ISSN:0144-557X    

DOI:10.1039/AP98825FX037

出版商:RSC    

年代:1988

数据来源: RSC

摘要:

ANPRDI 25(10) 317-340 (1988) Analytical Proceedings Proceedings of the Analytical Division of The Royal Society of Chemistry CONTENTS 'The Future Role of Analytical Chemistry in the Chemical Industry' by J. R. P. Clarke 'A Celebration of Twenty-one Years of the Automatic Methods Group' by D. Betteridge 'AMBIS-a Novel System for Microbiological Identification' by Soad Tabaqchali 'Role of Rapid Microbiological Techniques in the Food Industry' by M. R. Adams 'Chemical Analysis at Solid Surfaces' by J. N. Ness and D. J. Joyner 'Databases for Analytical Chemists' by G. F. Phillips 31 7 Research and Development Topics Meeting 318 SUMMARIES OF PAPERS 318 Analytical Chemistry-a Time for Change 318 323 21 Years in Automation 323 324 Automated Microbiological Analysis 324 325 328 Alternative Methods for Trace Elements 328 332 Databases for Analytical Chemists 332 334 Equipment News 336 Publications Received 33.8 Conferences and Meetings 338 Course 339 Analytical Division Diary , Typeset and printed by Black Bear Press Limited, Cambridge, England October 1988

ISSN:0144-557X    

DOI:10.1039/AP98825BX039

出版商:RSC    

年代:1988

数据来源: RSC

摘要:

ANALYTICAL PROCEEDINGS. OCTOBER 1988. VOL 35 317 Research and Development Topics Meeting The 1988 version of this popular meeting took place on July 18th and 19th, in Plymouth Polytechnic. This was the first occasion on which the meeting had been held in a Polytechnic, although it has previously been held in a College of Advanced Technology. Proceedings for 17 years, for much of that time as Editor. The President of the Division, Mr. D. C. M. Squirrell, presen- ted Mr. Weston with a glass paperweight in recognition of his service to the Analyt- ical Division. In accepting the gift Mr. Weston thanked his colleagues for their Queen’s University, Belfast. Earlier in the day two other presenta- tions had taken place, both connected with lectures. The fifteenth SAC Silver Medal was presented by Mr.Squirrell to Professor D. Littlejohn of the University of Strathclyde, and the fifth Ronald Mr. P. C. Weston (L) receiving a gift from Mr. D. C. M . Squirrell, President of the Analytical Division of the RSC Professor D. Littlejohn accepts the fifteenth SAC Silver Medal from the President On the Monday evening an informal assistance in maintaining the standard of Belcher Memorial Lecture scroll was both journals. Also at this time the formal presented to Dr. J. M. Slater of Birkbeck handover of the Presidential Badge of College, University of London. Office took place, the new President being Professor D. Thorburn Burns of the dinner was held, after which a presenta- tion was made to Mr. Philip C. Weston, who was shortly to leave the RSC having worked on the The Analyst and Analytical Dr. J . M . Slater receives the fifth Ronald Belcher Memorial Lecture scroll from the President Mr. Squirrell hands over the Presidential badge of office to Professor LI, Thorburn Burns

ISSN:0144-557X    

DOI:10.1039/AP9882500317

出版商:RSC    

年代:1988

数据来源: RSC

摘要:

318 ANALYTICAL PROCEEDINGS, OCTOBER 1988, VOL 25 Analytical Chemistry-a Time for Change The following is a summary of one of the papers presented at a Meeting of the Automatic Methods Group held on October 28-30th, 1987, in The Dormy Hotel, Ferndown, Dorset. The Future Role of Analytical Chemistry in the Chemical Industry J. R. P. Clarke Control and Electrical Group, Winnington Laboratories, Imperial Chemical Industries pic, P. 0. Box 7, Winnington, Northwich, Cheshire CW8 4DJ The concepts of the need to stay alive and of undertaking profitable activity are so basic that one may deduce many of the requirements of systems ranging from the simplest living cell to the most complex industry or learned society. The Requirements of the Chemical Industry The process industry, of which the chemical industry is but part, needs quantitative measurements: (1) to remain in business, by operating in a legal and socially acceptable way; and (2) in order to make profits through the efficient use of assets.The requirement to remain in business cannot be divorced from the need for sales and profit, or for an efficient interdisciplinary organisation, but some benefits may accrue from initially making this assumption. The Need to Remain in Business An industry which did not remain in business would soon cause wide-scale distress to its workers and their dependents, to equipment and service vendors, to direct customers and to its shareholders. However, western society places great emphasis on an individual person’s requirements, shown in decreasing order of importance in Table 1.As the highest duty of the State is to protect its citizens, any industry ignoring these rights could quickly have serious problems with the legislative mechanisms. In order to avoid the possibility of foreclosure, industry must continue to consider safety and hygiene factors and control the emission of gaseous and liquid effluents to the environment. Table 1. Hierarchy of human requirements and chemical and process industrial interests Human needs Industrial interests 2. To drink Clean water 3. To eat Good food 4. To be warm 5. To be healthy 6. To be protected 7. To be educated Survival . . 1. To breathe Clean air Shelter, clothes Drugs, medical diagnosis Weapons and a great variety of other things Labour force Profit . . 8. To be employed Labour force The UK legislature’s reliance on “best practicable means”1 and for all employers and employees to ensure “.. . health, safety and welfare at work”2 implies that there is a continual tendency to tighten standards as technology and medical science become more sophisticated. A responsible approach to chemical processing will always rely on sound engineering and operation as the basic means of preventing noxious leakages. Careful monitoring of legitimate exits and of the surrounding area will continue to be required as an extra major feature of chemical plants. The analytical scientist must be part of the decision-making process consider- ing the following analytical strategies exemplified for toxic gases. Legitimate vent monitoring Although cross-duct striation of analyte fluid, solid debris and physical constraints, such as high temperature, may make it difficult to obtain representative measurements in enclosed ducts, this is easier than measuring for leakages which may occur anywhere across a plant site.It is fairly certain what species are going to be present, so in this instance an emphasis on transducer selectivity may not be too important. Plant area monitoring When industrial hygiene local to a plant is well maintained, the environment outside the boundary fence is also likely to be satisfactory. A logical policy is therefore to make measure- ments close to the plant and have appropriate communication and action “strategies.” Thus, sensors monitoring acutely toxic vapours have their value enhanced by linking them both to local audible and visible alarms and to a remote visual display unit giving a plan of the site, the position and condition of all sensors, together with wind speed and direction.The remote siting of sensors across a plant points to the major cost of signal and power cables. Unfortunately, the rationalisation of serial transmission by radio or hard wire links has hardly been over-enthusiastic thus far. Some expensive transducers have their area of coverage enhanced by piping samples to them, but this often leads to long delays and or loss of sensitivity. This “plumbing” technology is not well developed. The improvement of “sampling in a line” reaches a peak in freely steerable open-path laser systems, which are analogous to radar.Less ambitious and less expensive fixed reflector systems may be more attractive. Leak seeking Even if air movements are favourable, area monitors are unlikely to pin-point the precise position of an emission. This needs sensitive, rapidly responding, intrinsically safe, leak- seeking equipment to nose down to the source of the vapour plume. In the absence of a monitoring array, regular application of leak-seeking equipment allows management to nip minor emissions from likely places in the bud. Person a1 mon it0 rs The human nose has evolved to aid survival by monitoring food quality. Ideally sited as a sampling device, it can detect manyAKALYTICAL PROCEEDINGS, OCTOBER 1988, VOL 25 319 industrial toxic vapours. One might enhance the effectiveness of this “free” sensor by the wider addition of inert dopants to relatively odour free materials, as has been done by British Gas. The other senses of sight and hearing should never be completely ignored for gas monitoring, especially when used in combination with the nose and with built-in intelligence.Artificial monitoring systems, worn in the breathing zone, are in many ways ideal for hygiene monitoring m d are an important development area. Size and weight factors are critical to acceptability and proper usage. Successful designs will have built-in alarms. Personal monitors may also be used for plant survey work. Portable monitors Regrettably, at the present state of the art, it is not possible to provide wearable monitors for every situation. Nevertheless, portable equipment placed close to the worker can offer useful protection, for example, prior to entry of an enclosed space.Biological monitoring Healthy communities of plants, animals and microorganisms indicate good living conditions and provide evidence of satisfactory process operation. Hence, the principle of intro- ducing biological material to trap and sense fluid effluents for general or specific toxicity should not be discounted. Such a strategy might include physiological testing of the process staff. The Need to Make Profit The hierarchy of human needs in Table 1 shows that once survival is secured, a more sophisticated range of requirements are demanded. The western chemical industry is following this trend to satisfy its affluent customers. Chemists will realise that this implies more higher relative molecular mass solid pro- ducts.Our analysis problems will be compounded by the discontinuous batch-wise production of a great variety of materials. The control of crystal growth, precipitation, the size, shape or surface of powders, fibres or films will all be critical. Many transducers are needed to monitor efficient bioreplica- tion of products based on chemistries evolved over millions of years which touch on health and food. However, we must beware of extrapolating this viewpoint too far and not forget commodity chemicals, which will always provide a market for the efficient producer operating in an area of political stability from cheap feedstocks. Although there may need to be some prompting by analytical scientists, industry’s managers should be able to lay down measurement requirements based on the “market’s pull.” Research Councils and individual R&D staff throughout the UK have probably underestimated the value of such discussions to focus the mind and trigger the application of technology. It also could be argued that while analytical scientists must react to business needs, this is too late and by no means far sighted or especially collaborative. There should be inter- disciplinary problem solving at even earlier stages. For example, the development of medical diagnostic kits as a business venture is almost wholly dependent on analytical skills. The analytical scientist will often not need telling what to develop but will offer his “technology push” to solve a company’s problem on-plant or downstream in the market place.Detailed market and technical needs Table 2 shows some examples of general market needs in the area of chemical measurement technology. Gaseous effluent monitoring was discussed earlier and a lower hierarchy of some consequential technical needs is given in Table 3. Each need in Table 3 has to be further translated by the qualified analytical scientist into subordinate hierarchical layers of technical requirements, and so on. Table 2. Some general needs for analytical measurement To remain in business: i. Gaseous effluent monitoring ii. Liquid effluent monitoring To remain profitable: i. Analysis and control of laboratory-scale reactions ii. Rapid analysis of batch plant products 111. Reduced signal and power transmission costs iv.Improved precision of off-line analysis (e.g., by better sam- v. Automation of solid sample preparation vi. Enhanced confidence in instrumentation vii. More useful information at lower cost viii. Reduction of maintenance costs ix. Safe operation of unattended laboratory equipment x. Selection of effective sampling systems xi. Selection of optimum transducer systems xii. Application of laboratory equipment to on-plant use ... pling) Table 3. Some technical needs for gaseous effluent monitoring i. Better piped sampling for area monitors ii. Area monitor communication and action systems iii. “In a line” sensing (e.g., open-path IR) iv. Personal monitors (more sensitive and greater variety) v. Arrays of different sensors (to gain selectivity) vi.Microorganism-based effluent sensors Meeting the Requirements of the Chemical Industry Organisation The late 1980s have seen a considerable reduction in the chemical industry’s manpower. In these circumstances, unless companies are clever enough to realise greater potential from their existing staff, a technical competitive edge can be lost. Since the UK achieves only about 5% of the world’s R&D, any single organisation is doing very well if only 99.9% R&D is undertaken outside its direct control. It is imperative that self-sufficiency is exchanged for a “we gladly accept, barter or pay for any knowledge or help we can get” attitude. Any industrial project of magnitude is interdisciplinary so the outward look begins in one’s department by persuading staff to live by, not merely acquiesce to, the concept of gearing up their own efforts through personal contacts.Accountants who change their budgetary control to increase the necessary external cash flow will be repaid many times. Awareness It is essential that analytical scientists who can lead others are aware of what is happening outside their department, company and country. This is done through symposia, by reading the external literature, including manufacturer’s catalogues, and by maintaining disciplined internal verbal and written report- ing. Such staff will also develop the commercial tetrahedron of personal relationships between users who have need of equipment, researchers who have ideas to meet this need, without the means of putting them into commercial practice, vendors who develop, manufacture, sell and service systems and investors who catalyse these activities.Learned Societies perform an insufficiently recognised service by organising meetings where the necessary four-way awareness develops. Process Analysis When new plant is being designed, qualified analytical scientists are needed to understand present and future process320 ANALYTICAL PROCEEDINGS. OCTOBER 1988. VOL 95 requirements and on- and off-line analysis in order to assess the necessary measurements and how they will be made. They must also decide where measurements should be carried out on the plant or in a local or central laboratory, in order to create an effective operating strategy. Initial requests for analytical measurements are often changed if the reasons for them are probed.Such discussions cannot take place too soon. On-line analysis is frequently put in research-bench or pilot-scale reactors in order to develop a process and so determine the physical characteristics of the full-scale plant. Equally, many analyses are only needed during start-up or for fault diagnosis, but how many are continued unnecessarily? Process analysis strategy should be reviewed on a regular basis throughout the life of the plant in order to solve problems which may arise from new technical or commercial circum- stances and take advantage of significant analytical innovation. The Development of Analytical Technique Equipment vendors will be only too aware that process managers have little interest in technique but only in efficient measurement.This comprises the samp:,..g system, the trans- ducer and the signal handling equipment (Table 4). Few users, equipment vendors or even university research- ers are able to study analytical technique without some thought of its commercial potential. Nevertheless, commercial com- panies should beware of the current national trend of reducing the study or even awareness of this technology, so reducing the chance that appropriate techniques are triggered by the market’s needs. Sampling systems Sampling systems are almost universally acknowledged by users and vendors to be the area where problems arise most often. It is terrifying to contemplate the amount of careful, laboratory work carried out on inadequate samples derived by means of poor organisation or technique.Table 4. Components of analytical measurement systems (A) Sampling system Calibration Centrifugation Classification Comminution De-gassing De-misting Dilution Dispensing Dissolution Distillation Drying Extraction Filtering Flotation Flow control Metering Mixing Precipitation Pressure control Pumping Sedimentation Separation Siphoning Stream dividing Stream switching Stripping Sublimation Temperature control Transport Vaporising (B) Transduction systems based on Chemical reaction Electric fields Electromagnetic radiation Mechanical energy Magnetic fields Nuclear reactions Thermal energy (C) Signal- Alarm analysis and control Analyser control Analyser fault diagnosis Compensation for second-order effects, e.g., temperature handling system Data presentation Data processing Data storage Data transmission Linearisation Verification of results Perhaps I may strike a chord by saying “forget quality assurance schemes if sampling is done improperly.’’ A major bottleneck to full laboratory automation lies in the preparation of samples.The unit operations shown in Table 4(A), in this instance compatible with both the chemist and with a suitable robotic local transfer system, appear to be the way towards the key task of preparing homogeneous solutions of known concentration from given liquid or solid samples. Successful sampling systems have to meet several criteria. 1. Representation of the measurand. Good sampling takes material which is representative of what is to be measured. Every such molecule should have an equal opportunity of being analysed.This does not necessarily give a truly representative sample, since low volumes of rust, for example, might be analytically ignored. 2. Physical or chemical preparation of the sample. The sampling system should supply the transducer with material under the conditions of concentration range, temperature, pressure, flow and phase which can be accepted. Thus, pipe scale may have to be removed to protect the transducer. 3. Safety requirements. The need for safety in operation and during maintenance is important. For example, the use of robust, double isolation or isolation followed by bleed-off valves is common in process analysis. Detailed assessment of what can go wrong is a useful concept not only for safety, but also for the whole of process analysis system design.Automated laboratory equipment, like robot systems, which will increasingly be called upon to run unattended overnight, need to have their safety aspects considered carefully to allow for mechanical failure, wear and inaccuracy, breakages, leaks, floods and flammable and electrical hazards. 4. Transport of the sample. The sampling system should transport the sample, without changing its nature, in an appropriate time to the transducer and may also need to ensure its safe disposal or return. Control of temperature and pressure or the addition of a suitable fluid diluent may avoid the embarrassment of precipi- tation, condensation or further reaction. The loss of traces of polar materials in sample-line walls is a common problem which may be minimised by rapid flow-rates and suitable materials of construction.Multi-stream sampling enables more than one fluid stream to be fed in turn to a single transducer. Although it adds complication, it can be a useful means of saving the cost of several analysers. The UKAEA’s lead in power fluidic technology, which has been under-exploited for process analysis, contains many answers for sample transport. 5. Calibration and standardisation. There is a need either for standardised material to be added to the transducer or for a means of removing material, unchanged, for laboratory analysis. Perversely, the off-line checking of on-line analyses can lead to serious differences of opinion. While the laboratory manager trusts his analysts, it is most unwise for him to believe that manual methods are more precise than automated systems.Laboratory robots usually give two or three times greater precision than routine manual methods and on-line methods are generally about as good as an expert making a single check. These differences often occur for sampling reasons. The successful sampling system is often a combination of parts, each providing one or more specific operations. Every one of the sampling operations, shown in Table 4(A), is worthy of study in its own right. A useful R&D exercise is to think ofANALYTICAL PROCEEDINGS, OCTOBER 1988. VOL 3 -32 1 ten different ways to achieve each function in order to have a box of Meccano parts to meet the market’s need. However, there remains the problem of picking the right parts to match the process stream to the transducer! Transducer systems Table 4(B) makes no attempt to go into the details of possible chemical composition transducers.The number of basic types is probably over 100 and manufacturers’ models, each with their own advantages and disadvantages, run into thousands. The situation is more complex as the transducer is especially dependent on its sampling system, to say nothing of the associated signal-handling system. Few users take proper stock of the system options for new projects. Vendors particularly ought to be aware of the continual developments in transducer characteristics (Table 5 ) which may make a preferred system one year obsolete the next. Optimising the choice of transducers is an important develop- ment pioneered by the Warren Spring Laboratory. The system designer is usually under some constraint as to capital costs, but user companies would do well to pay more attention to running costs, which, averaging 20% installed capital p.a., are a considerable proportion of the life-cycle costs of the measure- ment system.Table 5 . Transducer characteristics Accuracy Ambient operating conditions, temperature. pressure, vibration. humidity Capital cost Corrosion resistance-internal and external Credibility Dynamic range Fault diagnosis Fouling resistance Installation cost Life Maintenance requirements Mechanical robustness Power and other service requirements Precision Reliability Running costs Sample conditions, e.g., temperature, pressure and phase Selectivity Size Speed of response Stability-long- and short-term Mass Universality analyser checks revealed any faults, but that most calls caused dislocation of production.In order to save maintenance costs and keep the operators’ confidence, much attention is now being paid to monitoring performance and diagnosing analyser faults. Key parameters such as voltage, flow and pressure must be correct for adequate operation and auto-checking systems are almost mandatory for new designs. In addition to auto-fault diagnosis, it is good psychology to allow the process operator to initiate check procedures. Hence, a manual check system greatly improved the market for an already very reliable electrochemical chlorine sensor .4 Although specific checks are valuable for specific trans- ducers, a great deal of work is needed to cover every class of analyser.A more general approach to validation is the assessment of the correct noise in the output signal coupled to a knowledge of local operating conditions. It is believed that there is considerable opportunity for university researchers to join with equipment vendors and users to produce standard packages to meet signal handling requirements. Conclusions The future of analytical chemistry lies not only in advances in technique but in changes of organisation and ways of working to solve industry’s problems. Consider important needs Analytical chemistry should be based on Industry’s require- ment to stay alive and be profitable. The consequential needs may be obvious or can be revealed through the on-going study of technique derived from discussion with business manage- ment.Check assumptions Many managers and researchers are pressing for new trans- ducers. However, the benefits of this work are only seen in real applications and it is the measurement system, not the transducer, which the market judges. Transfer skills It is easy, and not clever, for an organisation to fall into the self-sufficiency trap, but it costs money to avoid or climb out of it. As >99.9% R&D is not under an organisation’s control it is essential to be aware of, and apply, others’ existing skills and technologies. A significant improvement in maintenance and hence reduction in operating costs of on-line equipment has been through the development of analysis houses. Careful attention to ventilation and fail-safe systems allows toxic, asphyxiant or flammable samples to be handled with acceptably low risk.Such houses allow equipment based on laboratory designs to be effectively maintained close to the plant even when no other protection is available. Manufacturers and suppliers of on-line systems should recognise both the dangers and the opportunities for their present business arising from the automation of laboratory testing. Their expertise in sampling systems, installation and unattended operation could be applied to laboratory instrumentation. Signal-handling systems Modern electronics has allowed us to undertake the complex operations in Table 4(C) much more effectively than ever before.There are few practical limits which cannot in principle be achieved. In 1980 Shaw3 claimed that less than 20% of calls for on-line Think widely Initial thoughts are often not the best but can stimulate better ideas later. Solving a problem in several different ways can be very effective in getting a really good solution. Do not extrapolate too f a r Extrapolation is a form of arrogance that thinking widely or changing circumstances will probably show to be unjustified in the far future if not before. Be entrepreneurial It is necessary to act quickly where there is good opportunity to match needs with a skill or product. Progress should be reviewed regularly and the good entrepreneur knows when to transfer his attention to a more profitable course of action.It would be good to put more commercial aggression into UK chemical analysis by means of the tetrahedron of relation- ships. The Department of Trade and Industry is a willing advisor and investor. A major supplier doubled sales to ICI in 12 months after deciding to share development confidences.322 Many University and Polytechnic staff are very keen to put their knowledge to practical use. The right partners will inspire them with their needs, and give legal and commercial guidance. Analytical scientists must take the lead in their subject, generating a living relationship with other disciplines. They should make both day-to-day and big decisions, taking a strong lead to solve the problems of chemical processes. This will raise salaries and status and attract youth to their profession.Light Microscopy is one of the oldest techniques at the disposal of the analyst and is unfortunately greatly undervalued and underused in the analytical laboratory. It is, in fact, a conventional economical technique which should not be overlooked and can be of great value in the analysis of foods, pharmaceuticals, metals, plastics, water, agrochemicals, textiles and much more. In this book the authors draw upon their considerable experience in industry and consulting practice, to provide examples of the many and varied uses of light microscopy in analysis. They describe in detail its capabilities and seek to encourage its wider use in actual practice, reminding analysts of its qualities and applications. They also advocate good practice in its use. Microscopists, analysts and students alike will gain much from the authors’ enthusiasm and as a result may assist in extending the utility of the instrument into the future. ANALYTICAL PROCEEDINGS, OCTOBER 1988. VOL 25 References 1. 2. 3. Alkali and Works Regulation A c t , 1906. Health and Safety at Work, etc., Act, 1974. Shaw, R., “The Measurement and Instrumentation Needs of the UK in the Early 1980s,” IEE Colloquium. London, February 1980. Bamford, R. A . , Clarke, J . R. P., and Farr. T. F., Eur. Pat.. 0039549, 1980. 4. An Introduction to Applications of Light Microscopy in Analysis By D. Simpson and W.G. Simpson, Analysis far Industry, Thorpe-le-soken Due Summer I988 Price dE29.50 ($63.00) ISBN 0 85 186 987 4. Hardcover approx. 2OOpp Information W/ Services To order or for further information, please write to: Royal Society of Chemistry, Distribution Centre, Blackhorse Road, Letchworth, Herts SG6 IHN, UK. or telephone (0462) 672555 quoting your credit card details. We now accept Access/Visa/MasterCard/EuroCard. RSC Members are entitled to a discount on most RSC publications and should write to: Membership Manager, Royal Society of Chemistry, 30 Russell Square, London WClB SDT, UK.

ISSN:0144-557X    

DOI:10.1039/AP9882500318

出版商:RSC    

年代:1988

数据来源: RSC

摘要:

ANALYTICAL PROCEEDINGS, OCTOBER 1988. VOL 25 323 21 Years in Automation The following is a summary of the paper presented at a Meeting of the Automatic Methods Group held on January 28th, 1988, in the Whitbread Conference Centre, London. A Celebration of Twenty-one Years of the Automatic Methods Group D. Betteridge BP Research Centre, Sunbury-on-Thames, Middlesex Tw16 7LN Twenty-first birthday parties provide an opportunity to look back, be complimentary about the present and offer a hazy view of the future. We shall follow the custom, with reference to the key issues of: automated analysis, sampling, analytical measurement, data analysis, information usage and control. Control The control issue underlies all of the systems covered. In the slides shown, the change from mechanical automation to microchip via relays, valves and semiconductors was im- mediately evident.The changes in control algorithms, which are currently revolutionising the power of automated systems, were highlighted. Sampling The bugbear of analysis is sampling and sample preparation. For a long time it has been the major challenge of automated analysis. Progress has been made with automated sampling trays, but the real breakthrough has only been in the last 4 4 years with the arrival of reliable laboratory robots. In terms of laboratory practice, the ability to carry out dangerous and or tedious manipulations safely and continuously will transform the laboratory completely. Within the next 10 years our current style of flasks, beakers and reaction vessels will seem as outmoded as alchemical ware.Analytical Measurement Repeatable operations, digital data and control have led to improvements in throughput, accuracy, sensitivity and com- plexity in well known techniques such as spectroscopy and chromatography. Novel methods which derive from the possibilities of automation have been devised, such as continu- ous flow analysis (Technicon AutoAnalyzer), flow injection analysis and thin film methods of analysis. Slides of before and after automation demonstrated the dramatic improvements which have been brought about in analytical methods over the last 21 years. There is little sign of innovation abating. Data Analysis and Use of Information A major reason for improvements in automation is the enhanced capability of the storage and analysis of data.At the start of our period of review all results were recorded by hand in laboratory notebooks; in the early days of automation signals were output on recorder chart paper prior to measure- ment and transfer to notebooks. The microchip has certainly saved trees in Finland and shortened the time between measurement and report. It has also opened up the opportunity for the analytical system to be part of a much greater information and control system. The analyst should welcome this, as it offers the possibility of analytical measurements being incorporated directly into the decision-making processes of plant operations, site operations and sales. The Future As to the future, my crystal ball has light and dark parts. On the bright side is an extension of the developments noted above, the opportunities for analysts being important players in major developments.The goal must be fully integrated, automated analysis and information systems, and that should prove an exciting challenge to us. On the dark side are: (a) the efforts of professional societies to place bounds upon the activities of members (qualification committees) ; (b) the University ethos which separates pure and applied science and makes interdisciplinary activity very difficult; our urgent need is to get alongside the engineers and computer scientists who are building big systems with scant reference to the analyst; (c) the absence of a coherent academic discipline of automation, which ensures that only brave souls and/or idiots research or work on automated systems and which helps grant applications to fall through the cracks. If the Fairy Godmother granted one wish it would be for a textbook on automatic and automated analysis which would have the same revolutionary impact as say Cotton and Wilkinson, Cram and Hammond, Kolthoff and Sandell or Glasstone did in their day. The Automatic Methods Group has done a good job for 21 years; long may it continue.

ISSN:0144-557X    

DOI:10.1039/AP9882500323

出版商:RSC    

年代:1988

数据来源: RSC

摘要:

323 ANALYTICAL PROCEEDINGS, OCTOBER 1988. VOL 25 Automated Microbiological Analysis The following are summaries of two of the papers presented at a Joint Meeting of the Biological Methods and Automatic Methods Groups held on February 1 Ith, 1988, in the Robin Brook Centre, St. Bartholomew’s Hospital, London. AMBlS-a Novel System for Microbiological Identification Soad Tabaqchali Department of Medical Microbiolog y, St. Bartholomew‘s Hospital Medical College, West Smith field, London €CIA 7BE In general, microbiological identification of bacteria still relies on morphology and the results of a series of biochemical tests. The sub-division and typing of organisms are mainly dependent on serotyping or phage typing. These conventional methods are time consuming and cumbersome to perform.There is no single general method that can be applied to all organisms. In recent years, various new approaches to taxonomy have been introduced, and extensive efforts are being made to exploit new technologies and automation in clinical micro- biology. This paper presents a novel approach to the identification of bacteria. The method, which was developed at .St. Barthol- ornew’s Hospital, started with a chance contamination of an experiment and has now developed into a commercially viable system, the AMBIS system.1 The method is based on pattern matching of %-labelled proteins. It has the potential of identifying bacteria to species and subspecies level in a single run. A more detailed report of this method has been published elsewhere. 1 Method A 50-100-p1 volume of methionine-free medium (Eagle’s or Difco) containing 1 pl of [35S]methionine (about 10 pCi) is inoculated with a portion of 1-2 colonies of pure culture from a blood agar plate.The mixture is then incubated at 37°C for 0.5-2 h, aerobically or anaerobically, depending on the organism. At the end of the incubation, an equal volume of double strength buffer is added, the mixture boiled for 2 min, cooled to room temperature and subjected to electrophoresis on 12.5% polyacrylamide ge12; 10-18 samples can be applied to each gel. At the end of the run, the gels are fixed, dried and autoradiographed. Each bacterial species generates a specific radiolabelled protein pattern as visualised by autoradiography. Identification of Bacteria A range of different bacterial species, aerobic and anaerobic, Gram positive and Gram negative, cocci and bacilli, were tested.In each instance there were sufficient differences between the protein profiles to distinguish between the species and, at the same time, there were sufficient similarities in the pattern between related species to enable grouping of the genera. Typing of Bacteria Having established that the method was capable of differentiat- ing between bacterial species, it was important to determine if it could be of immediate practical application, i.e., whether it could differentiate within the species and provide new typing methods for the pathogenic organisms for which existing typing methods were unavailable or unsatisfactory. The method was first applied to various E.coli serotypes and each gave a different pattern, showing that there were sufficient detailed intra-species differences to perform sub-division or typing of these organisms. The method was then applied successfully to the typing of Clostridium difficile, the causative organism of pseudomembranous colitis, antibiotic-associated colitis and antibiotic-associated diarrhoea. Nine distinct types were iden- tified, A-E and W-Z, based on the position of the major protein bands.3 These major protein bands were shown to be strain specific and immunogenic.4 Restriction endonuclease analysis of the DNA from these nine strains showed individual patterns for each type,s confirming the reliability of this typing scheme. Epidemiological studies carried out using this typing scheme revealed that nosocomial acquisition and cross-infec- tion of C.difficile occurred among immunocompromised patients6 and that symptoms were related to type. The method was also applied to the typing of the methicillin- resistant Staphylococcus aureus (MRSA) , which was causing outbreaks in hospitals,’ and to the coagulase negative staphylo- cocci,S which have in recent years emerged as important opportunistic pathogens. None of the existing typing methods have proved adequate. [35S]Methionine-labelled protein pro- files were found to be particularly useful in studying the epidemiology of these organisms. This method has also been applied to the typing of Aeromonas species.9 Development of an Automated System (AMBIS) The above studies were carried out using autoradiography which, although highly sensitive, is slow, and it is difficult to distinguish between runs. The method should be rapid and automated in order to have wide applications. A scanner was needed to scan the dried gels directly, and a computer with pattern recognition software to analyse the data.Scanner A two-dimensional scanner for beta emission, which combined high resolution with high sensitivity and was capable of scanning the dried gels directly, was developed. The scanner head consisted of 12 well separated cathode strips at right- angles above 26 fine horizontal anode wires to give 312 discrete detection points. Each point moves to 150 positions on the gel, thus collecting data from 46800 sample sites. The scanner is connected and operated by an IBM PCIAT computer.The gel is placed on the sample platen and scanned for 0.25-1 h, depending on the acti?ity in the gel. Computer - VDU System An IBM PC/AT computer, with high-quality graphics screen , controls the system, which includes the scanner, the printer andANALYTICAL PROCEEDINGS. OCTOBER 1988. VOL 25 325 the electrophoresis unit, and also collects, stores and analyses the data. It has fast program execution and data-processing ability, permitting scanning of a gel and provision of analysis of data in 30-60 min. Automated Electrophoresis Unit To reduce inter-laboratory variations in electrophoresis, a flat-bed computer-controlled electrophoresis unit (AMBIS EP tower) was developed. Special sensors automatically terminate the end of the run.Pre-cast gels and buffers have also been developed. Retrieval and Analysis of ‘Data At the end of a scan. the data are retrieved on the VDU, where a picture resembling the autoradiograph is presented for analysis. Each lane is boxed-in separately and the data are extracted as a histogram representing the density and width of each of the protein bands for that particular bacterial strain. Relative molecular mass standards are included on each gel, and also a standard strain of bacteria (Serratia marcescens). The data are analysed using a number of different computer software systems. The facilities available are as follows: 1. Relative molecular mass calibration graph. The relative masses of selected peaks can be identified and calculated. This facility can provide useful information for certain bacterial species with simple protein patterns, such as C.difficife, to differentiate between the types. 2. Pattern recognition software. A program based on the Fourier transformation datalo compares different scans by transforming the channel data into a wavefunction and determining the sine and cosine components of that function. The Pearson product moment correlation coefficient” is also used as an alternative pattern matching algorithm. These algorithms can be used to match “unknowns” against a database to provide a potential identification system, or for cluster analysis to provide a classification system. 3. Rubberbanding. This is a facility that enables the investi- gator to zoom on to small areas of histograms showing maximum differences and expand these areas to occupy the full length of the channel (360 pixels).Comparison of these expanded areas will reveal sufficient differences to permit discrimination. This facility is particularly useful in comparing closely related bacterial species and in identifying intra-species differences to provide new typing schemes. 4. Normalisation. This facility provides compensation for small variations in protein separation which could occur owing to different gel batches, minor buffer changes and running conditions. Using the relative molecular mass standards as markers, the scans can be adjusted by 10 pixel positions to realign the scans and enable comparisons between the different gels. 5 . Cluster analysis. Cluster analysis, based on the unweigh- ted pair group method using averages (UPGMA)” and plotted as a dendrogram, has been introduced to provide a similarity matrix.This is particularly useful in expressing similarities and dissimilarities between organisms. Similar organisms can be grouped together. Cluster analysis has been applied success- fully to eight standard types of C. difficile. It is clear that several methods have to be adopted for the analysis of the data and the construction of database libraries. The available software has so far allowed comparisons between gels and correctly identified duplicate “unknowns” from other gels. This technique provides a general rapid and simple semi- automated method for the identification and typing of bacteria. Software is constantly being upgraded to meet new require- ments and challenges.It is predicted that this method will be more widely used in the near future. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. References Tabaqchali, S., Silman, R., and Holland, D., J. Clin. Pathol., 1987,40,1070. Laemmli, U. K., Nature (London), 1970,227,680. Tabaqchali, S . , O’Farrell, S., Holland. D., and Silman, R., Lancet, 1984, 1,935. Heard, S. R., Rasburn, B., Matthews, R. C., and Tabaqchali, S., J. Clin. Microbiol., 1986, 24, 384. Wren, B. W. , and Tabaqchali, S., J. Clin. Microbiol., 1987,25, 2402. Heard, S. R., O’Farrell, S., Holland, D., Crook, S., and Tabaqchali, S., J. Infect. Dk., 1986, 153, 159. Stephenson, J. R., Crook, S., andTabaqchali, S., Br. Med. J . , 1986,293,581. Stephenson, J. R., and Tabaqchali, S., J .Clin. Pathol., 1986, 39, 1271. Stephenson, J. R., Millership, S. E., and Tabaqchali, S.. J. Med. Microbiol., 1987, 24, 113. Sneath, P. H. A.. ”Identification of Microorganisms,” in Norris, J. R., and Richmond, M. H., Editors, “Essays in Microbiology,” Volume 10, Wiley, Chichester, 1978, pp. 1-32. Sneath, P. H. A., and Sokal, R. R., “Numerical Taxonomy: the Principles and Practice of Numerical Classification,” Freeman, San Francisco, 1973. Role of Rapid Microbiological Techniques in the Food Industry M. R. Adams Department of Microbiology, University of Surrey, Guildford, Surrey, GU2 5XH The importance that industry attaches to microbiological hazards associated with foods was reflected in the results of a survey conducted in the USA more than 10 years ago (Table 1).Table 1. Relative priorities given to food hazards' Food Actual industry Press Microbiological . . 1 1 5 Nutritional . . . . 2 2 4 Environmental contaminants . . 3 5 2 Natural toxicants . . 4 6 6 Pesticideresidues . . 5 4 1 Foodadditives . . 6 3 3 Fringe groups 5 4 3 6 2 1 FDA 3 5 4 6 2 1 While the priorities of public opinion, the press and other groups have undoubtedly changed since then (nutrition would, I suspect, receive far greater prominence now), microbial hazards remain pre-eminent in the mind of the industrialist. Recent examples have demonstrated the catastrophic conse- quences for a company if one of its products is associated with a food poisoning outbreak. Less dramatically, failure to control the usual spoilage microflora of a food and keep it to the minimum practicable level will produce chronic economic losses as a result of a reduced product shelf-life and variability of quality.Attempting to control these hazards through the acceptance or rejection of batches of final product on the basis of microbiological criteria is ineffective and wasteful compared with controlling microbiological qualitv at source during326 ANALYTICAL PROCEEDINGS. OCTOBER 1988. VOL 25 processing. The hazard analysis critical control point (HACCP) concept is one approach to this that is currently much in vogue. Essentially it represents the systematic application of our knowledge of the microbial ecology of foods to particular processes. 1. A detailed analysis of a food production process in order to identify the hazards associated with that particular process.2. As a result of this survey, critical points in the process can be identified, which, if not rigorously controlled, could lead to contamination with food-borne pathogens or spoilage microorganisms, their survival or unacceptable growth. These control points can sometimes be very closely defined, such as temperature and time conditions relating to a pasteurisation process, or can be more general, such as the necessity for good hygienic practices in a particular opera- tion, e.g., dressing a carcass. 3. The final stage is then to devise tests to monitor critical points and ensure that control is maintained. Once again some of these are hard objective measurements such as temperature and time recording, pH, moisture content or enzyme inactivation, or they can be more subjective such as close supervision and inspection to ensure hygienic prac- tices are maintained.Although physical or chemical tests are widely used at critical control points, this does not eliminate the need for microbiological testing of final product, product in process and the processing environment. The analytical problems that this poses arise from the generally low concentrations of micro- organisms present (a population of l o 5 bacteria per gram would correspond to a concentration of 0.1-1.0 p.p.m.) and the fact that they are non-uniformly dispersed in a food matrix of largely similar chemical composition, i. e. , proteins, nucleic acids, etc. The traditional solution to these problems is to subject multiple samples to counting procedures that employ the useful self-amplifying property of viable microorganisms.On a solid nutritive medium under appropriate conditions of temperature and gaseous atmosphere, a single microbial cell or clump of cells will multiply and form a visible colony that can be counted. This approach has advantages of simplicity and sensitivity but can involve long elapsed times before a result is obtained: 1-2 days for a standard plate count but longer to determine slower growing organisms or to detect specific pathogens such as Salmonella. Where a system of positive release is applied and products are not shipped out until laboratory results are known, this will mean increased storage costs for the manufacturer and a shorter shelf-life at the retail level and in the home.Traditional counting techniques also suffer from a large consumables requirement and are most irksome to perform. Consequently, there is considerable interest in methods that reduce labour and materials’ costs in addition to those which provide a result sooner. Although some techniques achieve both objectives, this is not always so, but both categories of improvement are generally subsumed under the title of rapid methods. Alternative strategies for the determination of the microflora in foods are presented in Table 2, with some examples of individual techniques. The HACCP approach consists of three stages: Table 2. Strategies for microbial determination in foods Microbial activity or components Microbial cells Colony formation Antigenic compounds Breed smear co* Electrical properties Redox dye reduction Ergosterol (Turbidity) Turbidity Lipopol ysaccharide Microbial metabolites ATP Coulter counter Chitin DEFT (LAL) Pyruvate Microbial Activity Measurements Electrical Properties When an alternating voltage is applied across a cell containing a microbial culture, it experiences a resistance to current flow termed the impedance, consisting of a resistance - conductance factor and a capacitance factor.As the microorganisms grow and metabolise they produce changes in these electrical properties that can be monitored and related to the original size of the microbial population.2 This is the basis of the rapid method most widely applied at present in the food industry. Although not so rapid as some other techniques, it does have the advantage of a large throughput of samples with minimal preparation time.Two commercial instruments are currently available, the Malthus, which monitors conductance changes, and the Bactometer, which can monitor impedance or, in later models, its conduc- tance or capacitance components. This facility, it is claimed, allows the selection of the parameter most appropriate for a given analytical problem. In a suitable medium, a plot of impedance or conductance against time has the same shape as a microbial growth curve, although the two are not superimposable. The point at which the first detectable change in electrical property occurs, termed the detection time, corresponds to a microbial population of 106-107 cfu ml-1. Hence the apparent lag phase will include a period of exponential growth. The detection time is inversely proportional to the logarithm of the inoculum size and, although correlation coefficients are often no better than 0.9, it is held that this is in large measure due to errors in viable counting procedures. In particular, electrical methods can be regarded as more accurate as individual cells and clumps of cells produce single colonies in a viable count whereas all metabolising cells contribute to reducing the detection time, just as they would to reducing the acceptability of a food.The time taken to obtain a result depends on the quality of the product-the larger the microbial population, the shorter is the detection time. Usually, a population of 10s cfu g-1 will have a detection time of about 8 h.Modern instruments can accommodate more than 500 samples and, once a protocol has been standardised, present the results using an unambiguous colour quality code of acceptable, marginal or unacceptable. The technique is usually applied to obtain the equivalent of total viable count data and for hygiene monitoring, but selective count procedures have been developed for, inter alia, coliforms, yeasts and a rapid salmonella pre-screen. Turbidity The automated monitoring of turbidity provides similar data to the Bactometer and Malthus instruments. The Bioscreen will monitor optical density periodically in up to 200 cuvette wells in an incubated plastic plate. The equivalent of a detection time is obtained with an optical density corresponding to a microbial level of about 106 organisms per millilitre.The technique differs from the electrical methods in that its sensitivity is reduced by opaque foods, which necessitate large dilution factors.3 Chemical Component Analysis-ATP Several components or metabolites of microorganisms have been identified as potential indices of microbial levels in food. Such approaches are attractive because usually they do not require a microbial growth stage and can thus be very rapid (<1 h). ATP, in particular, has received attention as it is common to all cellular life forms and can be assayed efficiently using the luciferin - luciferase reaction that is the basis of the bioluminescence of fireflies .4 The reaction has a high quantum efficiency, producing approximately 1 photon (A 560 nm) for every molecule of ATP, with a sensitivity, under practical conditions, of 102-103 fg ofANALYTICAL PROCEEDINGS.OCTOBER 1988. VOL 2.5 327 ATP. The average ATP content of a colony forming unit is normally 0.5-1 fg. The technique is very rapid, producing a result in less than 30 min. An important drawback, though, is the high levels of intrinsic ATP in many foods, which can outnumber microbial ATP by a factor of several thousand. One approach to this problem is the selective destruction of non-microbial ATP using an ATPase and a mild surfactant to disrupt somatic cells prior to the assay of microbial ATP. This has met with some success, but failure to destroy all non-microbial ATP can still cause problems at low counts and research efforts are being directed to this area.An alternative strategy is to separate the microorganisms from the food. This is particularly attractive with liquid foods that can be membrane filtered. In our own laboratories an ATP method capable of detecting 10-20 yeasts or 103-105 bacteria in 100 ml of pasteurised beer has been developed. The separation of microorganisms from solid foods presents greater difficulty, but centrifugation and ion-exchange resins have been employed with some success as pre-treat- ments for meat homogenates prior to membrane filtration and ATP assay. However, even in the event of the determination of exclusively microbial ATP problems can arise. In a mixed microflora yeast cells will contribute 100 times the ATP of bacterial cells and sub-lethally stressed organisms will contain very low levels yet be capable of recovery and growth in a food during storage.The need for very rapid tests to be applied at critical control points was mentioned earlier and it is here that ATP measurement offers particular promise. It can be used in the rapid assessment of the cleanliness of equipment, often without having to destroy non-microbial ATP, as the significance of ATP from organic soil would be similar to that of microbial origin. Microbial Cells-the Direct Epifluorescent Filter Technique (DEFT) Originally developed in environmental microbiology, the DEFT has been adopted for use with foods, particularly milk, with some success.5 By treating the milk with detergent and a proteolytic enzyme for 10 min it is possible to filter 2 ml of sample, thus improving on the sensitivity of the traditional Breed count by a factor of 100.A polycarbonate membrane filter is used to trap the bacteria in a single plane to facilitate counting. Acridine orange gives better staining than methylene blue, used in the Breed Count, as well as an indication of viability. Those cells or clumps of cells which fluoresce orange - red are taken as being viable while those which fluoresce green are presumed to be non-viable. The difference is thought to reflect the multiple binding of dye molecules to abundant RNA in viable cells against a predominant interaction with DNA in non-viable microorganisms. This interpretation is not always correct, as an orange fluorescence is observed with dead organisms in some heat-processed foods such as baked goods and pasteurised dairy products.The same pattern of fluorescence is observed in irradiated foods too, but in this instance it offers a potentially valuable test for the microbiological quality of the material before irradiation. Reasonable correlations with plate counts have been obtained for foods other than milk which are subjected to preliminary coarse filtration, although problems are sometimes caused by particulate matter interfering with counting. The technique has greater selectivity than ATP determination, enabling the microorganisms to be classified morphologically. Greater selectivity is available, albeit at the cost of reduced speed, through counting microcolonies on a selective agar after 3-6 h of incubation. References 1. 2. 3 . 4. 5 . Gray, J., Chem. Ind. (London), 1985, 136. Easter, M. C., and Gibson, D. M., Prog. Ind. Microbiol., 1988, 26, in the press. Mattila, T., J . Food Protect., 1987, 50, 640. Stannard, C. J . , and Gibbs, P. A., J . Biolumin. Chemilumin., 1986, 1, 3 . Pettipher, G. L. (Sharpe, A. N.. Series Editor), “The Direct Epifluorescent Filter Technique for the Rapid Enumeration of Micro-organisms,” Letchworth Research Studies Press. Letch- worth, 1983. Electron Spin Resonance Vol. 11A Senior Reporter: M.C.R Symons, University of Leicester Specialist Periodical reports are a series of review volumes, which provide critical coverage of major areas of research. Electron Spin Resonance is divided into two volumes ‘A’ and ‘B’ which are published in alternate years. The ‘A’ volume is devoted to organic and bio-organic subjects, and the ‘B’ volume to inorganic and bio-organic subjects. Electron Spin Resonance Volume 1lA reviews recent literature to mid-1987. Brief Contents: Organic Radicals in Solution; Theoretical Aspects of E.S.R. ; Spin Labels; Biological Membranes; Free Radical Studies in Biology and Medicine; E.S.R. of the Conformation of 5- and 6-Membered Cyclic Nitroxide (Aminoxyl) Radicals. An important feature of this volume is the special chapter on Nitroxide Radicals. It contains many previously unpublished results and will therefore be invaluable to researchers in this field. SPECIALIST PERIODICAL REPORTS (1988) Hardcover. 210pp. ISBN 0 85186 861 4 Price $69.50 ($139.00) RSC Members Price 330.00 ROYAL SOCIETYOF CHEMISTRY Information Services

ISSN:0144-557X    

DOI:10.1039/AP9882500324

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年代:1988

数据来源: RSC

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32s ANALYTICAL PROCEEDINGS. OCTOBER 1988. VOL 25 Alternative Methods for Trace Elements The following is a summary of one of the papers presented at a Meeting of the Analytical Division held on February loth, 1988, in the Scientific Societies Lecture Theatre, London W.1. Chemical Analysis at Solid Surfaces J. N. Ness and D. J. Joyner Unilever Research, Port Sunlight Laboratory, Quarry Road East, Bebington, Wirral, Merseyside L63 3JW The principal interests of most participants in this meeting clearly involved the study of trace materials in solution. We discuss here a range of techniques which concentrate on the surfaces of solid materials and complement the many tech- niques which study solution-phase materials. These surface sensitive techniques should be useful to the analyst interested in trace analysis because they can provide a range of information directly from the surface of a material “as-seen.” The surfaces of solid materials are very important in many branches of science.Physical and chemical properties of solids, such as their frictional behaviour, wear properties, dissolution, oxidation, etc., depend on the first few atomic layers of the solid. Also, the performance of catalysts is determined largely by chemistry taking place at this highly localised surface region. In view of this wide importance of the solid surface, it is not surprising that many techniques have been developed to study their physical and chemical properties. Surface analysis techniques generally involve the use of a “probe” to investigate the solid surface, and the detection of a “signal” emitted from that surface during the experiment, see Table 1.Most experiments of this type involve probes/signals which are low energy and/or charged, and which consequently interact strongly with matter. The experiments therefore need to be performed in a vacuum, which limits the type of sample that can be studied. The techniques which we have chosen to discuss are listed in Table 1. These fall into three categories: mass spectrometry, where the mass to charge ratios of surface-emitted ions are studied; electron spectroscopy, where the energy distribution of emitted electrons is measured; and microscopy, where surface structure and chemistry are studied at high magnifica- tion. The above techniques are by no means an exhaustive survey of surface analysis techniques, but our aim is to present a general overview of the types of chemical and structural information that can be obtained and how these categories complement one another.The information that can be obtained about surfaces from such techniques falls into the following categories: elemental identification; quantification; elemental mapping; chemical state; molecular groupings. We present below a series of examples which illustrate these categories. Quantification The techniques fall into three categories as far as quantification is concerned, fully quantitative, semi-quantitative and qualita- tive, and the breakdown by technique is shown in Table 1. These really indicate the difficulty of obtaining a quantitative surface determination. Those which are fully quantitative provide quantitative analysis routinely; the semi-quantitative techniques can provide quantitative information, although this is more difficult and usually requires careful calibration studies tuned to the problem in hand.Those which are listed as “qualitative” cannot, at the present- time, yield quantitative information, either because of theoretical or practical limita- tions of the techniques. Table 2 gives an idea of how little material may be detected and measured by the techniques that we are discussing. It is Table 2. Detection limits for the various analysis techniques Minimum Minimum Minimum volume detection detection sampledlm3 limit limitikg LIMA, LIMS 10-2” -1 p.p.m. 10-22 SIMS 10-23 Auger 10-2’ -0.1% 10-1” ESCA, XPS 10-13 -0.1% 10- 13 SEMIXRM 10-16 -0.1 Yo 10-15 TEM/XRM 10-24 -0.1% 10 23 1 atom STM - 100 atoms - -1 p.p.m.10-24 seen that the techniques all involve the analysis of very small amounts of material and may truly be considered as trace techniques. It is thus possible to analyse very small fragments of material or small areas of interest in a much larger sample. Most of the techniques have the practical limit that an element needs to be present at about the level of 0.1 to 1% (by number Table 1. The surface analysis techniques discussed in the text, quantification available Mass spectrometry LIMA, LIMS Electron spectroscopy Auger SIMS XPS, ESCA showing the nature of the probe Probe Photons Ions Electrons X-rays Electrons Electrons Elect r ~ n s Field Signal Ions Ions Electrons Electrons X-rays X-rays Electrons Electrons and signal used and the degree of Quantification Qualitative Semi-quant .Fully Quant . Fully Quant . Fully Quant. Semi-quant . Semi-quant . Qualitative Microscopy SEM/XRM TEM/XRM TEMiEELS STMANALYTICAL PROCEEDINGS. OCTOBER 1988. VOL 25 329 Table 3. A summary of the scope of the analysis techniques ESCA LIMA Periodic table Li- U H-U Lateral 3100 pm 2 2 pm Depth 3 3 nm 20.1 pm Isotopic N O Yes Chemical Yes No coverage Complete resolution resolution detection information time Point analysis -5 min -10us SIMS Auger TEMiXRM SEMiXRM STM H + U Li- U B + U B+U ? 2 1 lim 30.05 pm 210 nm 2 1 pm 20.1 nm 24 nm 3 1 nm 2 5 nm 230 nm Monolayer Complete Yes No No No No Yes Yes No No No -1 min -5 rnin -1 min -1 rnin -10s of atoms) in the sampled volume to make analysis practical.However, the mass spectrometric techniques of SIMS and LIMA are exceptions to this and are much more sensitive. providing analyses at p.p.m. or even p.p.b. levels. A general summary of the techniques is given in Table 3. Except for STM, which has been recently developed as a research tool, they may all be considered as analytical techniques, providing a wide range of information. Most elements can be analysed, but only the mass spectrometries can analyse hydrogen, which is particularly important, for example in metallurgy, where hydrogen is implicated in causing embrittlemgnt, and for organic compounds. The techniques cover a wide range of lateral and depth resolutions. ESCA investigates the largest sample area, TEM/EDS offers the highest resolution microscopy, and the depth resolution varies widely, from a single monolayer up to about 0.1 pm (LIMA).The isotopic detection capability of the mass spectrometries SIMS and LIMA is worth noting in view of the applications for isotope studies discussed in this meeting. Fig. 1. SIMS images from an Fe - A1 specimen. ( a ) , Ion-induced secondary image; ( b ) , Fe image; (c), A1 image; and ( d ) , B image. (Photographs courtesy of Kratos Analytical) The Techniques SIMS (Secondary Ion Mass Spectrometry) SIMS combines the abilities to obtain a high resolution image of the distribution of elements and molecular moieties across the surface and to detect surface species at high sensitivity. In the SIMS technique, various ion beams are available.The options of inert gases, reactive gases (e.g., oxygen) and liquid metal ion sources ( e . g . , gallium) are chosen to match the type of information required, for example, high mass resolution or optimum spatial resolution. A typical application of SIMS is the study of problem regions in an iron-aluminium alloy. In this application, high spatial resolution was needed to follow the distribution of various surface species, so the liquid gallium source was chosen. Fig. l(a) shows a physical image of the surface morphology, an ion induced secondary electron (ISE) image. This has fissures running top-right to bottom-left and an H-shaped structure at right angles to this. Fig. 2 shows the positive SIMS spectrum averaged over the area of the physical image, which displays iron and aluminium peaks of the alloy composition, but also shows sodium, potassium, calcium and boron.It is interesting to see how these elements are distributed, and the SIMS maps of Fig. l(b), (c) and ( d ) show, respectively, the iron, aluminium and boron distributions. The H-shaped feature is seen to have a high concentration of boron and iron but no aluminium, whereas the fissure structure is opposite to this, suggesting that the alloy problem is due to co-segregation of iron and boron. 100 I 8 ai c m -0 c 2 50 m a, > m a, U .- 4- - 0 10 20 30 40 50 60 AMU Fig. 2. sodium, 27 = aluminium, 39 = potassium, 40 = calcium, 56 = iron SIMS spectrum from the area of Fig. 1: 11 = boron, 23 = A second example (Fig.3) shows that SIMS can “finger- print” organic materials at surfaces. Figs. 3(a) and ( b ) show similar mass ranges for the negative ion SIMS spectra. Without detailed analysis it is clear that the mass clusters on these spectra give fingerprints for the molecular structure of the polymer at the surface. The positive ions are mainly silicon - carbon - hydrogen species and the negative ones carbon - oxygen - hydrogen. These can be compared with the patterns from well characterised mass spectrometry studies. This application shows the potential for obtaining chemical information in SIMS in addition to the elemental and mapping facilities illustrated earlier. LIMA (Laser Ionisation Mass Analysis) LIMA is another mass spectrometry technique and uses a laser as the exciting source.This generally probes much deeper than330 ANALYTICAL PROCEEDINGS. OCTOBER 1988. VOL 3 Si(CH3) 43 ~~ 0 20 40 60 80 100 120 140 160 180 200 AMU AMU 0 20 40 60 80 100 120 140 160 180 200 AMU AMU Fig. 3. of Kratos Analytical) SIMS spectra of polydimethylsiloxane polymer. (a>, ( b ) , Positive ion spectra; (c), (d), negative ion spectra. (Spectra courtesy the highly surface sensitive SIMS. Typically, the laser blast vaporises about 1 ym3 of sample, which provides the LIMA spectrum. This leaves a crater of the order of 1 ym diameter and 1 ym deep. Again, all the possibilities of a mass spectrometry technique are available. For example, the mass isotopes of elemental molybdenum can be clearly resolved (Fig. 4). The relative ion abundances in LIMA are in good agreement with tabulated values.Relative isotopic abundances as percentages of total Mo: rn Measured Tabulated 92 15.31 15.05 94 10.12 9.35 75 80 85 90 95 100 105 Mass number, rn Fig. 4. (Spectrum courtesy of Cambridge Mass Spectrometry) LIMA spectrum showing resolution of molybdenum isotopes. The attraction of LIMA is first that it is very rapid. A microanalysis can be performed in less than 1 s, and many spot analyses can thus quickly indicate variations across a surface. Secondly, ionisation mechanisms are different from those in SIMS, giving advantages for the analysis of some types of material. For example, insulating materials are often difficult by SIMS because they charge under ion bombardment and scatter the primary ion beam. With the neutral laser beam of LIMA this does not occur.Variations of ionisation mechan- isms for different types of materials sometimes mean that conditions can be set up in which only one or other component yields a LIMA spectrum, simplifying interpretation. ESCA (Electron Spectroscopy for Chemical Analysis) ESCA is a powerful technique for studying surface composi- tion and has the great advantage that it is essentially non-destructive because it relies only on electrons being ejected from the core levels of the surface atoms rather than on the ejection of particles. The energy of the photoelectrons is measured to high precision and often allows the chemical state (oxidation state) to be determined. As the emitted electrons interact with the other electrons on their traverse through the material under study, the ESCA peaks contain much informa- tion on the electronic structure of solids.For example, information on the electronegativity of atoms bonded to those under study, on the magnetic state of the atoms, etc. The technique is sensitive to the first several atomic layers of the surface, and this depends primarily on the kinetic energy of the emitted electrons. A typical ESCA spectrum of a steel sample is shown in Fig. 5(a). Several peaks are obtained for each surface element, e.g., Fe 2p, 3s and 3p. It can be seen that by using different photon energies the kinetic energies of the emitted electrons can be varied, and thus greater or lesser depths within the material sampled. Such techniques allow “non-destructive depth profiling” of the depth distribution of different elements within the surface regime between 1 and 15 nm. Another way to increase the depth penetration of the technique is to remove the surface layers sequentially by ion bombardment, in a “billiard-ball” manner. Recording ESCA spectra between each successive sputter then provides a “depth profile” of the material.For the steel sample mentioned above, Fig. 5(b) shows such a depth profile. Looking at the energy region where we expect to see chromium (Cr 2p) we find very little before any surface cleaning (scan 1) and after the first ion bombardment session of 2 min (scan 2). However, after this the Cr peak emerges as the surface contaminant layer is removed. The energy of the peakANALYTICAL PROCEEDINGS. OCTOBER 19x8.VOL 29 33 1 50 000 40000 $ 30000 >. v) C Y I 4- .- g 20000 a, C 4- - 10 000 0 L..ll Iron 800 600 400 200 Binding energyleV v) K 3 4- 8 60000 1 >. 4- .- 40000 a, C 4- - 20 000 0 A \ \ L- 595 590 585 580 575 570 Binding energylev Fig. 5. ESCA spectra from a steel sample. ( a ) , Wide (energy) Scan of surface; ( b ) , depth profile of chromium peak in scan 3, however, is characteristic of completely oxidised chromium. After two more sputters (at scan 5 ) another Cr peak at lower binding energy emerges. This is metallic chromium, indicating that the surface oxide layer is nearly removed, and indeed the next layer (scan 6) comprises only the metallic chromium species. AES (Auger Electron Spectroscopy) This is a technique closely allied to ESCA, but involves a more complicated, three-electron process. It has the advantage that the Auger transition can be excited by electrons which are strongly focusable, providing the possibility of elemental and chemical mapping at very high resolutions (down to -100 nm) and with very high surface sensitivity.The technique thus complements many aspects of the techniques noted above, and has found wide application in metallurgy and semiconductor research, although it presents problems of sample damage and charging by the energetic electron beam for more delicate materials. EM/XRM (Electron Microscopy/X-ray Microanalysis) Electron microscopy is a familiar technique and provides topographic and structural images at high spatial resolution. Two forms of microscopy are commonly encountered.Scan- ning electron microscopy (SEM) utilises a small scanning probe of electrons to form an image of the surface topography of samples at high resolution (typically up to 5 nm). Transmission electron microscopy (TEM) is used to image directly thin specimens at very high resolution (up to -0.2 nm). The incident electron beam produces a variety of signals, including X-rays characteristic of the elements present in the sample, and these are utilised in various X-ray microanalysis techniques to provide elemental identification, quantification and location Energy dispersive spectroscopy (EDS) is the most common technique and uses parallel detection to provide rapid elemen- tal identification. The original, but less common, wavelength dispersive (WDS) technique is used where greater resolution (mapping).and accuracy are required. The combination of EM with these techniques provides the useful ability to correlate elemental composition with topographical features at high resolution (-0.1 pm SEM, 10 nm TEM). Elemental maps can be produced in a similar manner to SIMS and chemical informa- tion is also present to some extent in the WDS spectrum. It is also possible to measure the energy of the transmitted electrons in the TEM and form an electron energy loss spectrum (EELS). This form of spectroscopy is capable of providing some chemical information (e.g. , nearest neigh- bours, bond distances) as well as simple identification and quantification. STM (Scanning Tunnelling Microscopy) This recently developed technique is included because it potentially offers the possibility of identifying single atoms at a surface. The technique relies on the fact that, if an electrically biased, atomically sharp tip is brought very close (<1 nm) to a conducting surface, then electrons will be able to tunnel from the specimen to the tip. The tip can then be scanned over the surface of the specimen to produce either a topographic map (tunnelling current is held constant) or a “work function” map (tip to sample distance is held constant). It is the latter of these two modes that provides the possibility of identifying single atoms, as the microscope can perform at very high resolution (-0.1 nm laterally and -0.001 nm in depth). Conclusions This review has illustrated that there are various techniques available for surface analysis which provide complementary information and allow one to tailor the technique to the sample and the information required. Various sorts of information are available, viz. , qualitative identification, quantitative analysis, elemental distribution, chemical state and chemical grouping. The techniques can sample very small amounts of material (10-z4 kg or less) and thus can be considered to be trace element techniques (with the proviso that elements must be segregated to the surface or interface of interest).

ISSN:0144-557X    

DOI:10.1039/AP9882500328

出版商:RSC    

年代:1988

数据来源: RSC

摘要:

332 ANALYTICAL PROCEEDINGS. OCTOBER 1988. VOL 35 Databases for Analytical Chemists The following is a report of a Joint Meeting of the South East Region and the Chemical Information Group of the RSC held on March 23rd, 1988, in the BP Research Centre, Sunbury on Thames. Databases for Analytical Chemists G. F. Phillips DeDartment of Trade and Industry, Laboratory of the Government Chemist, Cornwall House, Waterloo Road, London SE I 8XY On March 23rd the RSC Chemical Information Group and the South East Region of the RSC Analytical Division jointly arranged a meeting on the use and availability of computerised databases for analytical chemists. The British Petroleum Research Centre kindly provided the venue and excellent catering for the meeting and facilities for on-line demonstra- tions.In the Chairman’s introduction, Geoffrey Phillips referred to the following needs: of the analyst, to validate methods, verify the data and confirm the proper working of any computer relied upon; of organic chemists, for codified structural information; for machine recordable bibliographic records and physical data compilations; and for directories of chemical, biological, radiological and epidemiological hazards. The general information requirements of the analyst were comprehensively set out by Harry Shalgosky, Head of the Environmental and Medical Sciences Division at the Harwell Laboratory and Chairman of the Analytical A bstracts Editorial Committee. Measuring elemental concentrations is only one facet of analysis, with sampling, matrix problems, distinguish- ing isomers, isotopes or molecular species and choice of technique all complicating the situation.To avoid “reinventing the wheel” he recommended consulting commercial encyclo- paedias of formulations, critical reviews in Analytical Chem- istry or structured searches in abstracts such as Analytical Abstracts (available since 1954). He contrasted the number of citations that reviewed XRF in 1950 (13) with those in 1987 (340). Where such information is on-line, an Information Officer can search about half a million references in 8 min using Boolean logic. But many more “grey” sources need to be browsed manually, such as university theses, commercial “handbooks” of thermodynamic data or reports of synthetic routes or laboratory hazards, if the prior art and optimum solution to the analytical problem is to be fully researched.David Spender, Head of Sales and Marketing for Orbit Search Service (part of Pergamon Orbit Infoline), responded by reviewing the growing variety of currently available retrieval systems; there are more than 1000 on-line databases, including educational and geographical material. The enor- mous and constantly growing database of Chemical A bstracts (8 000 000 items since 1967) became accessible, and off-line printable, by collaboration with the United States’ defence programme. World-wide access to this database is now possible by cheap data links and packet switching systems. Analytical Abstracts has a bibliographic structure with 90 000 records since 1980. The Water Research Centre system, “Aqualine,” has 109000 items from 1960 covering all aspects of aqueous effluent and disposal, while Food Science and Technology Abstracts has one third of a million nutrition and packaging records from 1964.In the environmental context the data base “Eviroline” has 129 000 health and monitoring reports from 1971 and “HSE-LINE” has 90 000 items since 1977 document- ing United Kingdom factory trends; for the USA, the NIOSHTIC data base provides 140 000 references back to the 19th century. For specialised industries, RAPRA lists 265 000 rubber polymer entries from 1972 and the World Surface Coatings Abstracts has 114 000 since 1976. While at present the on-line hosts preferred Information Officers to search from a central point, they sought to make their systems more user friendly and ultimately looked to there being terminals in every laboratory section, using mouse-driven split-screen menus in general searches.RSC Nottingham provided a double act. First, Debbie Walker, Senior Marketing Officer, dealt with the content and accessibility of the “CAS ONLINE” database available through STN International. The complete bibliographic data are available from 1967 and the 8 000 000 items are growing by about 450000 per year. The “CA Old” database has worked backwards and is coding the accession numbers which, when retrieved, have to be looked up in hard copy of the older CA. Related facilities include “CA-Previews,” which provides six weeks anticipation of what will then appear in CAS, and the CAS Registry file, which has information on all compounds listed since 1962 and is growing by about 10 000 items per week.Coming attractions are “CASREACT,” which is expected to appear in 1988 and will list organic reactions reported in CA since 1985, and “STN Express,” scheduled for late 1988, which will enable building a search structure off-line with “templates” and predefining a search strategy “hedge” before undertaking the search on-line. (A copy of a booklet relating to this and a specimen floppy disc can be supplied.) Over 70% of CA is from world journals but 15% arises in patents and 13% in the “grey” literature such as dissertations, books and conference proceed- ings. Roughly 5% of the whole CA covers analytical topics across the board but four of the eighty sections are of a special interest to analysts: S9 (biochemistry), S64 (pharmaceutical analysis), S79 and 80 (inorganic and organic analysis). Phil Read, Deputy Product Manager for Analytical Abstracts, described its content and means of access.AA is unique in the western world: its main content (98%) is 300 primary journals which are covered regularly, supported by occasional papers from a further 1000, written in over 20 original languages and from all five continents. The entries in AA present much more than the author’s abstract by including applicability, precision, experimental details and index features. It is possible to focus the search through the determinand (using appropriate approved, e.g., BP or ISO, names), and the matrices and samples. At present “AA Online’’ has over 55 000 reports since 1984 and is increasing by more than 1000 per month.The AA backfile covers the years 1980-1983 in over 48000 records. The three on-line hosts are Orbit, Dialog and DataStar; the RSC runs workshops to assist both the novice and the experienced searcher.ANALYTICAL PROCEEDINGS, OCTOBER 1988. VOL 25 David Cameron, a laboratory head with BP America, described archiving physical and chemical (especially molecu- lar and atomic spectroscopic) data. His safety hints included the need for re-winding magnetic tape spools completely once a year, keeping them for 15 years and having a complete back-up file stored off-site. Each algorithm can be verified by the use of known data and, of course, data- time - name records are retained. Advantages include: integrity of data for regulatory or patent purposes; savings in book-keeping manpower; electronic transfer between remote laboratories, even world- wide; ability to hold a vast raw data store over one gigabyte; more instrument availability; and better data analysis, e.g., detecting subtle phase changes in spectra, deconvolution, curve fitting, subtraction or multiple-order derivatives.He looked to foster terminal systems that were suitable for rapid decision making and improved menu systems with quick exits. Chemical Hazard information systems were described by Sheila Pantry, the Head of Information Services for HSE. Classical off-line sources include lists of Codes of Practice and of Statutory Instruments, tables of safe exposure limits, catalogues of safety films and videos and a wide choice of text-books and encyclopaedias; in this last connection it was noted that the current edition of Sax weighs 15 Ib! On-line provision includes the CIS abstracts from ILO Geneva; Chemical Hazards in Industry (from Orbit); Laboratory Hazards Bulletin (from Orbit or Datastar); Excerpta Medica (Dialog and Datastar); the Barbour Index (for legislation and a wide range of information from HSE on microfiche); and use 333 of Prestel (with current HSE information) and the Hazchem Warnings (Harwell).She particularly drew attention to the publically available HSELINE database with 100 000 current references, growing by 12 500 per year, taken from worldwide sources. HSE research is also reported and great emphasis is laid on chemical hazards.This database is available from ESA/IRS, Pergamon Orbit Infoline and Datastar. So much information is now stored that HSE have adopted a Compact Disc system: a single CD-ROM with a capacity of 600 MB can carry the equivalent of 200000 A4 pages. HSE initiative brought together 3 major databases: HSELINE, NIOSHTIC (US) and CISDOC (ILO, Geneva). This CD (named “OSHROM” for Occupational Safety and Health Read Only Memory), produced by Silver Platter Information Service, was then demonstrated. Another CD system, CHEM- BANK, concatenates several US databanks, namely RTECS (with 60000 names and 50000 WLN structures), exposure standards for NIOSH and NCAIH, guidance on emergency spillages and the US Coastguard list (CHRIS) and toxicity or mutagenicity data. These CDs are updated quarterly and the on-line version monthly.Mrs. Walker (RSC) then demon- strated chemical searches on CAS database connected to STN International in West Germany and Phil Read showed use of “AA On-line” using a Nottingham connection. Altogether, this meeting provided a wide ranging and useful introduction to the variety of machine searchable data bases available to the analyst in Britain. , Analytical Applications of Spectroscopy I Edited by C.S.Creaser, Universify of East Anglia and A.M.C. Davies, Institute of Food Research, Norwich This new book provides a ‘State-of-the-Art’ review of the applications of the major spectroscopic techniques and will prove invaluable to researchers involved in this form of analysis. The book provides wide-ranging coverage of recent developments in analytical spectroscopy, and in particular the common themes of chromatography - spectroscopy combinations, Fourier transform methods and data handling techniques. Each section includes a review of key areas of current research, written by spectroscopists who have made major contributions in their respective disciplines, as well as short reports of new developments in these fields. These common themes have played an increasingly important part in recent advances in spectroscopic techniques and emphasise the multidisciplinary approach of present research. 502 pages ISBN 0 85186 383 3 1 Price E47.50 ($99.00) ROYAL ’G SOCIETYOF CHEMISTRY + hformation Services To order or for further information, please write to: Royal Soaety of Chemistry, Distribution Centre, Blackhorse Road, Letchworth, Herts SG6 IHN, UK. or telephone (0462) 672555 quoting your credit card details. We now accept Access/Visa/MasterCard/EuroCard. RSC Members are entitled to a discount on most RSC publications and should write to: The Membership Manager, Royal society of Chemistry, 30 Russell Square, London WClB 5DT, UK.

ISSN:0144-557X    

DOI:10.1039/AP9882500332

出版商:RSC    

年代:1988

数据来源: RSC

摘要:

334 ANALYTICAL PROCEEDINGS. OCTOBER 1088. VOL 25 Equipment News Spectrometers The PU9800 Series of Fourier transform infrared spectrometers offer good control and data manipulation facilities through an AT-compatible P3202 computer oper- ating the makers’ EAGLE infrared soft- ware. With a 45 Mbyte hard disk, the corrosion resistant sample introduction system, which allows concentrated solu- tions of hydrofluoric acid to be sampled. Coupled with the Elan 500’s new hard- ware is an enhanced software package. OmniRange permits the determination of major, minor, trace and ultra-trace ele- Philips Analytical PU9800 Series FTIR P3202 offers fast computing, high storage capability and access to standard IBM environment business software pack- ages. Philips Analytical, York Street, Cam- bridge CB1 2PX.Spectrometers The PV8060 Series of inductively coupled plasma optical emission spectrometers allow flexible elemental analysis in simul- taneous, sequential and combined operat- ing modes. Systems are available in both dedicated ICP and dual excitation spark/ ICP versions. These cover a standard wavelength range of 165485 nm in the first order, while an optional long wavelength polychromator gives access to further lines that are optional for the alkali elements. With element channels and a programmable scanner employing the same high-performance optics, pro- grams can be assembled for the integrated determination of routine and non-routine elements. Philips Industrial and Electro-acoustic Systems Division, I & E Press Office, Building HKF, 6500 MD Eindhoven, The Netherlands.Spectrometer The Elan 500 inductively coupled plasma mass spectrometer incorporates numer- ous analytical benefits over earlier systems. Used for low-level multi-ele- ment determination of elemental and isotopic species, it features enhanced mass spectrometer resolution and abun- dance sensitivity performance. Platinum sampler and skimmer cones, which lead to substantially longer orifice lifetimes, are standard equipment. Also standard is a ment concentrations in the same ana- lytical run. The Elan 500 meets FCC certification requirements for RF radia- tion emission. Perkin-Elmer Ltd., Post Office Lane, Beaconsfield, Buckinghamshire HP9 1QA. Gas Chromatograph The PU4400 is optimised for capillary analysis, yet guarantees excellent per- formance in conventional packed-column chromatography.Parameter setting and entry are straightforward and other func- tions are easily accessed, most of them by means of a single key. Other enhance- ments include a stopwatch, flow calcula- tor, auto-start and parameter locking facility. Two capillary injectors, one split - splitless and the other a program- mable thermal vaporiser injector, give excellent performance. Additional injec- tors are available. Five types of detector are offered, all optimised for capillary chromatography. Philips Analytical, York Street, Cam- bridge CB1 2PX. Silica Gel for Chromatography A reversed phase CI8 version of the makers’ flash chromatography grade sil- ica gel is now available. Sorbsil C40-60 RP18 is based on silica gel with a 6 nm mean pore diameter and 40-60 pm par- ticle size.It is intended to separate polar compounds which cannot be handled by naked silica. Sorbsil silica gels for flash chromatography are part of a range of chromatography media marketed under the brand name, Colpak. Particle sizes range from 5 pm up to 6&210 pm. May and Baker Ltd., Liverpool Road, Eccles, Manchester M30 7RT. Software for Gas Chromatography Using newly developed software, the Shimadzu Chromatopac C-R4A integra- tor can now take total control of a GC-14A gas chromatograph and auto- sampler by means of the current loop or RS 232C interface. All the GC paramet- ers can then be aibplayed on the integra- tor’s VDU for monitoring or updating. Temperature programming can be planned on-screen and represented graphically.During analyses the C-R4A displays chromatograms (single or dual channel) while maintaining control over the GC. Dyson Instruments Ltd., Hetton Lyons Industrial Estate, Hetton, Houghton le Spring DH5 ORH. HPLC Column Oven Through design changes and the use of modern, lower priced components the makers of the Model 750120 HPLC col- umn oven have been able to lower the price significantly. The oven goes up to 150°C with a temperature accuracy of +0.2”C. Up to six 60-cm columns can be accommodated. Applied Chromatography Systems, The Arsenal, Heapy Street, Macclesfield, Cheshire S K l l 7JB. Detector for Chromatography The LSD laser light scattering mass detec- tor for HPLC or GPC offers detection limits of 20 ng with squalene test mix- tures.Using a dual gas flow nebulising inlet, evaporation of the mobile phase is achieved forming small particles of non- volatile solute. The nebulising gas stream carries these through a photodiode detec-ANALYTICAL PROCEEDINGS. OCTOBER 1988. VOL 25 3.35 tor, which measures the light scattered from the particles. Kemtronix (UK) Ltd., Axis House, Compton, Berkshire RG16 ONL. Detector for HPLC The RI SE-61 is a compact, micropro- cessor-controlled refractive index detec- tor featuring low noise, high stability and small dead volume. It incorporates the ability to compensate automatically for a decrease in sensitivity caused by stains on the flow cell. The primary areas of appli- cation include the measurement of samples which have no ultraviolet absorp- tion, measurement using any eluent that has ultraviolet absorption and the measurement of the molecular weight distribution of polymer samples.For gel- permeation chromatography the SE-61 can be used with the makers’ low-noise solvent delivery system and range of GPC columns. Severn Analytical Ltd. , 36 Brunswick Road. Gloucester GL1 1JJ. Detector for HPLC Based on diode-array technology, the LC-135 dual wavelength programmable ultraviolet detector provides precise wavelength selection and instantaneous wavelength change without moving parts, thus ensuring that wavelength accuracy and reproducibility are not compromised through mechanical wear. It can be used in a universal ultraviolet mode, detecting all ultraviolet absorbing species regard- less of the monitoring wavelength for method development. With the addition of a printer - plotter the LC-135 can calculate and output peak purity, ratio- grams and the wavelength of maximum absorbance for peak identification, peak tracking or for wavelength switching pro- grams.Perkin-Elmer Ltd., Post Office Lane, Beaconsfield, Buckinghamshire HP9 1QA. Solvent Delivery for Liquid Chromatography The stand-alone System Gold delivery modules (Model 116 isocratic and 126 gradient) offer flexibility of application. A flow-rate change of 1 pm to 10 ml min-1 can be obtained from each module (1 1.11 to 20 ml min-1 isocratic for the Model 126) with reproducibility of +_O.l”/o and maxi- mum operating pressure of 6000 Ib in-2. Each module provides complete time programmability of flow-rate, solvent selection facilities and six standard con- tact closures.Beckman, Progress Road, Sands Indus- trial Estate, High Wycombe, Bucking- hamshire. Microplate Reader The Denley Anthos Labtec 2001 pho- tometer and data reduction instrument for microplate reading is capable of per- forming colorimetric, nephelometric and agglutination assays without instrument modification, and it allows simultaneous multiple wavelength measurements for research and special clinical applications. Five different measurement modes for single or dual wavelength, agglutination readings, kinetic measurements with true 5 s reading intervals, multiple wavelength readings and as a totally remote con- trolled photometer are offered. Denley Instruments Ltd., Natts Lane, Billingshurst, West Sussex RH14 9EY.Recorder for pH Measurement pH can be recorded directly from Kent or other compatible sensors by the PlOOS/P strip-chart recorder, which enables values in the range 0-14 pH to be monitored and recorded with a continuous trace on a 100-mm wide chart. A choice of manual or automatic temperature compensation is offered. Kent Industrial Measurements Ltd. , Howard Road, Eaton Socon, St. Neots, Huntingdon, Cambridgeshire PE19 3EU. Total Nitrogen Analyser The TN-05 from Mitsubishi is designed for automatic analysis of total nitrogen in liquid samples. Using catalytic oxidative pyrolysis and chemiluminescence detec- tion, it has high sensitivity and broad sub-classes, showing a higher affinity for monoclonal and polyclonal IgG sub- classes than Protein A.Protein G can be supplied for use in affinity chromato- graphy or HPLAC as Protein G-agarose or as a SelectiSpher-10 Protein G column. For most immunoglobins binding occurs under physiological conditions, that is, neutral pH and low ionic strength. The recovery of antibodies is therefore very high. High-purity horseradish peroxidase bound to Protein G can also be provided; it is suitable for enzyme immunoassay of antigens or antibodies and for use in blotting procedures. EDT Analytical Ltd., 14 Trading Estate Road, London NWlO 7LU. Trace Oxygen Analyser Teledyne’s TURBO2 is a compact, easy- to-use trace oxygen (0,) analyser offering p.p.m. sensitivity and providing spot checks on the gas phase oxygen content of a wide variety of industrial gases and gas mixtures.It features three measuring ranges of 0-100, 0-1000 and 0-10000 p.p.m. 02. ACAL Auriema Ltd., 442 Bath Road, Slough SL16BB. Ultrafiltration - Microfiltration Unit The PES/OSMO - 10T - UF ultrafiltra- ivitsubishi TN-05 total nitrogen analyser (ED T Analytical) linearity down to 0.01 p.p.m. Each analy- sis is completed in 1-5 min with a pre- cision typically of k3% relative. It han- dles all aqueous and non-aqueous samples and gives total recovery of essentially all nitrogen species. Sample size can be from a few 1.11 to 60 ml. EDT Analytical Ltd., 14 Trading Estate Road, London NWlO 7LU. Protein G A complete range of Protein G reagents, manufactured by Perstorp Biolytica of Sweden, are available. They bind with high affinity to a broad spectrum of IgG tion - microfiltration Mini-lab is a sani- tary lab-scale unit using ultrafiltration and microfiltration spiral-wound sepralators (membrane elements) to provide com- prehensive scale-up data and perform small-scale production runs.It features sanitary 316 stainless-steel construction and a stainless-steel pump for high tem- perature operation to 82 “C with an oper- ating pressure range of 138-689 kPa and high flow-rates of 150 1 min-1. The unit operates in either batch or continuous mode. Osmonics Inc., 5951 Clearwater Drive, Minnetonka, Minnesota 55343, USA.336 ANALYTICAL PROCEEDINGS. OCTOBER 1988. VOL 25 Pipette The Microtip Liquipette is the latest member of the makers’ disposable Pas- teur pipette range and has been designed for the transfer of small samples.It delivers a consistent drop size of 20 pl. A catalogue is available. Elkay Laboratory Products (UK), Unit 2, Crockford Lane, Basingstoke, Hamp- shire RG24 ONA. Literature Two brochures describe the PRISM Series I1 stable isotope ratio mass spec- trometer and a range of sample prepara- tion systems. The PRISM Series I1 pro- vides high precision and sensitivity and, being controlled by the IBM PS/2 micro- computer, is easy to use. The sample preparation systems are compatible with each of the makers’ stable isotope ma:: spectrometers and they provide methods, often fully automated, for preparing and purifying sample materials prior to intro- duction into the mass spectrometer. VG Isogas Ltd., Aston Way, Middle- wich, Cheshire CWlO OHT. A brochure gives details of a range of hand-tight HPLC columns and access- ories which enable the use of columns with minimum effort.Designed by Professor John Knox of Edinburgh Uni- versity and originally manufactured and sold by Shandon Southern Ltd., these products are now made and exclusively sold by HPLC Technology. HPLC Technology Ltd., Wellington House, Waterloo St. West, Macclesfield, Cheshire SKll 6PJ. A brochure describes NuSep quick solid phase extraction disposable columns and NuGel Affinity-Pacs (disposable affinity columns). Applications of NuSep col- umns include sample enrichment, isola- tion and purification of interleukins, recombinant proteins, monoclonal anti- bodies, drugs, enzymes, hormones, nucleotides, pesticides, PCPs and inter- ferons. NuGel columns are for IEA, enzyme immobilisation and highly spe- cific purification of monoclonals and recombinant proteins. Camlab Ltd., Nuffield Road, Cam- bridge CB4 1TH.Siotext is a new, free, quarterly publica- tion for life science chromatographers. The first issue features the Progel TSK Phenyl 5-PW HPLC columns, which are ideal for isolating different types of proteins in enzyme resolution. Other articles are BPAs Enhance Separation and Purification of Pig Heart LDH and MDH, Sample Extraction and HPLC Analysis for Plasma Levels of Catechol- amines and Rapid Purification of Cal- modulin Using Hydrophobic Interaction. Supelco Inc., Supelco Park, Bellefonte, PA 16823-0048, USA. A brochure describes preparative HPLC on the Shimadzu LC-8A, giving full details of operational modes and of options for upgrading the LC-8A into a fully automated gradient system. Dyson Instruments Ltd., Hetton Lyons Industrial Estate, Hetton, Houghton le Spring DH5 ORH. A free guide to determining the water content of substances by the Karl Fischer titration method is now available. Radiometer Ltd., The Manor, Manor Royal, Crawley, West Sussex RHlO 2PY. A brochure on the CI 4000 protein sequencer provides comprehensive infor- mation on the CI 4000 and on the ac- cessories available. A full set of results is included. Chelsea Instruments, Unit 9, Avon Business Centre, Avonmore Road, Lon- don W14 8TS. Three brochures on the AMS range of image analysis and automated microscopy equipment are available. A general range brochure describes the image analysis systems and complementary products available for image processing and auto- mated microscopy. It includes details of the 40-10 automatic analyser and of the VIDS V and the full VIDS series of interactive analysers. A second brochure gives details of the Quickstep automatic stage control system. The third describes the Measuremouse Amstrad PC compat- ible image analyser. Analytical Measuring Systems, London Road, Pampisford, Cambridge CB2 4EF.

ISSN:0144-557X    

DOI:10.1039/AP9882500334

出版商:RSC    

年代:1988

数据来源: RSC

摘要:

336 ANALYTICAL PROCEEDINGS. OCTOBER 1988. VOL 25 Publications Received Polymer Surface Dynamics. Edited by J. D. Andrade. Pp. viii + 182. Plenum Press. 1988. Price $49.50. ISBN 0 306 42788 5. Computational Chemistry. An Emphasis on Practical Calculations. Milton D. Johnston, Jr. Studies in Physical and Theoretical Chemistry, 56. Pp. xviii + 680. Elsevier. 1988. Price Dfl245; $129 (hardback): DflllO; $58 (softback). ISBN 0 444 42962 X (hard- back); 0 444 42963 8 (softback). Analytical Isotachophoresis. P. BoEek, M. Deml, P. Gebauer and V. Dolnik. Electrophoresis Library, Volume 1. Pp. xviii + 237. VCH. 1988. Price DM156; f57. ISBN 3 527 26444 2; 0 89573 477 x. Supercritical Fluid Extraction and Chro- matography. Techniques and Applica- tions. Edited by Bonnie A. Charpentier and Michael R.Sevenants. ACS Symposium Series 366. Pp. x + 253. 1988. Price $59.95 (USA and Canada); $71.95 (Rest of World). ISBN 0 8412 1469 7. Immunoassays for Veterinary and Food Analysis-1. Edited by B. A. Morris, M. N. Clifford and R. Jackman. Pp. xxxvi + 392. Else- vier Applied Science. 1988. Price f54. ISBN 1 85166 138 7. Water Analysis. A Practical Guide to Physico-Chemical, Chemical and Micro- biological Water Examination and Quality Assurance. Edited by W. Fresenius, K. E. Quentin and W. Schneider. Pp. xxvi + 804. Springer-Verlag. 1988. Price DM148. ISBN 3 540 17723 X; 0 387 17723 X. Secondary Ion Mass Spectrometry. SIMS VI . Edited by A. Benninghoven, A. M. Huber and H. W. Werner. Pp. xxviii + 1078. Wiley. 1988. Price f75. ISBN 0 471 91832 6. Analytikum. Methoden der Analytischen Chemie und Ihre Theoretischen Grund- lagen.7 Auflage. Edited by K. Doerffel and R. Geyer. Pp. 615. VEB Deutscher Verlag fur Grundstoffindustrie, Leipzig. 1987. Price DM55. ISBN 3 342 00191 7. Manual of Pesticide Residue Analysis. Volume 1. Edited by Hans-Peter Thier and Hans Zeumer. Pp. xvi + 433. VCH. 1987. Price DM128. ISBN 3 527 27010 8. Supercritical Fluid Chromatography. Edited by Roger M. Smith. RSC Chro- matography Monographs. Pp. xii + 238.I AN IMPORTNT NEW BOOK FOR CHROMATOGRAPHERS... SUPERCRITICAL FLUID CHROMATOGRAPHY Edited by Roger M. Smith Loughborough University of Technology Supercritical Fluid Chromatography is part of an important new series from the Royal Society of Chemistry entitled ’RSC chromatography Monographs’and is the first book devoted entirely to this rapidly expanding analytical technique. SFC is the current focus of attention in the Chromatography world and promises to revolutionise analytical procedures in the petroleum, pharmaceutical, food, agrochemical and biotechnology industries.This new publication will provide practising chromatographers in both industry and academia with a perspective on its principles, practice and potential applications. The book discusses the origins and development of SFC, the instrumentation that has been used and the technique’s growth from the related methodologies of GLC and HPLC. It also covers in great detail the way in which the separations in SFC can be altered to increase selectivity, compares the roles of packed and capillary columns and covers the coupling of SFC to mass spectrometry.Written by a team of acknowledged experts in the field, Supercritical Fluid Chromatography will prove invaluable to all scientists from government, industry and academia with an interest in SFC ISBN 0 85186 577 1 Hardcover 250pp. Publication date: April 1988 f27.50 ($59.00) RSC Members price f18.50 Discount price for this title, for customers wishing to place a standing order is f20.00 ($43.00) \ Don’t be without this imprtant publication. Payment by credit card is now accepted - ACCESS/MASTERCARD/EUROCARD/VISA ROYAL SOCIETY OF CHEMISTRY Non-RSC Members should order from: Royal Society of Chemistrv, Distribution Centre, & Blackhorse-Road, Lekhworth, He& SG6 1 HN, United Kingdom. *& RSC Members should order from: lnformat ion Membership Manager, Royal Society of Chemistry, c-.. l l P d C 30 Russell Square, London WC1 B 5DT, United Kir ‘- r338 ANALYTICAL PROCEEDINGS, OCTOBER 1988. VOL 25 Royal Society of Chemistry. 1988. Price Press. 1987. Price $39.95. ISBN 0 12 Monitoring. Volume 2. f27.50 ($59). ISBN 0 85186 577 1. Edited by J. Angerer and K. H. Schaller. Pp. xviii + 252. VCH. 1988. ISBN 3 527 Analytical Gas Chromatography. Analyses of Hazardous Substances in Bio- 27012 4 (VCH Verlagsgesellschaft) ; Walter Jennings. Pp. x + 259. Academic logical Materials. Methods for Biological 0 89573 647 0 (VCH Publishers). 384355 3.

ISSN:0144-557X    

DOI:10.1039/AP9882500336

出版商:RSC    

年代:1988

数据来源: RSC