified polyacid) at a given value of pH in a dilute aqueous solution of the polymer.The significance of such hydrophobic influences is discussed below. The ability of hydrophobically modified polyelectrolytes both to solubilize guest species of limited water-solubility and to sustain room-temperature stabilized phosphorescence (~RTSP) from such guests is also addressed. These observations are of importance in consideration of water-soluble solubilizing media for analytical applications. Analytical chemists have explored the potential of solubiliz- ing media such as micellar dispersionss9 and cyclodextrins" in promotion of RTSP in aqueous solution. However, in our experience, the use of such media in routine luminescence analyses can be problematic." In contrast, copolymeric solubilizing media seem to offer significant advantages both in terms of preparative procedures for subsequent spectroscopic examination of analytes and of subsequent system stability and/ or data reliability. Consequently, we have investigated the effects of hydrophobic modification, through copolymeriza- tion, on polyelectrolyte conformational behaviour, with parti- cular regard to analytical applications of RTSP, as described below. Experimental Materials Acenaphthylene (Aldrich) was purified by multiple recrystal- lization (x3) from ethanol followed by multiple sublimation ( ~ 3 ) under high vacuum. Styrene, AA and MAA (Aldrich) were freed of inhibitor and fractionally distilled under high vacuum immediately prior to use. 1-Vinylnaphthalene was synthesised as reported earlier.' Pyrene (Aldrich) was purified by recrystallization from toluene. Thallium(1) nitrate (Fluka) was used as supplied. Statistical copolymers of styrene, acenaphthylene and 1- vinylnaphthalene with AA and/or MAA were prepared by free radically initiated solution (benzene) polymerizations at 60 "C, under high vacuum using 2,2'-azobisisobutyronitrile as initia- tor. The polymers were purified by multiple reprecipitation. Details of synthetic procedures will be reported in due c ~ u r s e . ' ~ . ' ~ Instrumentation Steady-state fluorescence and phosphorescence spectra were recorded using a Perkin-Elmer LS50 spectrometer.Time- resolved phosphorescence measurements were made using a speciallL constructed spectrometer'.'' based on an earlier design. Time-resolved fluorescence anisotropy data were accrued using the technique of time-correlated single photon counting using radiation from the Synchrotron Radiation * To whom correspondence should be addressed. 50 40 E 30 9 20 10 2 4 6 8 10 1: PH Fig. 1 pH dependences of rotational correlation times for the segmental motion of PMAA (0) and an MAA-styrene (20 mol-% in feed) copolymer (M) in dilute (1 x d m ) aqueous solution Source (Daresbury) for excitation. Experimental details will be published elsewhere. '' Results and Discussion Generation of RTSP Polyacids, such as poly(methacry1ic acid), PMAA, and poly(acry1ic acid) , PAA, undergo dramatic changes in hydro- dynamic volume in the pH-induced conformational transition that accompanies neutralization to form the corresponding polysalt.The compact coiled form of the polyacid can accommodate organic guests within its hydrophobic domains. This capacity for solubilization is lost as the polyelectrolyte adopts the expanded, open-coil form of the polysalt. The effects of the conformational change on the chain dynamics of the polyelectrolyte can be studied using the technique of time- resolved fluorescence anisotropy. "-17 Fig. 1 shows the effects of pH on the rotational correlation time, T, (a parameter that characterizes the rate of segmental relaxation of the polyelec- trolyte) , estimated from time-resolved anisotropy measure- ments of the fluorescence emitted by an acenaphthylene, ACE, label (incorporated during copolymerization of 0.5 mol-% of ACE) of PMAA.12 As neutralization of the PMAA is effected, the intramolecular segmental mobility of the macromolecule is enhanced: z, decreases from a value of greater than 50 ns, characteristic of the acid form of PMAA, to less than 10 ns for the completely ionized form of the polyelectrolyte.Fig. 1 demonstrates that, at pH values less than about 4, PMAA exists in its compact 'hypercoiled' form. At pH values greater than about 6, coil expansion is virtually complete. In the latter pH range, the polymer is incapable of solubilizing low molar mass organic species introduced into the aqueous solution. 'Heavy-atom' effects can be used, under appropriate con- ditions, to produce room temperature phosphorescence from aromatic species 'contained' in aqueous media.'-" The heavy atom induces phosphorescence both through promotion of intersystem crossing from the first singlet to the triplet excited432 ANALYTICAL PROCEEDINGS, NOVEMBER 1993. VOL 30 state and through promotion of the radiative deactivation (phosphorescence) of the triplet. We have recently demonstrated the ability of water-soluble polymers to sustain RTSP in occluded guest chromophores.2 In these studies, we have employed the thallium(1) ion as an added promoter of RTSP. However, the ‘dual action’ mech- anism of heavy atom promoters of RTSP is, to an extent, counter-productive in their application to the induction of RTSP in analytes solubilized in polyacids.Promotion of triplet state enhancement via singlet state quenching requires that the heavy-atom quencher gains access to the analyte. Sustenance of RTSP from the triplet created in this step depends, not only on the degree to which it, in turn, is accessed by the heavy-atom species (acting as a promoter of the phosphorescence decay route), but also on the degree of protection which is afforded by the ‘contaminant medium’ for the phosphorescent state of the prospective analyte. Fig. 2 shows the variations in both the intensit and lifetime of the phosphorescence induced by T1+ (1 x 1O-’mol I-*) in a 1-vinylnaphthalene, 1-VN, label of PMAA in dilute aqueous solution. The data illustrate the ‘conflict of interest’ which might be encountered in attempts to use polyacids as solubiliz- ing media for organic analytes in which RTSP is to be promoted using ‘heavy-ion’ species such as TI+.At low pH most of the 1- VN labels will be ‘buried’ within the hydrophobic domains created within the tightly coiled polyacid. Little quenching of naphthyl fluorescence occurs and little phosphorescence is observed (cf. Fig. 2, curve A). As pH increases and the polymer coil expands, the 1-VN labels become increasingly exposed to diffusive encounters with thallium(1) ions, produc- ing a progressive enhancement of phosphorescence from the label. Indeed, at high pH and [TI+] = 1 x mol I-’, fluorescence from the 1-VN label is completely suppressed, phosphorescence being the only emission observable. Unfortu- nately, such a situation is not useful for analytical purposes as the PMAA cannot effect solubilization of organic analytes under these conditions.Examination of the lifetime of the triplet state of the naphthyl label as a function of pH (Fig. 2, curve B) shows the quenching effect of TI+ on this phosphorescent state and the mediating effect of the polyacid on the action of the TI+. At low pH, the relatively small number of triplet states which are created are located in the protective hypercoil. The weak phosphorescence observed is characterized by a mean decay time in excess of 9 ms. As the polymer coil expands under the influence of pH, TI+ ions gain increased access to the triplet states, the latter experiencing enhanced ‘quenching’ (through promotion of radiative decay). At high pH the population of triplet states is characterized by a mean decay time of the order of 1 ms.I I ”?; 7.0 . /A 1500 4 6 8 10 PH Fig. 2 state lifetime (B) as a function of PH. ([TI’] = 1 x lo-* mol I-’) Variation of phosphorescence intensity (A) and mean excited 15 - 10 - 5 - I I I 500 550 600 Wavelengthlnm Fig. 3 RTSP from pyrene (1 X mol 1-’) sequestered in the hydrophobic domains of an AA-styrene (20 mol-% in feed) copolymer induced by TI+ (1 x lo-* mol I-’) at different values of pH Hydrophobic Modification In attempts to overcome the limitations of PMAA and PAA in sustaining RTSP in occluded guests we have investigated the potential of copolymers of MAA and AA with hydrophobic comonomers in analytical applications. It is hoped that such hydrophobic modification will (i) extend the pH range over which solubilization occurs, and (ii) alter the nature of the hydrophobic domains such as to allow RTSP to be generated more readily in solubilization guests.Fig. 1 shows the effects of copolymerization of styrene (20 mol-% in feed) with MAA on the intramacromolecular dynamics of the resultant hydrophobically modified polyelec- trolyte. As pH is increased, the effects of neutralization on the copolymerized acid moieties in promotion of chain expansion are opposed by hydrophobic interactions between the styryl residues. Consequently, the transition from ‘compact to open coil’ behaviour is shifted to a higher pH range than that evident for PMAA itself. As might be expected, the hydrophobically modified poly- electrolyte can effect solubilization of organic guests, such as pyrene, at higher values of pH than can be achieved with PAA or PMAA.Furthermore, the hydrophobic cavities, created within the pH range encompassing that over which chain expansion occurs, appear to be more ‘open’ than the domains that exist in the compact forms of the polyelectrolytes. Fig. 3 shows the relative enhancement of the TI+ (1 x mol I-’)- induced phosphorescence of pyrene (1 x moll-’ in total concentration), solubilized in a styrene-AA copolymer, at intermediate values of pH compared with that observed at low Hydrophobic modification via copolymerization can be achieved using a variety of hydrophobic comonomers. For certain applications, the use of aromatic comonomers in creating the hydrophobic domain has distinct advantages. For example, a copolymer of 1-VN (36 mol-% in feed) and MAA can both solubilize, and sustain RTSP from, pyrene at pH 7.However, the RTSP observed from the pyrene guest is considerably enhanced by excitation of the naphthyl chromo- phores (rather than the occluded pyrene itself) through the agency of energy transfer from the ‘cavity walls’ to the guest. Such ‘energy harvesting’ properties of the polymeric host would be of importance not only in spectroscopic applications but also in the broader general area of enhanced photochemistry. PH- Conclusions Hydrophobic modification produces polyelectrolytes that retain the capacity to solubilize organic species over a more extensive range of pH than that inherent in the parentANALYTICAL PROCEEDINGS. NOVEMBER 1993, VOL 30 433 polyacid.In addition, the hydrophobic domains created at intermediate values of pH in these modified host matrices are more accessible to aqueous-borne heavy-atom quenchers than their highly compacted counterparts in the unmodified homo- polyelectrolyte. These novel systems are capable of sustaining RTSP in occluded organic guests. Consequently, they have potential as a new class of reagent for analyses in aqueous media. References 1 Soutar, I., and Swanson, L., Polym. Commun., 1991,32,264. 2 Soutar. I . , and Swanson, L., Analyst. 1991, 116, 671. 3 Kalyanasundaram, K . , Grieser, F., and Thomas, J. K., Chem. Phys. Lett., 1977, 51, 501. 4 Turro, N. J., Lin, K.-C., Chow, N.-F., and Lee, P., Photochem. Photobiol., 1978, 27, 523. 5 Okubo, T., and Turro, N.J.. J. Phys. Chem.. 1981, 85, 4034. 6 Turro, N. J . , and Okubo, T.. J . Phys. Chem., 1982, 86, 1535. 7 8 9 10 11 12 13 14 15 16 17 Cline Love, L. J., Skrilec, M . , and Habarta, J. G., Anal. Chem., 1980, 52, 754. Skrilec, M., and Cline Love, L. J., Anal. Chem., 1980,52,1559. Cline Love, L. J., Habarta, J. G., and Dorsey, J. G., Anal. Chem., 1984, 56, 1133A. DeLuccia, F. J., and Cline Love, L. J., Anal. Chem., 1984,56, 281 I. Mather, A., Scotland, W. R., Soutar, I., and Swanson, L., unpublished work. Soutar, I.. and Swanson, L., unpublished work. Ebdon, J. R., Lucas, D., Soutar, I., and Swanson. L., unpublished work. Soutar, I . , in Photophysics of Synthetic Polymers, eds. Phillips, D., and Roberts, A. J., Science Reviews, Northwood, 1982, p. 82. Ghiggino, K.P., and Tan, K. L., in Polymer Photophysics, ed. Phillips, D., Chapman and Hall, London, 1985, ch. 7. Bednar, B . , Trnena, J., Svoboda, P., Vijda, S . , Fidler, V., and Prochazka, K . , Macromolecules, 1991, 24, 2054. Soutar, I . , and Swanson, L., Polym. Prepr. (Am. Chem. SOC., Div. Polym. Chem.), 1992, 33, 828. Pinks and Blues A. Atkinson Atkinson Chemicals Ltd., 23 High Street, Twyford, Reading, Berkshire RG I0 9AB The use of water as a heat and energy transfer medium is commonly accepted without much excitement. However, water and its chemical treatment is one of the most rewarding and involved subjects that a chemist can get involved in. The aspects of water chemistry are diverse and overlap with other scientific disciplines, e.g., engineering and biology.Water finds favour owing to its physical characteristics of good heat capacity, heat transfer properties, low toxicity, availability and acceptable cost. It is well known that if mild steel is submerged in soft ‘Manchester’ water that corrosion very soon becomes apparent. Similarly, people accept that washing in ‘London’ water gives rise to scum formation. These two very simple observations open discussion on how to avoid the injurious effects of corrosion and scale in manufacturing output. Intrinsic to the two aspects mentioned is microbiology: bacteria, fungi and algae. These organisms play an important role in water treatment, especially in cooling waters. Probably the most recognized and emotive of bacteria that ‘the man in the street’ is aware of is the genus Legionella.The isolation of this bacterium and its fatal potential in some humans has led to a resurgence in the study of water treatment, with closer attention being devoted to chemical monitoring and control. It has also promoted a whole new growth sector related to cleaning and sterilization. There are numerous analytical tests available for the monitoring of the broad spectrum of chemical additives used in the water industry, in addition to the routine tests to generate data about the naturally occurring salts dissolved in water. It is the dissolved salts and gases that determine the behavioural pattern of a particular water in respect of its corrosive or scale- forming potential; it is the water technologist’s skills that interpret the analytical results and devise a suitable chemical treatment programme to ensure plant operates efficiently.Thousands of chemical tests are carried out each day by hundreds of people involved in the water industry. Very rarely are there any laboratory facilities and the tops of 200 1 drums or window ledges have to suffice as work tops. Boiler water, cooling water, heating and chiller circuits are the prime water systems that are regularly monitored. To illustrate the chemistry used and the on-site ‘wet’ chemistry methods adopted, a selection of tests are described from the boiler and cooling water sectors. Boiler Water Treatment The basic function of a steam raising boiler plant is to convert the latent calorific energy of oil, coal, wood, gas, etc., into a more usable and manageable form, i.e., steam.As experienced during the early period of industrial boiler use, if care is not taken about the water chemistry and boiler design the unit can become a danger, with explosions a common occurrence. Today the chemistry is well understood but fatal accidents still occur. It is important that scale deposition and corrosion activity are kept within acceptable limits. The monitoring and mainten- ance of concentrations of selected chemicals therefore become important aspects of any water treatment programme. Corrosion (Related to Dissolved Oxygen) To avoid corrosion activity in a boiler plant necessitates the removal of dissolved oxygen from the boiler feed-water. This is achieved in two ways, the first of which is the application of Henry’s Law of inverse gas solubility versus water tempera- ture.This physical property is put into practice in most boiler plants by a good boiler feed-tank design, which effectively utilizes the density differential between hot and cold water to obtain good mixing, hot water being dissipated in the lower regions of the feed-tank and cold water at the top. The second method is the use of chemical reducing agents. The choice of chemical will be from: sodium sulfite (usually catalysed with a cobalt salt), tannins, sodium erythorbate, diethyl hydroxylamine (DEHA), methyl ethyl ketoxime (MEKO), hydroquinone and hydrazine (now only used in the more sophisticated plants). Sodium sulfite scavenging occurs in accordance with the stoichiometric reaction: 2s032- + 0 2 3 2s042- (1) The S032- reserve is measured using standard potassium434 ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 iodatehodide, titrating the released iodine with a standard solution of sodium thiosulfate [see eqns.(2)-(4)J. 5s032- + 2103- + 2H+ -+ 5S042- + 21- + H20 (2) 1 0 3 - + 51- + 6H+ + 312 + 3H2O (3) r2 + 2 ~ ~ 0 ~ ~ - + + 21- (4) Tannin chemistry introduces the properties of polyhydrics offering phenolic groups in ortho or para positions. Gallic acid is just one of the polyhydrics that is formed on tannin hydrolysis. This molecule exemplifies the chemical reactions as shown in eqn. (5). COOH I COOH II OH 0 This reaction is comparable to the laboratory use of alkaline pyrogallol and hydroquinone as oxygen scavengers [see eqn. (611- OH 0 OH 0 Tannins give a brown coloration to the water which limits the choice of indicator.The problem is solved by using the strong coloration of the titrant itself, namely potassium permanga- nate. The end-point is reached with the first permanent purple colour. Sodium erythorbate, DEHA and MEKO are becoming more commonly encountered in boiler water treatment. The last two compounds are also steam volatile and give assisted corrosion protection to the condensate system. The monitoring is carried out using a colorimetric procedure involving the formation of an organoiron(1r) salt. The organic reagent used is FerroZine which forms metal complexes with iron but only Fe". FerroZine is the disodium salt of 3-(2-pyridyl)-5,6-bis(4- phenylsulfonic acid)- 1,2,4- triazine. A standard solution of an iron(rr1) salt is added to the sample of water to be analysed.The resultant iron(r1) concentration is then in direct proportion to the organic reducing agent present in the sample. The Fe" ion is then complexed by the FerroZine and the colour density measured using a Lovibond calibrated disc. The method is very sensitive and gives accurate results down to 0.1 mg 1-l of Fe, see Fig. 1. Corrosion (as a Result of Dissolved Carbon Dioxide) In respect of condensate line corrosion this is caused by the presence of the dissolved gases oxygen and carbon dioxide. If the oxygen scavenging programme is working effectively then there is only the 'acid attack' to be rectified. Acid attack originates from the calcium (sodium if a base exchange water softener is installed) hydrogencarbonate in the boiler feed-water.The effect of heat on this anion causes thermal breakdown to carbonate and release of CO2. Under boiler conditions the C032- undergoes hydrolysis to OH- with further generation of C02 [see eqns. (7) and (S)]. 2HC03- --+ C032- + C02 + H20 (7) heat C032- + H20 -+ 20H- + COz (8) As the C02 dissolves in the condensing steam a series of equilibria are set up: 2CH3CC2H5 + 4Fe3+ + H20 -2CH3CC2H5 + 4Fe2+ + 4H+ + N20 II n NOH 0 s-0- 0 A Fez+ U[-.- 0 FerroZine iron (11) salt Fig. 1 Test for organo-reducing agents using MEKO as example C02 + H20 H2CO3 H+ + HC03- (9) Carbonic acid attack is readily identified since the tube conveying the condensate becomes noticeably thinner in the lower regions. Pipe perforations are common with threaded joints often suffering first, being the thinnest metal parts.It is no fun being hit on the head with drops of scalding water from a perforated overhead steam condensing air heater! The corrective chemical action taken on most occasions is to use neutralizing steam-volatile amines. Those in common use include: cyclohexylamine, morpholine, 2-aminomethylpropa- nol, diethylaminoethanol and ammonia. The simple test procedure for neutralizing amines is to check that the returning condensate pH is S . 0 . An alternative to volatile amines is the direct injection into the steam header of long-chain aliphatic amines, often referred to as filming amines. As the name implies, filming amines offer their protection by the formation of a protective hydrophobic film on the condensate pipework. Octadecylamine, in an emulsion form, is the most common fatty amine used. A concentration of 1 mg 1-' in the condensate return is the target figure for confidence that the desired protection is being achieved.This concentration can be measured using a test based on the reaction between sulfonphthaleins which, in contact with primary, secondary or tertiary amines, produce a yellow colour, the density of which is related to the amine content in the sample. The generated colour is extracted into chloroform, after which the colour density is measured against a standard Lovibond disc. The indicator used is tetrabromo-m- cresol sulfonphthalein, Bromocresol Green. Although the Lovibond glass standard is calibrated specifi- cally for octadecylamine other amines can be monitored using the same technique by calculating the appropriate conversion factor thus: Conversion factor = M , of test amine No.of amine groups X M , of octadecylamine (10) Cooling Water Additives The cooling water treatment sector offers a host of remedial chemical opportunities for the inhibition of corrosion, scaleANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 435 and biological contaminants and the removal of suspended solids. Chemical choice includes both inorganic and organic molecules to achieve the desired plant operating efficiencies. The initial information gleaned from a water sample is the ‘Pinks and Blues’. This refers to the acid-base titration using 0.01 mol I-’ H2S04 as the titrant and the indicators phenol- phthalein, pink, referenced as the ‘p’ value and screened methyl orange, blue, referenced as the ‘rn’ value.These tit ra tion values give informa tion about the h ydrogencarbona t e concentration which is invaluable in cooling water technology. The phenolphthalein value is of much greater importance in boiler water treatments, see Fig. 2. The calcium and magnesium ion concentrations complete the initial profile of a water and from these data the ‘in-use’ plant behaviour of the water can be predicted and a suitable chemical programme proposed. Calcium and Magnesium The determination of calcium and magnesium adopts the chelating properties of ethylenediaminetetraacetic acid (EDTA); tests are carried out under different alkaline buffer conditions and with various indicators.( a ) To test total hardness the following conditions are employed: buffer solu- tion, ethanolamine hydrochloride, pH 10.5; indicator, Erio- chrome Black T [( l-hydroxy-2-naphthylazo)-6-nitro-2-naph- thol-4-sulfonic acid]. Eriochrome Black T forms metal complexes with both calcium and magnesium ions. In its uncomplexed form it is blue, and as a Ca/Mg complex it is red, see Fig. 3. (6) To test calcium hardness the following conditions are employed: buffer, sodium hydroxide , pH 12+ [precipitates Mg as Mg(OH)2]; indicator, Patton and Reeders reagent [2-hydroxy-l-(2-hydroxy-4-sulfo-l-naphthylazo)-3- naphthylic acid]. The reagent uncomplexed is blue, while the reagent complexed is red, see Fig. 4. The inorganic salt that has to be given close attention is calcium carbonate, since this is the most likely salt to precipitate from solution, especially in the hotter regions [see eqn- (1111 Ca(HC03)2 e CaC03 + H20 + C02 (11) To establish an understanding of the above equilibrium the values of pH, [Ca], rn alkalinity and temperature are substi- tuted into equations initially derived by Langelier.Ryznar‘ has subsequently put a more practical interpretation on the l4 2 12 c I 8 1 \-‘p‘ alkalinity 2 t Volume of 0.01 mol I-’ HzS04/ml Fig. 2 Acid-base titration of cooling water sample. Alkalinity is recorded as CaC:03 concentration (rng 1-’). When p = 0*, m = HCO3-, ie., alkalinity present is due to the presence of hydro encar- bonate ion only. When p < fm*, denotes presence of CO$- and HCO3-; 2 x p value = C03’- concentration present, m - C03’- = HCO3- concentration present.When p > bm. denotes the presence of CO3’- and OH-; 2p - m = OH- concentration present, p - OH- = C O ~ ~ - concentration present. Whenp = m, denotes that all alkalinity is present as hydroxide. The asterisk indicates cooling water values Ca2+ + Mg2+ + EDTA4- - EDTACa2- + MgZi 0 /r\ 0 + EDTA4- so3 - Eriochrome Black T Mg complex (red) ?- I ?- SO3- Eriochrome Black T (blue) Fig. 3 Total hardness titration ca2+ + Mg2+ + 20H- -Ca2+ + Mg(0H)Z o\cP- 0 Patton and Reeders reagent Ca complex (red) o* p- C 0- 0- m N = N m S 0 3 - \ / + [EDTACaIz- \ / Patton and Reeders reagent (blue) Fig. 4 Calcium hardness titration calculated values. The recorded numerical ratings are referred to as the Langelier and Ryznar indices, respectively, with the actual value giving an indication of the severity of the foreseeable problem, see Fig.5. Organic Additives There is invariably an organic component in any water treatment programme, whether as a corrosion inhibitor, anti- scalant, dispersant, biocide, etc. The structures of some organics typically used are shown in Figs. 6 and 7; sulfonated organics are also used. Corrosion Corrosion inhibitors basically interfere with the flow of electrons in the two half-cell electrochemical processes. They are normally classified in one of the following categories: anodic, e . g . , orthophosphate, nitrite, chromate, silicate; cathodic, e . g . , zinc salt, calcium hydrogencarbonate, calcium phosphonates; adsorption, e.g., fatty amines, some carboxylates.As the name implies, the chemical inhibitor has the ability to react with, or in some way affect, the products of a particular half-cell reaction. At the anode there is an oxidation reaction,436 ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 3 2.0 1.0 0 -1.0 -2.0 -3.0 Scale-forming Corrosion tendency tendency Langelier index - 3.0 -6.0- 9.0 Scale Corrosion Ryznar index Fig. 5 Prediction of the behaviour of cooling water Poly(acry1ates) coo- l I I coo- coo- -CH2-CH-CH2-CH-CH2-CH-CH2- Poly( methacrylates) CH3 CH3 CH3 I I I -CHZ-C -CH2-C-CH2-C-CH2- I I I coo- coo- coo- Poly(ma1eates) (simplified version) coo-coo- coo-coo- I I I I -CH- CH- CH-CH- CH-CH-CH -CH - I I coo-coo- I I coo-coo - Styrene-maleic acid copolymer (also sulfonated styrene- maleic acid copolymer) coo-coo- coo-coo- I I I I -CH2 -CH -CH -CH-CH2-CH-CH -CH- I I C6H5 C6H5 Poly(acry1ate) AMPS derivatives L Fig.6 Polymeric organic compounds used as additives in cooling water. AMPS = Aminomethylpropanesulfonic acid where a metal converts to metal ions. Anodic inhibitors thus block the anodic reaction by the formation of an insoluble deposit, e.g., iron phosphate, iron silicate, iron oxides. At the cathode there is a reduction reaction, concerned primarily with the reduction of oxygen and subsequent formation of hydrox- ide ions. Thus, cathodic inhibitors react with hydroxide to produce insoluble protective deposits depriving the access of oxygen to the cathode, e.g., eqn. (12): Zn2+ + 20H- --+ Zn(OH), (12) ATMP Aminotris(methy1enephosphonic acid) HEDP Hydroxyethylidenediphosphonic acid PBTC 2-Phosphonobutane-l,2,4-tricarboxylic acid CH2COOH I HOOC-C-PO3H2 I CH2 CH2COOH I HPA Hydroxyphosphonoacetic acid HO-CH-CH2COOH I P03H2 PPA .Phosphinopoly(acrylic acid) 0 -p:;cH2~qcH2-:Fig.7 Organic compounds used as additives in cooling water Zinc is never used alone since its performance is not acceptable. It is always used in conjunction with either an organic or polyphosphate, with the former being most likely in current formulations. Organic additives have two effects regarding the use of zinc as a corrosion inhibitor. The choice of polycarboxylate can have an influence on the zinc hydroxide precipitation pH, an important and desirable feature in some waters, whilst phosphonates improve the protective zinc hydroxide film.Zinc is often used to monitor a (zinc- containing) corrosion inhibitor using dithizone as the indicator. A normal zinc reserve would be 2-3 mg I-', see Fig. 8. Sodium nitrite has been known for several decades to be an excellent corrosion inhibitor for the protection of mild steel. The chemical still continues to find application today, but, to a lesser extent, due to discharge limits. This has partially been overcome by the development of synergized formulations of nitrite in combination with selective organophosphonates that permit a ten-fold decrease in nitrite concentrations. Sodium nitrite is still used in both chiller and hot water circuits. Its efficiency is well established when used at the correct concentration; should the concentration fall below the desired reserve then serious pitting corrosion will occur.This treat- ment serves as an excellent example of the importance of competent and regular monitoring. Monitored sodium nitrite concentrations are typically loo0 mg I-', although with synergized sodium nitrite products the concentration (as NO2-) can be as low as 40 mg 1-1 in open evaporative cooling water circuits and 100 mg I-' in closed systems. Sodium nitrite is measured using the oxidative properties ofANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 437 IZnDTPAl- Fig. 8 Determination of zinc. Titrant, N, N , N’, W,W-diethylene- triaminepentaacetic acid (DTPA); indicator, dithizone; buffer, ace- tate, pH 4.5; concentration range 1-5 mg I-’ 1 ,lo-Phenanthroline Iron(ll) complex [Fe(Cl2H8N2l312+ REACTIONS X e 4 + + NO2- + H20 - Xe3+ + NO3- + 2H’ [Fe(C12H8N2)312+ + Ce4+ - Ce3+ + [Fe(Cl2HsN2)3l3+ Blue Red Fig.9 Determination of nitrite. Titrant, cerium(1v) sulfate; indicator, 1 ,lo-phenanthroline-iron complex (ferroin); concentration range, 40- 2000 mg I-’ Ce4+ and the clear end-point shown by the indicator iron(i1) ortho-phenanthroline, ferroin, see Fig. 9 and eqns. (13) and 2Ce4+ + NO2- + H2O +- 2Ce3+ + N03- + 2Ht (13) (14) - [(C12H8N2)3Fe]2’ + Ce4+ -+ [(C12H8N2)3Fe]3+ + Ce3+ deep red pale blue (14) Phosphonate Monitoring Most of the organophosphorus compounds shown in Fig. 7 act as good chelating agents and react favourably with Th4’. A sample of cooling water (this method is also convenient for phosphonate monitoring in boiler water treatments) is titrated with a standard solution of thorium nitrate using xylenol orange as indicator, see Fig.10. Determination of Anionic Polymers The testing of anionic polymers provides a further example of the wide range of chemistry that has been adapted in order to monitor a particular chemical. This technique utilizes the interaction between anionic and cationic polymers. The molecular weights of anionic polymers used in cooling water fall in the range 1000-5000. In the presence of a high molecular weight cationic polymer, charge neutralization occurs and precipitation results. The turbidity produced reflects the concentration of anionic polymer present. Cetylpyridinium chloride is the cationic polymer commonly used. CH2COOH CH2COOH Th4+ + [phosphonatel- -[Th phosphonate14- Th4+ + [xylenol orangel- Y [Th xylenol orange14- Y Fig.10 Determination of ‘phosphonates’. Titrant, thorium nitrate; indicator, xylenol orange (screened); concentration range, 2-15 mg I-’; pH, 2.5-3.0 100 90 8 80 z 70 60 5 50 40 30 I= 20 3 10 - - v1 3 r .c 4- .- v) m .- 0 7.0 8.0 9.0 10 PH Dissociation (HOX S H+ + OX-) curves of hypobromous Fig. 11 acid and hypochlorous acid (X = Br or Clj - H / \ H H DPD Red Colourless Fig. 12 Oxidative reactions of DPD. The formation of fairly stable free radicals gives rise to the red coloration, known as Wurster’s dyes. Developed colour is measured in a visual colour comparator. Excess of oxidant produces the colourless ‘quinoid’438 ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 Hypochlorous and Hypobromous Acids The emotive subject of Legionaires’ disease has led to a tighter control of system water testing, reporting and recording.It has also prompted a requirement for cooling circuit sterilizations to be carried out biannually. The actual Legionella bacterium is of a pneumonia type and has to be inhaled to cause any physical harm. The problem with cooling towers is that there is a ‘drift loss’ from the top of the cooling tower. If the atmospheric conditions are such, or the tower is close to a building’s air intakes, then the water droplets may be inhaled by an unsuspecting victim. Apart from its use as a cleanerkterilant chlorine (hypochlorite) can also play a part in a continuous biological control programme. If the planktonic bacteria count is zero in the cooling water then even if any aerosols from the drift losses should be inhaled there would be no potentially fatal Legionella bacteria present. Many cooling waters operate at pH values in excess of 8.0 and the performance of ‘chlorine’ deteriorates at higher pHs.This is because of the ionization of HOCl (which is the killing species), OC1- ions having a very limited biocidal effect. In recent years this has been overcome by the introduction of hypobromous acid, generated either from bromine release compounds or from the addition of sodium bromide to hypochlorite solutions. Hypobromous acid is a much weaker acid and dissociates significantly less than hypochlorous acid, it is thus a better biocide used at equivalent dosage concen- trations at higher pHs, see Fig. 11. Two methods of testing are employed depending on the concentration oxidant in use.In sterilization work the moni- tored chlorine reserve will be in the range 15-50 mg 1-l and at this high dosage the colour generated by the formation of iodine, following the addition of potassium iodide, can be measured using a standardized glass and a Lovibond compara- tor. With regard to on-going halogen usage in an evaporative cooling water system where the free halogen concentration is about 0.2 mg l-’, control is monitored by treating free halogen with N, N-diethyl-p-phenylenediamine (DPD No. 1). The density of colour produced is measured against standard coloured glasses, see Fig. 12. Conclusion All of the examples described above, and many more, are present in the service engineer’s test kit.Modem test kits are compact using accurate trigger operated digital titrators (replacing burettes) or alternatively using specially designed ‘drop’ bottles which deliver a standard size drop on every occasion. In some instances the standard titrant may be in tablet form. This paper has only sought to give an insight into water treatment and some of the tests that are used daily. It is hoped that it has achieved the aim of showing water treatment to be a subject of scientific substance. The examples described have only considered inorganic and organic chemicals, no consider- ation having been given to the subject of biological testing. References 1. Langelier, W. F., AWWA J., 1936, 28, 1500. 2. Ryznar, W. J., AWWA J., 1944, 36, No. 4. On-line Immobilized Chelating Agents in Flow Injection Systems G.M. Greenway and A. Townshend School of Chemistry, University of Hull, Hull HU6 7RX The incorporation of chelating groups into polymers or other materials provides stronger metal ion bonding than conven- tional ion exchangers and, in some instances, more selective metal ion pick-up can also be achieved. Such chelating materials have attracted particular interest due to their ability to preconcentrate metal ions from very dilute solutions, thus allowing detection limits to be greatly improved. *-' Such insoluble chelating agents have been extensively investigated for use in flow injection systems as mini-columns for on-line preconcentration of metal ions prior to determination by, for example, atomic absorption ~pectrometry,~,~ chemi- luminescence emissions,9 or ion-selective electrode potentiometry. lo Various supports have been used for the chelating groups, such as styrene-divinylbenzene copolymers, cellulose, silica gel and Sepharose.However, in the work described in this paper, controlled-pore glass particles have been used, because they do not swell when placed in liquids and have a large surface area. Various chelating groups have been bound to the glass surface. For example, the following reaction has been used to produce a dithiocarbamate derivative: to' To immobilize quinolin-8-ol-5-sulfonic acid chloroquinolin-8-01) , l3 a reaction has been somewhat different to that used previously:' (HQS)12 (or 6- used which is iHNO' Dithizone has been immobilized similarly, l4 and cysteine has been attached via a trie t hox y aminosilane-glu taralde hyde reaction. l3 Mini-columns (2 mm x 4 cm) were used to incorporate the chelating material in a flow injection system, such as that shown in Fig.1. Samples of 5 or 10 ml were passed through the column, after which the accumulated metal ions were eluted by injection, usually, of 100 pl of dilute nitric or hydrochloric acid. In this way, detection limits were improved by 2-3 orders of magnitude (Table l), whilst retaining good reproducibility. As expected, because some time is required for the sample to flow completely through the column ( e . g . , 2.5 min for a 5 mlANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 De-ionized water Metal ion solution 1 I 3 4 5 - 2 ml min-' n HN03 439 To waste Fig.1 valve; 4, column of immobilized reagent; and 5 , atomic absorption spectrometer Flow-injection manifold for the preconcentration of metal ions by the immobilized reagent. 1,3-way valve; 2, peristaltic pump; 3, injection Table 1 Comparison of detection limits and metal ion uptake capacity for various insoluble chelating materials Detection limithg ml-'* Metal ion Cd2+ co2+ cu2+ Hg2+ Pb2+ Zn2+ Di t hio- HQS carbamate Dithizone Cysteine 0.6 - - 0.1 0.5 2 - 0.8 0.5 0.05t 0.1 0.1 lot 101 - - 2.0 1 - 0.1 0.2 25t 507 10 Selenestrum HQS 0.2 7.8 8 1.4 0.05 5.0 30 5.6 2.5 5.7 0.2 8.1 Uptake capacity/mmol g-' * Determination of flame atomic absorption spectrometry; 5 ml of sample; 100 p.1 of eluent. 1 10 ml sample. Dithio- carbamate Dithizone Cysteine Selenestrum - - 11.7 11.7 4.3 - 5.5 2.5 4.6 7.3 7.9 9.7 3.9 1.5 8.9 1.6 - - 12.5 11.4 - - 8.0 8.4 sample), the preconcentration procedure has a throughput of only 20 h-' compared to 150 h-' for the direct injection method.I' It is particularly noteworthy that the capacity values (usually >5 mmol g-') are very high, compared with values for quinolin-8-01 immobilized on silica gel of about 0.3 mmol g-',I5 and the values for many other chelators. An even more interesting development has been the use of immobilized organisms for metal ion preconcentration. Naka- jima and Sakaguchi,16 for example, investigated the precon- centration of metal ions by each of 83 micro-organisms immobilized in polyacrylamide gel. Binding is su ested to be to cell walls via amine, carboxyl and thiol groups.@18 It is only very recently, however, that such materials have been used in preconcentration for ultra-trace analysis, and not in immobil- ized In this laboratory, two organisms, Selenestrum capricornulum2' and Chlamydomonas reinhartii have been immobilized on controlled-pore glassI3 by the aminosilane- glutaraldehyde method. The detection limits and capacities (Table 1) are similar to those obtained by the immobilized ligands and the capacities are similarly high.A study of metal interferences in the on-line preconcen- tration systems yields interesting results. As the chelating materials have such a high capacity, they should readily accommodate the cobalt content from, say 5 ml of 0.5 pg ml-' cobalt solution plus other metal ions, e.g., at 20 pg ml-'.Thus there should be no interference of one metal ion on another with respect to preconcentration in an equilibrium situation; there is sufficient capacity to preconcentrate several metal ions at the trace level. Moreover, on subsequent elution, the co- eluted metal ions will not mutually interfere in their determi- nation by atomic absorption spectrometry. In many instances, this expected absence of interferences has been demonstrated. For example, in the determination of copper in a 0.12 pg ml-' solution using the dithiocarbamate chelator, the presence of 10 Fg ml-' Cd2+, Pb2+, Zn2+ or Co2+ has no effect. Likewise, with the use of the immobilized cysteine for the determination of 1 pg ml-' Pb2+, 10 pg ml-' Cu2+, Zn2+, Co2+, Hg2+, Cd2+ or Mg2+ were without effect.However, for the quinolin-8-01 derivatives and for Selenestrum, significant interference effects are observed. For example, in the determination of 0.1 pg ml-' Cd2+ using HQS, 20 pg ml-' Cu2+ depresses the signal by 18%, 20 pg ml-' Co2+ by 22% land 20 pg ml-' Zn by 20%. For the determination of 50 ng ml- Mg2+, the depressions by 10 pg ml-' of the following ions are ve large: Cd2+, 63%; Pb", 60%; Cu2+, 78%; Zn2+, 84%; C 2 + , 94%. Such effects have been observed previously' and must arise from a relatively slow interaction of the metal ions with the chelating material. Thus, in the flow system competition is set up between metal ion species for reaction with the ligands in the limited time available as the solution passes through the preconcentrator.This seems to be an interesting kinetic phenomenon, and it is currently being studied in some detail. 1 2 3 4 5 6 7 8 9 10 11 12 13 References Hirsch, R. F., Gancher, E.. and Russo, F. R., Talanta, 1974, 17, 483. Fridman, Ya. D., and Dolgashova, N. V., Zh. Anal. Khim., 1970, 25, 26. Tanaka, H., Chikuma, M., Hirada, A., Ueda, T., and Yube, S., Talanta, 1970, 23, 489. Vernon, F., and Nyo, K . M . , Anal. Chim. Acta, 1973,93,203. Verma, F . , Sep. Sci. Technol., 1978, 13, 273. Olsen, S., Pessenda, L. C. R., RfiEiCka, J . , and Hansen, E . H., Analyst, 1983, 108,905. Malamas, F., Bengtsson, M., and Johansson, G., Anal. Chim. Acta. 1984, 160, 1. Sakamoto-Arnold, C. M., and Johnson, K. S . , Anal. Chem., 1987, 59, 1789. Al-Warthan, A. A., Habib, K. A. J . , and Townshend, A., Fresenius' J .Anal. Chem., 1990, 337, 848. Risinger, L., Anal. Chim. Acta, 1986, 179, 509. Townshend. A., and Habib, K. A. J., Microchem. J . , 1992,45, 210. Devi, S., Habib, K. A. J . , and Townshend, A., Quim. Anal., 1989, 8 , 159. Elmahadi. H. A. M., Ph.D. Thesis, University of Hull, 1992.440 14 Habib, K. A. J., Ph.D. Thesis, University of Hull, 1991. 15 Marshall, M. A., and Mottola, H. A,, Anal. Chem., 1985, 57, 729. 16 Nakajima, A., and Sakaguchi, T., Appl. Microbiof., 1986, 24, 59. 17 Hosea, M., Greene, B., McPherson, R., Henzl, M., Alex- ander, M. D., and Darnall, D. W., Inorg. Chim. Acta, 1986, 123, 161. ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 18 19 20 21 Crist, R. H., Oberholser, K., Shank, N., and Nguyen, M., Environ. Sci. Technol., 1981, 15, 1212.Majidi, V., and Holcombe, J. A., Spectrochim. Acta, Part B , 1988, 43, 1423. Majidi, V., and Holcombe, J. A., J. Anal. At. Spectrom., 1989, 4,439. Elmahadi, H. A. M., and Greenway, G. M., J. Anal. At. Spectrom., 1991, 6 , 643. Applications of Trace Metals Analysis at ICI Specialties Research Centre Sharon C. Stephen ZENECA Specialties, Specialties Research Centre, P. 0. Box No. 42, Hexagon House, Blackle y, Manchester M9 3DA The presence of trace metal impurities can be detrimental to the quality of a product and may, in some instances, have important environmental implications. During the last few years the Inorganic Analysis team within the Analytical Sciences Group at ICI Specialties Research Centre, has carried out a number of projects involving the identification and quantification of trace metal impurities in some dyes and other products.Two such applications are discussed in this paper. Determination of Chromium(i1) and Chromium(vr) in Dyes For some metals, the species of the metal is more important than the total concentration, e . g . , chromium and mercury. Suitable procedures have been developed to determine the free chromium content in the chromium complex dyes range. Of particular interest was chromium(vi), which is a suspected carcinogen. Both Cr"' and CrV1 were expected to be in the low parts per million concentration range. In total, three methods have been developed owing to the complexity of the separation of free chromium species from the water-soluble chromium dyes. Initial work involved the simultaneous determination of chromic and chromate using a chromatographic separation with visible detection.The Cr"' was complexed with pyridine- dicarboxylic acid (PDCA) using a boil-up procedure to accelerate the reaction. The dye and chromium species were separated chromatographically using a Hypersil ODS column and a tetrabutylammonium hydroxide eluent adjusted to pH 6.75 with phosphoric acid. Detection at 380 nm was used, which was a compromise between the absorbance maxima for the Cr"' complex and CrV' complexes. The method was successful for the analysis of a number of the dyes; however, problems were encountered with some dyes due to coelution of impurity species with the Cr"' and CrV'. An alternative detection system using flame atomic absorption spectrometry (FAAS) was evaluated.Obviously FAAS would respond only to chromium-containing species. The outlet of the chroma- tography column was connected directly to the nebulizer. The sample preparation procedure using complexation with PDCA was no longer necessary for AAS detection and a simplified procedure was adopted whereby a 1% m/v aqueous dye solution was prepared. The Cr"' was detected as the cation on the solvent front. The eluent system was similar to that previously employed but was prepared from tetrabutylam- monium sulfate and adjusted to pH 6.75 using sodium hydrox- Table 1 Parameters for determination of C I " and Crv* in dyes Chromatographic conditions- Column Pump rate 2 ml min-' Injection volume 200 pl Eluent 25 X 4.6 cm Hypersil ODS 80% 10 mmol I-' tetrabutylammonium sulfate adjusted to pH 6.75 with sodium hydroxide -20% acetonitrile Detector wavelength 380 nm Flame atomic absorption conditions- Instrument Instrumentation Laboratory, Model 451 Wavelength 357.9 nm Bandwidth 1 nm Flame Nebulizer uptake rate 2 ml min-' Lamp current 6 mA Air-acetylene; fuel rich with eluent, stoichiometric without eluent ide.This procedure was adopted following recovery experi- ments where Cr"' could not be retrieved. Inspection of solubility data suggested that sparingly soluble chromium(n1) phosphate was formed. The retention time for CrV' was 3.5 min. Chromatographic conditions and FAAS instrument settings are given in Table 1. Limits of detection using the procedure are 40 pg g-' for Cr"' and 20 pg g-' for CrV'.This procedure was used to analyse over 50 chromium complex dyes. No CrV' was detected in any of the dyes. Following results and conclusions from the analysis of the dyes using the previous method, a third, more simple procedure was developed to measure total free chromium in the dyes. The dye was mixed with cetyldimethylammonium bromide and added to a 30 cm length of dialysis tubing with de- ionized water. The tubing was sealed at both ends and placed in a screw-top glass bottle containing de-ionized water and left for 48 h. The chromium dye forms an ion pair with the cetyldi- methylammonium bromide and prevents permeation through the dialysis tubing. Any uncomplexed chromium species will equilibrate in the tubing solution and the de-ionized water. The total chromium in the water was measured by either FAAS or by inductively coupled plasma atomic emission spectrometry (ICP-AES) .Trace Impurities in Copper In some instances the presence of contaminant metals is detrimental to the quality and properties of the product. ForANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 Table 2 Analysis of SRMs 394 and 395 by FI ICP-MS* SRM 394 SRM 395 Element Found Certified Found Certified Fe 71 147 86 96 As 7.0 2.6 5.0 1.6 Ag 86 51 27 12.2 Sb 3.6 4.5 7.6 8.0 Pb 2.5 26.5 3.3 3.25 Bi 0.28 0.35 0.44 0.5 * All values in pg g-' . example, trace metal impurities affect the electrical and physical properties of copper and limits for these are prescribed by the American Society for Testing and Materials (ASTM).* A method was required to measure arsenic, antimony, bismuth, iron, lead and silver in washed copper.Procedures used to measure metals in copper include spark emission spectrometry; however, as this technique was not available procedures were developed using inductively coupled plasma mass spectrometry (ICP-MS). A number of approaches were evaluated,2 including the direct nebulization of copper solu- tion, flow injection (FI) and removal of the copper solution using solvent extraction. The work was carried out on a VG PlasmaQuad PQ2 Turbo Plus ICP-MS instrument. Indium was added to all solutions at 10 ng ml-' as an internal standard. To study the effect of the direct nebulization of a copper solution, a 0.2% m/v solution of copper was used. Spectra were acquired at 5 min intervals over a 2 h period. A major reduction in signal intensity with time was observed for all elements, although some improvement was observed for Ag, As, Fe and Sb by ratioing the signal to the internal standard. The ratioed intensities of Pb and Bi were found to increase with time. The experiment was repeated by aspirating a 1% v/v nitric acid solution between sample measurements. No im- provement in signal stability was observed. -Flow injection is used for the analysis of samples with high dissolved solids and similar intensity versus time plots were obtained using 500 p1 injections of the 0.2% m/v copper solution in a dilute nitric acid carrier stream. Significant improvements in signal stability were obtained using flow injection. The procedure was validated using National Institute of Standards and Technology (NIST) copper Standard Refer- ence Materials (SRMs) 394 and 395 and the results are shown in Table 2. Good agreement between the certificate results and the flow injection results for Bi, Pb and Sb was observed; however, poor agreement was obtained for Ag, As and Fe. It is 441 Table 3 Analysis of SRM 395 by extraction procedure and ICP-MS* Element Found Certified Fe 56 96 As 2.5 1.6 Sb 7.5 8.0 Pb 7.6 3.2.5 Bi 0.65 0.5 Ag 13 12.2 * All values in pg g-'. anticipated that the incorporation of further internal standard to cover the lighter mass range may result in better agreement for Ag, As and Fe; however, this was not pursued. Solvent extraction is commonly used in sample preparation and was evaluated for the removal of copper from the metals of interest using a commercially available extractant, 2-hydroxy- 5-nonylbenzaldoxime, developed in the Mining Chemicals Research Group at ICI Specialties Research Centre and used for the extraction of copper in hydrometallurgical processes. Recovery experiments were carried out and for all elements recoveries of >95% were achieved. The extraction procedure was used to determine the elements of interest in SRMs 394 and 395 and the results are presented in Table 3. Good agreement was obtained between the results using the solvent extraction procedure and the certificate values for all elements excluding Fe and Pb. Following some initial analysis of real samples, the extrac- tion procedure was used to determine Sb only in a number of samples. The examples described trace metals analysis Conclusion represent some typical applications of carried out within ICI Specialties Research Centre. It is envisaged that trace metal analysis will become increasingly important, particularly for environmen- tally sensitive metals. References 1 ASTM B115-91 (02.01). American Society for Testing and Materials, Philadelphia, PA. 2 Rigby, I. A., and Stephen, S. C., presented at the Third International Conference on Plasma Source Mass Sepctrometry , University of Durham, 1992.

ISSN:0144-557X    

DOI:10.1039/AP9933000426

出版商:RSC    

年代:1993

数据来源: RSC

摘要:

ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 441 Analysis of Pentachlorophenol Using Extraction Methods, Derivatization and Gas Chromatography-Mass Spectrometry E. Helen Jenkins and Peter J. Baugh Department of Chemistry and Applied Chemistry, University of Salford, Salford M5 4WT Derivatization of pentachlorophenol (PCP) is recommended for reliable and quantitative detection at low levels in order to overcome the inherent chromatographic difficulties and analy- tical problems on a used (active) capillary column. On a deactivated or new column €or which the gas chromatographic (GC) peak shape is acceptable, PCP can be determined to picogram levels using gas chromatography-mass spectrometry (GC-MS) in the selected ion recording (SIR) mode but because of the active hydrogen PCP can be easily lost through adsorption on the chromatographic system. A variety of derivatizing agents have been used to form acetate (CH,CO), methyl (CH3), trimethylsilyl (TMS) and pentafluorobenzyl (PFB) derivatives of PCP. To date, although the incorporation of the t-butyldimethylsilyl (TBDMS) group has been widely employed in biological target analysis, giving rise to an enhanced M-57 ion in mass spectrometry, the use of this derivative has not been reported for PCP.This paper reports on the use of a TBDMS derivative for the analysis of PCP in a range of matrices arising from rivers: water, sediment/soil, sludge and commercial sources. Con- sideration is given also to extraction methods.442 ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 Derivatization For the purpose of determining the appropriate reagent, conditions for derivatization and solvent systems for the conversion and extractiodwork-up, a selected range of re- agents/solvents were employed.The GC-MS response for the acetate and silylether derivatives using reagents (CH3C0)20, bis( trimeth ylsil yl) trifluoroace tamide (BSTFA) , N-me th yl- tert-butyldime th ylsilyltrifluoroace tamide (MTBSTFA), TBDMSCl and trifluorosulfonate was observed. The TBDMS derivative obtained using MTBSTFA as the reagent exhibited the greatest response for (M-57)+ at m/z 321 (TBDMS>TMS>CH3CO). The most appropriate solvent for derivatization was acetonitrile which could also be used for the preparation of stockjstandard solutions and for spiking (water, other matrices) but not extraction via liquid-liquid extraction (LLE) or stream distillation extraction (SDE).Derivatization via MTBSTFA was found also to be possible in hexane, a good extraction solvent. Therefore, prior to derivatization, evaporation to the residue stage and then re-suspension in acetonitrile was required. 13C PCP was added at the derivatization stage to monitor the efficiency of the reaction but not as a surrogate at the initial stage (natural or spiked samples) to compensate for a loss in recovery. Duplicate derivatization on divided extracts was carried out to determine the reproducibility. Determination of the amount of PCP recovered was carried out by comparing the response of m/z 321 to that of mlz 329 for the 13C analogue. The GC-MS facility used was a Fisons instruments VG TRIO 1000 operating in the electron impact (EI) mode with a mass scan rate of 45450 u in 0.9 s.Gas chromatography was performed on a 14 m DB5,0.32 mm i.d., 0.25 pm df capillary column with the following conditions: initial temperaturehime, 80°C per 2 min; ramp rate, 20°C min-'; final temperature/time, 300 "C per 5 min. Extraction Comparative extraction was investigated using LLE and SDE. For LLE using hexane, toluene and dichloromethane as solvents, duplicate spiking was carried out with each extract after concentration to 1 ml being derivatized four times (0.1 ml portions). Percentage recoveries (YO R ) were 64.1, 66.6 and 73.3, respectively, for the three solvents studied with toluene showing the lowest relative standard deviation (RSD).Acid- base clean-up (double extraction at pH 12 then pH 1) showed loss of PCP, particularly severely for toluene. Steam distillation extraction was optimized for water and soil. For water the optimum % R , 90.7 and 91.6, was found for an SDE time of 4 h. An environmental quality standard (EQS) test was carried out using a spike of 0.5 ml of 400 ppb PCP in acetonitrile, 1000 ml of water (equivalent to a PCP level of 0.2 pg I-') at pH 1, 25 ml of hexane as extractant solvent and an SDE time of 4 h. The YoR obtained was 105.3 k 9.9. For sediment the optimum %R of 100.4 was obtained at a time of 16 h. Trace analysis optimization was carried out using 50g of sediment spiked with 0.5 ml of 20ppb PCP in acetonitrile (equivalent to a PCP level of 0.2 pg kg-') in 500 ml of water adjusted to pH 1 with 10 ml of concentrated acid, 25 ml of hexane as extractant solvent and an SDE time of 16 h.The YoR obtained was 101.6 k 2.2. It is clear that SDE with derivatization is capable of detection levels well below that required for an EQS for water. There is no EQS available for soil/sediment, although detec- tion limits for US Environmental Protection Agency contract work are listed. Here, likewise SDE with derivatization is capable of good recoveries L+ levels below those listed or required for water (EEC directives) using only GC-EI-MS in full scan mode. The use of SIR for characteristic ions would facilitate detection levels far beyond those currently required to be achieved. Conclusions To obtain reliable data for phenols such as PCP, derivatization is advised and TDBMS via MTBSTFA provides a system giving satisfactory results (particularly if the GC capillary column has become active).With SDE, an intermediate method of extraction relative to Soxhlet extraction, it can be demonstrated that high percent- age recoveries are obtainable with low RSD. For awkward matrices, i.e., discharge liquors, soils, sediment, solid waste and sludge, the extraction technique avoids the use of clean-up which may lead to losses prior to derivatization. The authors are grateful to the Science and Engineering Research Council for a studentship on appeal to one of us (E. H. J.). Preconcentration Methods for Determination of Copper, Cadmium, Lead and Zinc in Surface Waters: A Comparative Study Frederick Vernon and Cosmas D.Wani Department of Chemistry and Applied Chemistry, University of Salford, Salford, Lancashire Determination of trace metals at low concentrations is an important subject both for environmentalists and for health workers. Accurate and precise information is needed on concentrations of all metal impurities in water intended for drinking, therefore requiring sensitive and accurate methods for their determination. Many countries already have water quality standards and legislation stipulatin maximum accept- able concentrations for specific impurities!-3 Whereas, in technologically advanced countries, trace metal determinations will almost certainly rely on the use of electrothermal atomic absorption spectrometric (ETAAS) measurements of toxic species such as cadmium and lead in the pg 1-' (ppb) range of contamination, in third world countries conventional flame AAS may well be all that is available.This will necessitate the use of chemical preconcentration tech- niques to bring the metal concentration up to a level at which the instrument can determine it. Such preconcentration techniques include sample evap- oration, coprecipitation, solvent extraction and ion exchange, with the last two techniques predominating in the field of water analysis. Each technique has its adherents and remarkable claims (both for and against) are to be found in the published literature. This paper describes the results of preconcentration studies by evaporation, solvent extraction and cation exchange on solutions containing four metal species.Cadmium and lead were chosen as members of the group defined by the World Health Organization (WHO) as very toxic.4 Copper was chosen as a toxic but essential element, as to a lesser extent in terms of toxicity is zinc. Rigorous studies of percentageANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 443 recoveries of the four elements by each of the three precon- centration techniques were carried out on standard solutions. Five interconnected rivers in the north-west of England were sampled and their levels of cadmium, copper, lead and zinc were determined. Experimental Evaporation Metal stock solutions or filtered river water samples were acidified, with 0.5 cm’ of concentrated nitric acid being added to a 500 cm3 sample. The samples were evaporated to 5-10 cm3 (but not allowed to dry by hot-plate.To the concentrate was added a further 0.5 cm of nitric acid, the volume adjusted to 10-15 cm3 and any crystals allowed to dissolve. The final volume was adjusted to 25 cm3, giving a 20-fold concentration step for measurement by flame AAS. 4 Solvent Extraction Several chelating ligands were investigated for their extraction efficiencies of the four metals. These included 8-hydroxyquino- line, dithizone and ammonium pyrrolidin-1-yldithioformate [ammonium pyrrolidine dithiocarbamate (APDC)] of which APDC proved to be the most effective. Samples (500cm3) were adjusted to pH 7.5, APDC solution added and extracted with chloroform twice. The chloroform was evaporated and the residue digested by heating with concentrated nitric acid.After repeated diges- tions gave a clear solution, this was diluted to 25 cm3 giving a 20-fold concentration. Ion Exchange Ion exchange was carried out on Dowex 50 strong cation- exchange resin, 50-100 mesh size, used in the ammonium form. Conditions were as follows: column length, 15 cm; i.d., 1.4 cm; flow rate, 2.5-3 cm3 min-’. Samples of water (500 cm’), adjusted to pH 5.2, were passed through the column. The sorbed metals were eluted using 25 cm3 of 2 mol dmW3 nitric acid, giving a 20-fold concentration. Results Evaporation Fansworth’ reported good recoveries of trace elements after 20-fold concentration of standard solutions by evaporation as did Mislan and Elchuk6 with 70- and 250-fold preconcen- trations. However, more recently, the validity of the evap- oration technique has been questioned by Zolotov and Kuzmin’ where, in a most detailed study on many metals, they reported 5@-70%0 losses for copper, lead and zinc after evaporation.These incredibly high values support, to some extent, the work carried out by Yudelevitch and Shelpakova8 who stated that losses of cadmium, zinc and lead ‘became significant’ when using evaporation temperatures above 80 “C and reached 10-15% loss on boiling. In the work reported here, acidified water samples were evaporated by gentle boiling on a hot-plate. The recoveries on 1 or 10 ppb standard metal solutions are shown in Table 1, where each percentage recovery is the mean of 18 determi- nations. It can be seen that, unlike the earlier reported values, cadmium and zinc recoveries are highly efficient and, whilst the recoveries of copper and lead are less efficient, recoveries in excess of 90% are obtained for these two metals. Solvent Extraction Of the commonly employed ligands, it was found that APDC gave the highest extraction efficiencies.Several workers9-’ * have claimed that APDC, when used with hexan-2-one, gives an excellent extraction system. However, possibly due to the comparatively high solubility of this solvent in aqueous samples,12 we obtained variable recoveries which were also low, being under 80% for all four metals. As a consequence, the solvent chosen for the work was chloroform. Back- extraction of metal into nitric acid was investigated together with evaporation of the chloroform and nitric acid digestion of the metal complexes.The results are given in Table 2 and it can be seen that there are negligible differences between results for back-extraction into 6 mol dm-3 nitric acid and the solvent evaporatiodnitric acid digestion technique which was employed in subsequent work. With the exception of zinc (goo/, recovery), it can be seen that the other metal recoveries are above %YO, in complete agreement with Armannson13 who reported recoveries of 95% or above. Ion Exchange The highest recoveries from standard solutions were obtained by ion exchange. As can be seen from Table 3, recoveries of the four metals from standard solutions may be taken as quantitative above certain initial levels. With the exception of Table 1 Percentage recoveries of cadmium, copper, lead and zinc from standard solutions after 20-fold preconcentration by evaporation of acidified sample Recovery Standard Element ( Y O ) * deviation (YO) (a) Each metal examined separately - Cd 97 4.2 c u 93 8.9 Pb 90 7.8 Zn 98 2.3 Cd 96 4.0 c u 92 9.0 Pb 91 8.1 Zn 99 2.0 ( b ) Metals in admixture - * Percentage recovery is mean of 18 determinations.Table 2 Percentage recoveries of cadmium, copper, lead and zinc after preconcentration by solvent extraction using APDCkhloroform Recovery (%)* Element Back-extraction Acid digestion Cd 96 (1.2) 95 (1.5) c u 96 (0.4) 98 (0.4) Zn 90 (1 .O) 92 (1.7) Pb 95 (1.3) 95 (1.1) * Means of 18 determinations. Figures in parentheses are standard deviations. Table 3 Percentage recoveries of cadmium, copper, lead and zinc (at various initial concentrations) by ion exchange on Dowex 50 strong cation exchanger Initial con- Recovery Standard Element centration (ppb) (Yo 1 deviation Cd 5 94 3.7 10 97 1.8 20 100 0 c u 5 99 2.2 10 101 0.6 20 100 0 Pb 20 30 40 93 98 99 3.6 2.8 1.8 Zn 5 99 2.2 10 100 0 20 100 0.3444 ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 Prestwich \ Leigh 7Iford- Stretford 1 Altrincham Wilmslow Oldham Failsworth Y I Whaley Bridge Cheshire Fig.1 Interconnecting river system around the Greater Manchester area sampled for the study Table 4 Comparison of metal contents obtained for river waters by three preconcentration techniques and direct analysis by ETAAS Evaporation Solvent extraction Ion exchange ETAAS River Cd Cu Pb Zn Cd Cu Pb Zn Cd Cu Pb Zn Cd Cu Pb Zn Etherow 1.6 15 13 52 1.4 11 12 51 1.5 10 11 37 1.8 20 7 37 Goyt 2.0 23 14 55 1.8 21 11 50 1.9 20 12 48 1.8 25 6 29 Tame 2.8 22 25 105 2.3 18 22 99 2.5 16 22 96 2.3 25 12 33 Mersey 2.5 16 22 60 2.1 14 20 56 2.1 13 19 48 2.0 29 9 31 Irwell 3.4 20 25 65 2.6 18 18 59 2.8 17 20 54 2.8 41 10 33 these minimal concentrations, recoveries for cadmium , copper and zinc at initially 10 ppb levels, and of lead at 30 ppb levels, are all >97%. These findings are in total a reement with Florence and BatleyI4 and with Kingston et al.Trace Metal Contents of Rivers Samples of an interconnecting river system in north-west England (see Fig. 1) were taken; after acidification and filtration the samples were divided into four. Cadmium, copper, lead and zinc contents of each were determined by each of the three methods described here and the fourth sample of each river water was kept for direct analysis by ETAAS.Unfortunately, the direct analyses were carried out after the samples had been stored for several months and a lack of stability to extended storage must explain the spurious results obtained by ETAAS. Table 4 gives comparative results for the four metals as determined following each preconcentration method and by direct analysis. The ETAAS results prove that the keeping properties of the sample with respect to cadmium are very good but a comparison of direct analysis with preconcentration results demonstrates somewhat elevated values for copper contents whilst the lead and zinc results are approximately half of the values obtained by preconcentration.In general, very good agreement between the solvent extraction and the ion exchange results on a river is noted, with the evaporation result being slightly higher. a It is interesting to note that these rivers of the industrial north-west region, though usually regarded as having a considerable degree of pollution, actually comply with the maximum acceptable levels for the four metals given in the Guideline for Drinking Water Quality3 of WHO. In a further study of the rivers, where samples were taken at monthly intervals over a 6 month period, the minimum and maximum concentrations of each metal over the study period can be seen in Table 5. The same trends are obvious, with very good agreement between solvent extraction and ion exchange and slightly higher values obtained by evaporation.The trace levels in the rivers are remarkably consistent , no seasonal variation is apparent and the pollution of the river Tame by zinc for instance was a constant factor throughout the investigation period. In conclusion, solvent extraction would appear to be a perfectly satisfactory preconcentration method for the four metals as would ion exchange with the proviso that ion exchange efficiency appears to fall off at very high dilutions. This, however, only applies to cation exchange; chelating ion exchangers have not been shown to suffer from this defect. Evaporation, the simplest method of preconcentration, has been shown to be very efficient, certainly on a par with the other techniques studied, and provided that simple precautions are taken, i.e., slow evaporation rates and the use of acid- washed anti-bumping granules for instance, there is no valid reason why evaporation should not be used for the preconcen-ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 445 Table 5 Minimum and maximum contents (ppb) of the four metals in the rivers sampled monthly over a period of 6 months Evaporation Solvent extraction Ion exchange River Cd c u Pb Zn Cd Cu Pb Zn Cd c u Pb Zn Etherow 1.911.2 17/13 1519 59/45 131.2 1716 14/10 61/37 1.611.3 1219 1219 48/37 Goyt 2.511.6 31/12 15/11 58/53 1.811.5 26/16 14/10 56/43 2.311.6 23/16 14/11 47/37 Tame 3.112.5 32/11 34/19 110199 2.811.5 25/13 26/19 114183 3.012.3 19/14 24/18 120178 Mersey 2.812.2 17/14 28/17 68/53 2.511.8 16/12 24/15 60150 2.312.0 16/11 22/16 62/43 Irwell 4.712.2 30115 32/19 79/59 3.112.1 23/16 28/19 66/44 3.012.3 19/15 24/16 62/48 tration of surface waters in conjunction with conventional flame AAS.Whether or not a further order of magnitude in sensitivity may be realized by combining evaporation with ETAAS is a question still requiring investigation. References 1 World Health Organization, European Standards for Drinking Water Quality, WHO, Geneva, 1970. 2 World Health Organization, International Standards for Drink- ing Water Quality, 3rd edn., WHO Geneva, 1971. 3 World Health Organization, Guidelines for Drinking Water Quality, WHO, Geneva, 1984. 4 World Health Organization, Technical Report No. 532, Trace Elements in Human Nutrition, WHO, Geneva, 1973. 5 Fansworth, C. G., Analysis of Trace Elements in Natural Waters by AAS, Water and Sewage Works, 1972, p.52. 6 7 8 9 10 11 12 13 14 15 Mislan, J. P., and Elchuk, S., At. Absorpt. Newsl., 1968,7,71. Zolotov, Yu. A., and Kuzmin, N. M., in Wilson and Wilson’s Comprehensive Analytical Chemistry, ed. Svehla, G., Elsevier, New York, 1990. Yudelevitch, I . , and Shelpakova, J . , presented at the 6th International Symposium on High Purity Matter, Dresden, May 1985. Allan, J. E., Spectrochim. Acta, 1961, 17, 467. Willis, J. B., Anal. Chem., 1962, 34, 614. Brook, R. R., Presley, B. J., and Kaplan, J. R., Anal. Chim. Acta, 1967, 38, 321. Sturgeon, R. E., Berman, S. S., Desaulnier, A., and Russell, D. S., Talanta, 1980, 27, 85. Armannson, H., Anal. Chim. Acta, 1977, 88, 89. Florence, T. M., and Batley, G.F., Talanta, 1976, 23, 179. Kingston, H. M., Bernes, I. L., Brady, T. J., and Rains, T. C., Anal. Chem., 1978, 50, 2064. Trace Elements in Natural Zeolites Alan Dyer and lsaaq Zaafarany Cockcrot? Building, Department of Chemistry and Applied Chemistry, University of Salford, Salford M5 4WT Gordon R. Gilmore Universities Research Reactor, Ride y, Warrington, Cheshire Zeolites are hydrated aluminosilicate minerals, usually with easily accessible high ion-exchange capacities and water contents. Large deposits of zeolites of sedimentary origin exist at many locations on the earth’s surface and they are mined commercially in the USA, Indonesia, Japan, Cuba, Czechoslo- vakia, Italy and in other countries. The zeolite content of the mined rock can be high (> 900/), as in many USA deposits, or relatively low ( 4 0 % ) as in some zeolitized tuffs (e.g., in Hungary or Italy).These minerals have attracted considerable interest as a mineral resource, for waste water treatment (as near Lake Tahoe in Nevada or at Vaz near Budapest), for processing aqueous nuclear waste streams [in the SIXEP process at British Nuclear Fuels (BNF) plc, Sellafield and for use as animal feed supplements and soil amendment.’ The most popular zeolite for these uses is clinoptilolite, which is widely available in a high degree of purity. This paper examines the trace element Table 1 Details of clinoptilolite samples Sample no. Supplier Origin 1 Anaconda Copper (1010A) Death Valley, CA, USA 2 Phelps-Dodge Mudhills, CA, USA 3 D. Bish Los Alamos Sheaville, OR, USA 4 D.Bish Los Alamos Buckhorn, NM, USA 5 D. Bish Los Alamos Castle Creek, ID, USA 6 Pratley Corp, Kenmare Zululand, Natal, South (South Africa) Africa Table 2 Thermal neutron activation analyses for scandium determination Granite standard Coal standards Sample no. Zeolite ppm RSD* (%) ppm RSD* (%) 1 lOlOA 2.98 2.31 2.52 0.69 2 140 1.63 2.37 1.37 0.93 3 25525 3.53 2.35 2.96 0.86 4 27073 4.68 2.28 3.94 0.57 5 27083 2.58 2.33 2.17 0.77 6 Pratley 2.05 2.35 1.74 0.84 * RSD = relative standard deviation. concentration of six clinoptilolites ‘as received’ with a view to providing information on elements present and their mobili- ties. The known impurities are feldspars, quartz, calcite, clays and other zeolites (e.g., mordenite) but in the samples investigated no individual impurity is present in concentrations larger than 2% (calcite, quartz, clays).Experimental Epithermal and thermal neutron activation analyses were carried out at the Universities Research Reactor, Risley. Two standards were used, a granite (SARM 1 NIM-G) and a coal (SARM 20 SASOL BURG), both supplied by the Bureau of Analysed Standards, South Africa. The clinoptilolite samples are listed in Table 1.446 ANALYTICAL PROCEEDINGS, NOVEMBER 1993, VOL 30 2500 2000 I Ep n c 1500 - .- c I c g 1000 0" 500 0 1 2 3 4 5 6 Zeolite sample No. Fig. 1 Trace concentrations of Ba (I) and Ce (El) in clinoptilolites 80 1 60 A Ep .: 40 n C - I c 0, C 0 20 1 2 3 4 5 6 Zeolite sample No. Fig. 2 Trace concentrations of La (H), Th (a), Sm (0) and Hf (El) in clinoptilolites Experiments were carried out whereby analyses also were made on leachants comprising Na, K, Ca and NH4 chloride solutions for comparison with water leachants.All results were subjected to cluster analysis.2 Results Epithermal analyses showed no significant differences from thermal neutron irradiation results so will not be considered here. The concentrations were well correlated when interstan- dard comparisons were drawn. An example is seen in Table 2 for scandium determinations. The elements Ba and Ce were present in the highest trace concentrations (Fig. 1) whilst La, Th, Sm and Hf (Fig. 2) were in an intermediate range with U, Ta, Sc, Lu and Eu (Figs. 3 and 4) present at the lowest concentrations capable of reliable analysis. Water leaching 6 1 0 1 i 4 &1 5 2 3 Zeolite sample No. Fig. 3 Trace concentrations of U (H), Ta (U) clinoptilolites 2 1.5 A E Q - C 0 - 1 .- I 8 s CI 0.5 0 6 and Sc (El) in 1 2 3 4 5 6 Zeolite sample No. Fig. 4 Trace concentrations of Lu (H) and Eu (a) in clinoptilolites displaced Yb, Ce, Hf, Sc, Fe, La, As, Eu, Ta, Tb and Nd, whereas salt solutions additionally removed Mo, Cs, Rb, Mn, Sr, Ba. These results may point to the conclusion that the latter elements were from ion-exchange processes involving release of these species from cation-exchange sites in the zeolite, whereas the former elements arise from non-zeolitic impuri- ties. However, this conclusion may need some qualification by further experiments as zeolites may have some slight solubility in water. L. Cunliffe is thanked for producing Figs. 1-4. References 1 Dyer, A., Chem. Ind., 1984, 7, 241. 2 Clustan 1B User Manual, University of Manchester Regional Computer Centre, 1977.

ISSN:0144-557X    

DOI:10.1039/AP9933000441

出版商:RSC    

年代:1993

数据来源: RSC