ISSN:0144-557X    

DOI:10.1039/AP98017FX041

出版商:RSC    

年代:1980

数据来源: RSC

ISSN:0144-557X    

DOI:10.1039/AP98017BX043

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

ANPRDI 17(11) 457-506 (1980) ISSN 01 44-557X November 1980 Hon. Secretary P. G. W. Cobb Proceedings of the Analytical Division of The Royal Society of Chemistry AD President L. S. Bark Hon. Treasurer J. K. Foreman Hon. Assistant Secretary D. 1. Coomber, O.B.E. Hon. Publicity and Public Relations Officer Dr. A. Townshend, Department of Chemistry, University of Hull, Hull, HU6 7RX Secretary Miss P. E. Hutchinson Zditor, Analyst and Analytical Proceedings P. C. Weston Assistant Editors Mrs. J. Brew, R. W. Hazell, R. A. Young Publication of Analytical Proceedings is the responsi- bility of the Analyst Publications Committee: J. M. Ottaway (Chairman) W. H. C. Shaw H. J. Cluley D. Simpson ‘P. Gray J. M. Skinner J. N. Miller A. Townshend G. E. Penketh ‘P. C. Weston T. 6. Pierce J.Whitehead ‘Ex officio members All editorial matter should be addressed to: The Editor, Analytical Proceedings, The Royal Society of Chemistry, Burlington House. Piccadilly, London, WlV OBN. Telephone 01 -734 9864. Telex 268001. Advertisements: Advertising Department, The Royal Society of Chemistry, Burlington House, Piccadilly, London, W1V OBN. Telephone 01 -734 9864. @ The Royal Society of Chemistry 1980 Editorial The SRC and Analytical Chemistry The many recent discussions on the need to improve the quality, and perhaps also the quantity, of graduates well versed in the theory and practice of analytical chemistry have had some pleasing results. New academic posts and new courses have been set up at several univer- sities, and the initial response of school-leavers is rumoured to be good.In the longer term, however, the credibility of analytical chemistry as a genuine academic discipline will depend less on such developments than on the growth of the subject a t postgraduate level. Flourishing research groups and viable MSc courses will not only produce the specialists required in industry and the public service, they will also generate the teachers of the future and provide the means by which the status of the subject is compared with other branches of chemistry. Indeed, it is hard to envisage high-quality undergraduate or postgraduate analytical courses being taught in Departments lacking active research teams. The role of the Science Research Council in the development of our subject is thus crucial; although nominally concerned only with the funding of postgraduate work, the SRC will, in practice, exert a significant influence on the development of undergraduate analytical chemistry. In principle, postgraduate study at UK universities is funded by the “dual support’’ system, the Research Councils and the University Grants Committee (through the Universities) providing support of different types and a t different phases of the development of a research team.In practice, this system has virtually collapsed ; many universities have to struggle merely to maintain their commitments to undergraduate teaching, and the Research Councils are prevented by lack of money from supporting some of their highest-graded appli- cations for grants. In these rather unhopeful circumstances the SRC’s recent and new-found interest in analytical chemistry can only be welcomed.This interest was first manifested by the establishment of the Analytical Science Panel. 457458 THE “CONFERRING CHEMIST” Anal. Proc. The use of the term “Analytical Science” rather than “Analytical Chemistry” was judged to be significant, indicating the importance of analysis in a very wide range of subjects (clinical chemistry, environmental science, health and safety), as well as its rapidly growing links with electronics and other disciplines. Academic analysts could only be pleased and relieved that the SRC had awoken to something that many of us had realised for a long time! (.4 curious feature of the Panel was that apparently no senior academic in the analytical field was a member of it-it is hard to imagine this happening in any other branch of chemistry.) The Panel identified the causes of academic neglect of analytical chemistry and noted that the over-all level of research activity in univer- sities is low.No doubt this is true-though again it seems possible that the Panel was only partly aware of much research (especially in biomedical and environmental analysis) funded by other Research Councils, Government Departments and industry. The relationship between analytical chemists researching in the universities and the SRC is thus rather uneasy, the SRC perhaps underestimating the amount and quality of research undertaken, and the researchers perhaps underestimating their chances of getting SRC support. It is to be hoped that this situation will improve rapidly, the submission of more high-quality grant applications being the necessary first step.The SKC Chemistry Committee have in the past given their major support to analytical chemistry via Advanced Course Studentships for MSc courses. In 1979 27 out of the Committee’s 67 Studentships were so allocated, a figure that excludes the Courses in Chemical Spectroscopy and Forensic Science at East Anglia and Strathclyde Universities, respec- tively. At least eight analytical MSc courses are currently SRC-recognised, and a number of others (some admitting only part-time students) operate successfully a t both universities and polytechnics. It is evident that the SRC still feels this to be an important means of supporting the subject; the Analytical Sciences Panel has set up a Working Party currently reviewing MSc courses.The importance of these courses is indeed unquestionable for, with the relative neglect of analytical chemistry as a subject a t undergraduate level, the MSc courses are playing a vital role in maintaining a supply of trained analysts. This view is supported by the high percentage of MSc graduates who proceed directly to jobs in industry and the public services; others, who go on to a PhD degree, also move to industrial jobs thereafter, having received an invaluable part taught course, part research training combination. It is an interesting thought that, in the very long term, the growth of undergraduate courses in analytical sciences may reduce the demand for MSc courses, which, at present, often fill an obvious gap in the training of chemists at BSc level. Meanwhile, however, the increasing support and interest of the SRC in the MSc courses as well as in research is invaluable and much to be welcomed. Lastly, what of the large number of analysts who qualified some years ago but are being left behind by the rapid development of their subject ? Not the least encouraging sentence of the SRC panel’s report was that in which the need for intensive short courses was identified. At present such courses (quite a number are are already in operation) are often the results of purely voluntary and extra work by members of analytical chemistry groups in universities and polytechnics; if no direct financial support of the courses is possible, SRC support for the other activities of these groups may at least provide indirect encouragement. J. N. MILLER

ISSN:0144-557X    

DOI:10.1039/AP9801700457

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

458 THE “CONFERRING CHEMIST” Anal. Proc. The ”Conferring Chemist“ Comments and Comparisons on SAC 80 In the words of Francis Bacon, “Reading maketh a full man Conference a readye man and writing an exacte man.” Certainly in scientific activity, “conference” and conferences play a vital part in the gathering, surveying and dissemination of theory, information and methodology, the review of novel ideas and developments and the provision of opportunity for direct interaction between scientists, teachers, and students. Some believe that time spent in “conference” detracts from the “real” business a t hand, but nevertheless scientific meetings are increasingly prevalent and their proceedings ever more frequently appear in printed form, thus developing, it is hoped, Bacon’s “exacte man.” As an affirmed “analytical conferee” on both sides of the Atlantic, I was asked to combine some impressions of SAC 80 with more general thoughts and comparisons between styles andNovember, 1980 THE “CONFERRING CHEMIST” 459 approaches to conferring in the USA and the UK.The following assessment is the outcome of this assignment. Perhaps one of the more noteworthy observa- tions on SAC 80 concerned the marked lack of attendees from North America; sadly, the complete shift in economics over the past few years has made it very hard for analytical chemists (academics at least) to attend Euro- pean meetings. This is in most marked con- trast to the situation at earlier SAC and similar conferences where strong transatlantic con- tingents made major contributions. To the detriment of over-all scientific discipline, the Atlantic now forms a bigger barrier, in both directions, than in times past.For academic analytical chemists, US government grants seldom provide for overseas travel ; further, some agencies, such as the National Science Foundation, now have a policy to support travel only to certain (few) specified overseas meetings; it is my impression that analytical meetings have seldom attained this limited support. I believe that SAC 80 was a particularly fine conference, which regrettably suffered from lack of US participation; in my mind it exemplified some of the very best features of conferences generally as well as fully living up to the reputation of SAC conferences over the years, both scientifically and socially. I do not mean to suggest in any way that North American analytical chemists lack “conference.” In fact, the range of meetings is exceptionally wide and it was considered that some information on these might be of interest to members of the RSC Analytical Division.The great number of meetings of widely differing styles certainly provides for all tastes, although none perhaps parallels the SAC series. The Analytical Division of the American Chemical Society fills a very similar position to that of the RSC, notably in that it is the second largest subject division in membership. There are two National ACS meetings each year typically attended by 8 000-10 000 people, held in major city centres; their location is sometimes most attractive, as exemplified by recent meetings in New Orleans, Honolulu and Las Vegas (incidentally, the last location was an alternative defined only 4 weeks before the August 1980 meeting, made necessary by a hotel strike in San Francisco-the relocation of such an enterprise at such short notice was impressive indeed).The Analytical Division regularly provides an extensive 4-5-day pro- gramme of symposia and general papers in three or four parallel sessions. Usually more than 200 papers are presented; the Division has yet to implement poster sessions, although other ACS Divisions have done so with success. Prominent special symposia include those for the Fisher Award in analytical chemistry and the Supelco Award in chromatography, both sponsored by industrial companies. The ACS Analytical Division sponsors each year a Summer Symposium.This is a 3-day special-topic symposium held at different college campus locations ; recent topics have included Enzymes in Analytical Chemistry, Chromato- graphy and Ancillary Techniques and Correla- tion Techniques and Optimisation Methods in Analysis. Attendance a t these symposia is around 150-200 and in some respects they have similar features to the SAC series. The ACS Analytical Division also co-sponsors other meetings ; these include the FACSS (Federation of Analytical Chemistry and Spectroscopy Societies) meeting, now in its seventh year. Co-sponsors for this meeting, which covers all aspects of analytical chemistry, are the Society of Applied Spectroscopy, the Association of Official Analytical Chemists and the Analysis Instru- mentation Division of the Instrument Society of America.A major instrument exhibition is also a part of this meeting. A somewhat similar meeting is the Eastern Analytical Symposium, held annually in New York city. A newer entry into the field of combined symposia and exhibitions is the Expochem series, based in Houston, which has developed in part from a series of international chromato- graphy symposia. All of these meetings feature special-topic symposia with invited speakers and also include courses and workshops, which are usually well attended. The largest analytical chemistry meeting is the annual Pittsburgh Conference, now in its 32nd year. Although no longer held in Pitts- burgh (its most recent location has been Atlantic City), it is still largely organised by scientists from that city.As well as attracting over 800 papers and latterly over 15 000 attendees, this meeting is the primary “Instru- ment Show” in the USA, currently attracting some 500 exhibiting companies. These typi- cally introduce new products a t the Pittsburgh meeting both by means of the exhibition and also through papers presented. At this meeting the latter tend to predominate over fundamental research presentations. In complete contrast to these instrumenta- tion-orientated meetings and exhibitions are the Gordon Research Conferences. From June to August each year some 8-10 different con-460 THE “CONFERRING CHEMIST” Anal. PYOC. ferences are held each week a t schools and colleges in New Hampshire, the sessions attracting government, industrial and academic scientists to talk on a wide range of chemically related ideas including analytical chemical topics.The information exchanged in these informal, relaxed and secluded summer sessions is very much a t the “cutting edge” of experi- mentation and may in fact be years away from formal publication. These conferences were initiated in 1931 and every year over a 100 conferences are attended by more than 17 000 scientists ; many conferences are heavily over- subscribed, but the organisers make great efforts to accept a mixture of the eminent and the inexperienced in the groups. Another strong feature of US analytical chemical life is the existence of a number of flourishing special-interest societies, including the Society of Applied Spectroscopy, the Electrochemical Society, the Microchemical Society and the North American Thermal Analysis Society. All have active conference and local section activities.Also prominent are discussion group meetings, operating mainly in areas of high concentration of chemical activity ; many chromatography groups in particular are well attended and feature eminent speakers. Even academic analytical chemists have devised their own yearly series of con- ferences, such as the Mid-West Universities Analytical Chemistry Conference (MUACC) and the North East Universities Analytical Chem- istry Conference (NEACC), where sessions are held on both teaching and research activities. It is certainly clear that the analytical chemistry profession in the USA does not lack opportunity to “confer,” but the very features which distinguish many of these meetings often reduces their usefulness because of sheer size and the resulting anonymity.Often their location in major city centres detracts from any real social value for the meetings; they tend to be purely 9 a.m.-5 p.m. events. Also, the pressure upon academics to present is very strong and may sometimes lead to inferior presentations on occasion ; similarly, industrial chemists often find it impossible to justify attendance unless a paper is presented. The plethora of US conferences also lack some other strong features of meetings such as SAC 80. The truly international atmosphere typical of SAC meetings is mostly lacking. Sadly, the US scientist often considers little outside the North American boundaries, either in con- ference or in literature searching.The con- tinuing atmosphere of camaraderie as old friends meet again and new friends are made is usually largely absent from US meetings. Programmes usually leave little time for personal inter- actions (Gordon Conferences are notable ex- ceptions) and the social programme is usually minimal in this regard. The US has something to learn here, I believe, particularly where an exceptional conference such as SAC 80 at Lancaster is concerned. And so to the outstanding memories of SAC 80. The opening Plenary Lecture by Professor Whitehead on “Assessing the Analytical Quality of the Clinical Laboratory” made many salient points in an area often regarded with some concern by many analytical chemists.This lecture followed an opening ceremony of a much more positive character than had been the case for SAC 7 7 . Professor Malmstadt’s progno- sis of the 80s as regards the trends in analytical instrumentation proved most challenging ; he preserved his reputation to be thought- provoking and in addition his remarks a t the Conference banquet served to place in a good perspective the aspirations of the individual scientist in relation to wider issues and morali- ties. Dr. Greenfield delivered an excellent overview of one of the most rapidly growing of present analytical techniques, plasma emission spectroscopy. This is an area where a studied appraisal by one who was instrumental in the foundation of the field acts as a worthwhile antidote to the extensive claims and counter- claims of instrument designers and manu- facturers. Professor Baiulescu also raised thought-provoking issues on the changes in analytical philosophy and implementation aris- ing with the replacement of old techniques by new, not always entirely for the better. My personal recollections of SAC 80 are entirely pleasant: the unique occasion of an “international”-level piano recital by John Ogden held in a truly mayoral setting after a magnificent example of civic hospitality ; a conference banquet of a high standard both as regards menu and with respect to speeches ; even the opportunity afforded by a very wet train ride on the Ravenglass and Eskdale Railway to discuss extensive comparisons of American and Australian university life. Alto- gether a memorable conference. SAC 83 surely cannot arrive soon enough ! PETER C. UDEN Univevsity of Massachusetts, Amherst, Mass., USA

ISSN:0144-557X    

DOI:10.1039/AP9801700458

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

November, 1980 Report of Meeting REPORT OF MEETING 461 North West Region Summer Meeting, Aberystwyth, June 27-29,1980 A salient feature of the activities of the North West Region is the holding of the summer meet- ing, usually in some less than accessible spot with a reputation for superb scenery. This year it was held in the College of Librar- ianship, a t Tanybwlch, Aberystwyth. This was a charming old house, close to the sea shore. It had floors on split levels, and given the fire pre- cautions, a host of doors. The maze-like organisation of the rooms and corridors could well have inspired the game “Cluedo”- fortunately the weekend passed without fatali- ties. On the Saturday morning a visit was made to the Welsh Plant Breeding Station, where Professor J. P. Cooper described efforts that were being made to develop new strains of plants, e.g., drought resistant plants.The weather had improved markedly, and the visit was made in bright sunshine. In the afternoon the members heard three talks: “The Work of the Plant Breeding Station,” by Professor J. P. Cooper; “Silver and Lead Mining in Mid-Wales,” by Xlr. I>. L. Harvey; and “A Talk on Welsh- built Sailing Ships,” by Professor Bowen, Department of Geography, Aberystwytli. The talks were equally interesting and gave much information on Welsh history and culture. A barrage of questions followed and the meeting concluded a t 6.00 p.m. Later in the evening came the Banquet, which gave our hosts the chance to display their culinary skills, which they did to such good effect that we are nominating them for an Egon Ronay Award.Following the meal we had an hour’s enter- tainment by a male singing group (15 strong) with songs in Welsh and English, and the jokes in English for those who had not the tongue. The Sunday also acknowledged the presence of the North Western Analysts with blue skies and sunshine. The party travelled next to the CEGB Hydroelectric Power Station at Rheidol, which not unnaturally boasted the lowest cost per unit of electricity produced in the whole of the CEGB (even cheaper than nuclear). Furthermore, it has improved the environment, reducing flooding, and has provided trout fisheries. Maurice Cropper, the Station Manager, gave us a fascinating talk on the intricacies of the scheme. It was then but a short trip to the Llywernog Silver - Lead Mine near Ponterwyd, where once galena had been mined and smelted. The mine represents a major element of the industrial legacy of Mid-Wales. It has been partly restored, and affords a daunting impression of the rigours of a miner’s life.Interesting too, were the Cornish names associated with these mines. We were again grateful to Mr. Harvey for letting us see this decayed monument, now well preserved, to a byegone way of life. We returned to Tanybwlch for an excellent lunch, where the Chairman formally thanked our hosts, not least the lady chef, for pampering us during our brief stay. Now homeward bound to our Northern parishes we stopped off at the centre for Alterna- tive Technology a t Machynlleth. There, we saw the ways in which future man, starved of fossil fuels, would not only survive but prosper. The Chairman seemed fascinated in the possi- bilities of pedalled vehicles ! The run home through the superb Welsh scenery, in perfect weather, was a fitting climax to this very fine weekend. We were all (35 adults) grateful for the efforts of our Secretary, Gerry Davison, who had organised this enterprise, and kept it within sensible financial bounds. A novel feature of the meeting was the ability of parents t o bring young children to the weekend’s activities. This did not cause any problems and enabled members to participate who otherwise would have been prevented from doing so. G. B. CRUMP

ISSN:0144-557X    

DOI:10.1039/AP9801700461

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

462 PROFESSOR G. F. KIRKBRIGHT Anal. Proc. ANALYTICAL SCIENCES MONOGRAPH No. 5 Dithizone by H. M. N. H. Irving The author of this volume has gathered together a body of historical and technical data that will be of interest to many practising analytical chemists. Brief contents The Properties of Dithizone; Metal- Dithizone Complexes and Their Formulae; The Photo- chemistry of Metal Dithizonates; The Extrac- tion of Metal Dithizonates; The Less Familiar D i th izone Com plexes ; Organometal lic D ith i - zonates; Practical Considerations; Some Add it iona I Applications of D it h izone ; Some Unresolved Problems; Bibliography. Clothbound 112pp 8%’’ x 55” 0 85186 787 1 f7.25 (RSC Members f5.50) THE ROYAL SOCIETY OF CHEMISTRY, Distribution Centre, Blackhorse Road, Letchworth, Herts., SG6 1 HN Professor G.F. Kirkbright Dr. Gordon Frank Kirkbright has been appointed to the new Chair in Analytical Sciences at the University of Manchester Institute of Science and Technology. He is to be the first Head of the newly created Depart- ment of Instrumentation and Analytical Science. It is anticipated that this major academic development, with three professorial staff and the appropriate ancillary teaching and techni- cal staff, will enable a response to the new industrial revolution and the challenging needs of industry in terms of research and education. Kirkbright, who has since 1977 been Reader in Analytical Chemistry and Head of a large research group a t Imperial College, undertook his first degree and postgraduate research in analytical chemistry a t the University of Birmingham, where he graduated with a PhD in 1962. After postdoctoral research in the USA at the height of the “Brain-drain” he was induced to return to Europe via a DSIR (now SRC) /NATO Fellowship.This Fellowship was first spent a t the Technische Hochschule, Vienna, and then in the Department of Chemistry a t Imperial College. Subsequently, Dr. Kirkbright joined the staff at Imperial College, in 1964, and progressed to the position of Reader in Analytical Atomic Spectroscopy, researching particularly into fluorescence spectroscopy, atomic-absorption spectroscopy and the development of novel atom cells. He was awarded the degree of DSc by the University of London in 1971 and the first Silver Medal of the Society for Analytical Chemistry in 1974 for contributions to atomic and molecular spectroscopy.He leads a large, active research group concerned with the development of novel spectroscopic techniques of analysis, a t present specialising in radiofrequency plasma emission spectroscopy for environmental and clinical trace analysis and optoacoustic spectro- scopy for the direct examination of solid and liquid materials. These activities, and expan- sion into other areas, are expected to continue a t UMIST. In addition to academic duties, he retains an active interest in the affairs of EDT Research, of which he is a founder Director and Company Chairman. Professor Kirkbright has been active in the work of a number of National and International Agencies and Committees concerned with Analytical Science. He is a t present a member of the Council of the Royal Society of Chemistry Analytical Division and past Chairman of the Atomic Spectroscopy Group of the Division.November, 1980 THOMAS CLARK, PROFESSOR OF CHEMISTRY 1833-1860 463 He is currently serving as an Associate Member formation of the new Department a t UMIST of Commission V(II1) of the IUPAC and is a will lead to the establishment of an over-all member of the International Atomic Energy concept of instrumentation and analytical Agency Advisory Group on Trace Elements in science and teaching of and research into the Biological Materials. It is expected that the subject as an integrated discipline.

ISSN:0144-557X    

DOI:10.1039/AP9801700462

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

November, 1980 THOMAS CLARK, PROFESSOR OF CHEMISTRY 1833-1860 463 ”Hot-Blast“ Clark: Thomas Clark, Professor of Chemistry, Marischal College, 1833-1860 Thomas Clark, one of the original members of the Chemical Society, was born in Ayr on March 31st, 1801. His father was captain of a merchant ship and his mother originated Ayrshire needlework. Clark was a dull boy at school until he was about 13 and began mathe- matics, whereafter he blossomed and became an outstanding pupil. He was a great schemer and became known as “Philosopher Tom.” At the age of 15 he entered the counting-house of Charles Macintosh and Co., the inventors of waterproof cloth. The firm’s main activity was the manufacture of cudbear, a scarlet dye used in making military uniform cloth, but alum was also extensively made.Clark training in the counting-house diagrammatic representation of often said his helped him in scientific facts, but he was not a good accountant, and on dis- covering where his true talents lay the Macin- toshes recommended a shift to chemistry. He thereupon obtained a job as chemist a t Tennant’s Chemical Works in St. Kollox. Only 10 years after his leaving school (and without qualifica- tions) he was appointed Lecturer in Chemistry at the Glasgow Mechanics’ Institute. From what is known of his lecture programme, he appears to have been in advance of his time in the interpretation of chemical theory, and t o have understood the role of hydrogen in the properties of acids, teaching the navy and Dulong hypothesis that all salts or acids are combinations of metals or hydrogen with other elements, a view that was not generally accepted until Liebig’s investigation on organic acids in 1838.He also seems to have conceived the notion of structure in chemical compounds. In 1826 he published his papers on sodium pyro- phosphate’l sodium arsenate2 and a new sodium ph~sphate,~ the first of these constituting a landmark in the development of the theory of isomerism and the emerging ideas on poly- atomicity. Only a year later, with the intention of teach- ing chemistry in a medical school and not of entering general practice, he entered the Uni- versity of Glasgow as a medical student and took his degree in 1831. In the meantime, he became apothecary to Glasgow Infirmary in 1829 and published three papers on pharmaceutical t o p i ~ s .~ - ~ In 1832 he published a review on three articles on the system of weights and measures, and in 1853 two review articles on the law of patents.’* He had collected material for an article “On the lost history of English weights and measures,” but as it was never completed, the history remains lost. He seems to have had a tendency to collect material but not publish it. In 1833 the Chair of Chemistry a t Marischal College (Aberdeen’s second university-then 240 years old, a t a time when the whole of * The obituary in J . Chem. SOC., 1868, 21, viii is incorrect in saying that the last two articles were unpublished. Bain (Professor of Logic, Aberdeen) , who wrote the obituary, corrected it later in his biography of Clark.464 THOMAS CLARK, PROFESSOR OF CHEMISTRY 1833-1860 Anal.Proc. England had only just acquired its third) be- came vacant on the death of Professor French. The advertisement of the vacancy (Fig. 1) makes interesting reading, especially the last sentence in view of traditional Aberdeen thrift- ness.* Clark applied, but immediately ran into problems associated with the clause “Candidates are required to have received a regular Acadeni- ical education,” it being held that an MD did not meet the requirement (the other two candidates both held Aberdeen arts and medical degrees). After a protracted debate a vote of Senatus was taken. Of the nine present, four voted for, four against and one abstained. The Principal used his casting vote to accept Clark’s applica- tion. The candidates were then given an oral and a written examination and required to give a short trial lecture on a subject chosen by the exawinevs, “either with or without the use of notes, as each candidate may prefer,” though candidates were allowed the use of books to prepare the lecture.Clark came out best and was duly appointed. The cost was A31.19.8, consisting of L20 to one of the external examin- ers (but nothing to the other!), ,tllO.S.lO for dinner in college for the candidates, examiners, the Principal and the professors (expense account band-wagons are nothing new!) and i1.13.10 for the advertisement. students all the doubts and difficulties associated with the topics taught, which did not go down well with a student body that lived by the opinion “Is it a fact or not a fact? If it’s not a fact, what are you teaching it for?.” His course suffered from long digressions that were not concerned with chemistry, and his own dis- coveries were always given prominence.Per- haps he gave as much as he was paid for, his total salary being A73 p.a. until 1839, plus much less than L200 from fees, out of which he had to buy the apparatus and employ a qualified assistant. He was of a strongly practical turn of mind, which inclined him more to the discovery and application of facts than to theorising. It was this bent that led to some of his most notable work. Before his appointment to the Chair of Chemistry he had acted as adviser to a Stafford- shire chemical company, and when Nielson, the discoverer and patentee of the hot-blast process, was involved in a patent case, Clark was asked to support his cause.In 1834 he read a paper to the British Association on the theory of the hot-blast process,s and it was interest in this technique that gained him the nickname of “Hot-Blast” among the students at Marischal College. In 1839 he read another paper to the British PROFESSORSHIP OF CHEMISTRY The Professorship of Chemistry in the Marischal College and University, Aberdeen, being vacant, Candidates for the office are required to transmit testi- monials of character and education to the Principal of the College, on or before the 5th October next-and to attend at Marischal College, on the 10th October next, at 10 o’clock a.m., in order to be examined as to their knowledge of Chemistry, both in Theory and Practice, in presence of the Principal and Professors, the Patrons of the office.By the Deed of Foundation of this Professorship, Candidates are required to have received a regular Academical education; and any relation of the late Mrs. Blackwell of Pilmuir, must be preferred, if equally qualified with others. Particulars, as to the duties and emoluments of the office, may be learned by applying to the Secretary of Marischal College. Testimonials and letters of inquiry must be postpaid. Fig. 1. Advertisement, 1833. As a lecturer, Clark had strong peculiarities. Taking nothing on trust, he laid before his Association, on atomic weight determination,’ and in 1840 described his method for detecting trace amounts of arsenic by the reaction of * Moreover, under the terms of the foundation, the arsine with silver nitrate solution,lO almost Professor was to be paid L40 p.a.out of the income, 40 years before ~ ~ t ~ ~ i t j ~ ~i~ most after certain other payments had been made, but only if the income allowed it. Any shortfall meant important work* was concerned with a reduced salary! his water-softening process, patented in 1841,November, 1980 THOMAS CLARK, PROFESSOR OF CHEMISTRY 1833-1860 465 and his soap test for the hardness of water. The “chemical friends,” giving the details. The soap test was described in the patent specifica- circular was reprinted in the Chemical Gazeitell tion and did not receive wider circulation until (Fig. 2) and is an interesting example of his style 1847, when he sent a private circular to his of writing.It appears that he completely over- On the Examination of Water for Towns, for its Hardness, and for the Incrustation it Deposits on Boiling. By Professor CLARK. AT various times during the last few years, I have been applied to for information respecting methods I had adopted for examining waters for towns; but ill health has almost always prevented me from returning a satisfactory answer. There has been recently somewhat more occasion for such inquiries, in consequence of the Commissioners of Woods and Forests having been pleased to require, as one of the indispensable conditions to a bill for supplying water to a town being presented by them to Parliament, that there shall be given, in reference to the waters already supplied to the town, as well as in reference to the waters proposed to be supplied- A statement of the quality of the water as exhibited by chemical analysis, specifying its adaptation for domestic and manufacturing purposes, and its degree of hardness with reference to the tests and scale of Dr.Clark. I take the liberty to write out one answer to all inquiries; and, imperfect as I am aware the information must be, I hope my friends will receive it with such indulgence as is due to an effort at affording information to others by a person confined to bed by illness and unfit for any considerable exertion of mind. The processes alluded to for the examination of waters are two-one for ascertaining the hardness of water, one for ascertaining the alkalinity. Each of these processes is fully described in the specification of a patent printed in the Number of the ‘Repertory of Patent Inventions’ for October 1841 .. . . Referring to the specification, I begin by describing a few improvements that have been suggested by experience since the specification was enrolled. Process for Ascertaining the Hardness of Water In June 1843, having occasionally before met with some few specimens of waters, and more especially soft waters from springs, where the indications of the soap-test, which in general are remarkably distinct, were obscure, I discovered the cause of this obscurity to be an excess of carbonic acid, that is, an excess over and above what is necessary to form alkaline or earthy bicarbonates. This excess has the property of slowly decomposing a lather once formed.For the purpose of guarding against an excess of carbonic acid in all cases, I recommend that, before you measure out the water for trial, you shake it briskly in a stoppered glass bottle half-filled with it, sucking out the air from the bottle at intervals by means of a glass tube, so as to change the atmosphere in the bottle. In all trials of waters above 16” hardness, not only should such waters, and the distilled water to be used along with them in the trials, be treated in this manner, previous to their being measured out and mixed, but the measured mixtures themselves should be treated in like manner, before any soap-test is added to them. The soap-test itself should be occasion- ally so treated before it is measured out. To obtain uniform results with the soap-test, I recommend that as soon as you observe that a lather is formed, such as will remain all over the surface of the water for five minutes, you take a note, but only an interim one, of the quantity of the soap-test that has been added.In about half an hour you should shake the bottle again, to see whether the lather will still remain for five minutes. If the water under trial do not exceed 4” or 5” of hardness, it is likely to require a little more soap-test upon this renewed shaking; but in every case where more soap-test is required, let more be added to the water. This latter quantity and the former will together make up the whole soap-test that is to determine the hardness of the water under trial. For hours afterwards, unless perhaps the water do not exceed 1” or 2” of hardness, a lather lasting for five minutes may be restored by your shaking the phial, This mode of procedure, by producing a lather whose permanence we may repeatedly verify, will conduce much to the uniformity and accuracy of our trials.Fig. 2. From the “circular,” reprinted in Chemical Gazette, 1847.11466 THOMAS CLARK, PROFESSOR OF CHEMISTRY 1833-1860 Anal. Proc. looked the effect of magnesium in the soap test, which was pointed out later by Campbell,l2 and the discrepancy between soap-test hardness and the hardness calculated from alkalinity, etc., was an embarrassment to Clark. An ardent politician with liberal views, Clark entered freely into debate and polemic with characteristic verbosity. In 1837 he vigorously supported the union of Aberdeen’s two universi- ties for purposes of administration but strongly urged the retention of the two separate Faculties of Arts, each with its own professors.This was true foresight, since when the amalgamation took place in 1860, with union of the Chairs as well, it was James Clerk Maxwell who was dis- missed from his post of Professor of Natural Philosophy a t Marischal College! He also con- sidered that all professors should be appointed by competitive examination, saying that the only objections he had heard were from “parties whose expectations were founded mainly on other grounds than qualifications for the office.” After the disruption of the Church of Scotland in 1843, Clark was prominent in the movement to abolish the religious tests imposed on professors before admission to their Chairs.It was a t about this time that Clark began to show the effects of the brain disease that was to plague him for the rest of his life and led to his being unable to teach again, and although he contin- ued to serve Marischal College as best he could, his strength was never again equal to unbroken work. Eventually the amalgamation of the two universities in 1860 led to his being super- annuated. He had married in 1849, and was later deeply sorrowed by the early death of his only child, a gifted boy. Clark died rather suddenly in 1867, being unable to get up in the morning and being dead by 2 o’clock. A strong personality, with loves and hates on the grand scale, he was generally amiable, certainly generous and sympathetic, and beloved by his intimates.His love of detail and the highest standards of accuracy caused him ever to be seeking to refine his work, to the point that he did not know when i t would be sensible to stop. As a result, much of his work never reached publication. The saddest comments on Clark’s career are surely the remark by Thomas Graham (“Clark narrowly escaped being a great man”) and the statement in the obituary notice in Chemical News : “Though not a Fellow of the Royal Society, Dr. Clark, had he lived, probably would have been made one at the next election, since his friends were circulat- ing a certificate for signatures.”l3 Clark’s interests ranged far beyond chemistry, and included linguistics, the reform of English spelling, English style and grammar and the historical origin of the Gospels.It seems likely that it was this very breadth of interest that militated against his achieving his full potential, and that had he published more and fussed less he would indeed have received the full recogni- tion his merits deserved. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. References Clark, T., Edinburgh J . Sci., 1827, 7, 298. Clark, T., Edinburgh J . Sci., 1827, 7, 309. Clark, T., Edinburgh J . Sci., 1827, 7, 311. Clark, T., Glasgow Med. J., 1830, 3, 293. Clark, T., Glasgow Med. J . , 1830, 3, 372. Clark, T., Glasgow Med. J.. 1831, 4, 109. Clark, T., Westminstev Rev., 1832,16, 37; 1835, 22, 172, 447 (unsigned articles). Trans. Roy. SOC. Edin., 1836, 13, 373. Clark, T., B r i t . Assoc. Advan. Sci. Rept., 1839, Clark, T., B r i t . Assoc. Advan. Sci. Rept., 1840, Clark, T., Chem. Gazette, 1847, 5, 100. Campbell, D., Phil. Mag., Ser. 3, 1850, 37, 171. Chem. News, 1867, 16, 292. Part 2, 43. Part 2, 83. ROBERT A, CHALMERS Notice to Subscribers Subscription rates for I981 (with indexes) Analytical Proceedings alone: f30.00 (UK/Eire) ; $70.50 (USA) ; f31.50 (Rest of world) Analytical Proceedings with The Analyst and Analytical Abstracts: f 1 90.00 (U K/Eire) ; $471.50 (USA) : f200.50 (Rest of world) Subscriptions should be sent to : The Royal Society of Chemistry, Distribution Centre, Blackhorse Road, Letchworth, Herts., SG6 1 HN, England

ISSN:0144-557X    

DOI:10.1039/AP9801700463

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

Nozlember, 1980 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION 467 ANNUAL CHEMICAL CONGRESS The Annual Chemical Congress of The Chemical Society and The Royal Institute of Chemistry was held at Durham University from April 9th to l l t h , 1980. A Symposium on Modern Techniques for Surface C haracterisation was organised by the Analytical Division. Modern Techniques for Surface Characterisation The following are summaries of eight of the papers presented a t the Annual Chemical Congress on April 9th to l l t h , 1980. Surface Analysis in Metallurgical Phenomena E. D. Hondros and C. T. H. Stoddart National Physical Laboratory, Teddington, Middlesex, T W11 OL W In recent years there has been an awakened recognition that some properties of metals and also certain metallurgical processes are determined by the fine-scale chemical composition of interfaces, such as grain or phase boundaries, as well as free surfaces.ly2 These constitute localised zones with differing microchemistry resulting from the re-partition and concentration of alloying or impurity species by solid-state equilibrium or kinetic processes.The advent of surface analysis techniques enabling the chemical composition of such surfaces and inter- faces to be determined has stimulated interest in this aspect of metallurgy and the techniques are being employed increasingly and successfully in advancing understanding of the pheno- mena and in solving practical problems. The three major techniques used in metallurgy, Auger electron spectroscopy, X-ray photoelectron spectroscopy and secondary ion mass spectroscopy, are described3 with examples of their application. Auger Electron Spectroscopy (AES) In this technique3-5 the surface to be analysed, which must be in a clean vacuum, is irradiated with an electron beam, typically 2.5-5.0 keV, and an energy analysis is performed on the emitted secondary electrons.The Auger electrons, produced by a radiationless transfer of energy within the atom, have energies characteristic of the emitting atoms and a characteristic line spectrum is obtained (Fig. 1). The Auger electrons have energies in the range 0-1500 eV, with mean free paths in the solid equivalent to a few atomic layers, so that only those electrons originating from the outermost atomic layers are analysed and information on the elements present at the surface is obtained with a sensitivity of 0.1% of a monatomic layer. An important feature of AES for metallurgical applications, where microstructure is of prime importance, is that the electron probe can be focused and rastered to give a display of the elemental distribution on the surface.When combined with argon ion-beam sputtering to remove atom layers from the surface material, an elemental depth and spatial composition matrix can be constructed with a resolution of about 1 pm in the plane of the surface and 1 nm in depth from the surface. The composition of internal inter- faces such as grain boundaries and interphase boundaries is obtained by fracturing the material in an ultra-high vacuum in the spectrometer and analysing the resulting fracture surfaces. The power of AES in solving practical problems in metallurgy is illustrated by the following examples.Boron Inhibition of Oxidation of Fe - 10% Cr Alloy The dramatic effect of trace amounts of boron in the vapour phase in inhibiting oxidation of Fe - 10% Cr alloy at 600 "C6 was finally shown by AES to be due to a concentration of the boron in the surface 10-20 nm layer only and not at the oxide - metal interfa~e.~ The boron concentration at the air - oxide interface was associated with an enrichment of chromium and supported a mechanism in which networks of -0-B-0- covalent bonds in the oxide prevent the ingress of oxygen into the oxide film, thereby retaining a coherent film and468 MODERN TECHNIQUES FOR SURFACE CHARXCTERISATION Anal.Proc. allowing chromium to diffuse for a much longer time and to build up a protective layer at the free surface. 1 i- I- Fe I I I I--- - Fe 0 200 400 GOO Electron energy/e\/ 800 1000 Fig. 1. Auger electron spectra from (a) cleavage facet and (b) grain boundary on fracture surface of a 2.25 Cr - 1 Mo steel failed by impact a t low tempzrature in ultra-high vacuum.l0 Lubricating Role of Lead in Free-machining Alloys Although free-machining steels and brasses containing small amounts of lead have been used extensively in manufacturing industry for many years, the way in which the lead increases tool life has been a continuing subject of debate. AES analysis of the swarf s ~ r f a c e s ~ ~ ~ has shown that these are covered with a single atomic lead layer, probably produced by extrusion processes during cutting.I t appears that this remarkably thin layer is sufficient lubricant to reduce direct contact between the rake face of the tool and the swarf, thus minimising adhesive wear. Effect of Phosphorus Grain Boundary Segregation on Stress Corrosion Cracking of a Low-alloy Steel The combination of surface sensitivity and spatial resolution of AES is particularly useful for the analysis of microcrystalline fracture surfaces, yielding valuable information on the composition of internal interfaces. Fig. 1 compares the composition of a cleavage facet with a grain boundary in a 2.25Cr - 1Mo steel with a grain size of 20-30 pm, and segregation of phosphorus impurity to grain boundaries is evident .lo The intergranular stress corrosion properties in hot nitrate solution are affected by less than 5% of a monatomic layer of phosphorus segregating to the grain boundary and deteriorate with increasing phosphorus level up to about 20% of a monolayer, probably because the phosphorus enhances dissolution of the grain boundary.Higher phosphorus levels have no further effect as the crack propa- gation rate is then probably limited by the removal of debris from the crack tip. AdditionNovember, 1980 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION 469 of lanthanum to precipitate the phosphorus as phosphide can prevent its segregation to grain boundaries, producing a marked improvement in stress corrosion properties. Adhesion of the Metal - Ceramic Interface The composition of the interface formed between solidified sessile drops of a range of iron alloys on sapphire was determined by AES after removal of the drop from its substrate in a shear test.ll Fe-Cr alloy formed a strong bond to the sapphire, and this was correlated with a sharp segregation of chromium in the first 10 nm of the alloy surface which had con- tacted the alumina and which may be associated with formation of a chromium-rich oxide interlayer.Nickel counteracted the effects of chromium, presumably by lowering the bulk chromium activity . X-ray Photoelectron Spectroscopy (XPS or ESCA) Surface analysis by this technique3J2 is similar to AES but is effected by irradiating the sample with an X-ray beam, e g . , A1 Ka, 1486.6 eV photon energy, and by measuring the energies and intensities of both the emitted Auger electrons and photoelectrons. From the energy of the X-ray photon and the kinetic energy of the emitted photoelectron the binding energy of the electron can be calculated, and this is characteristic of the atom species.The binding energies are sensitive to the chemical environment of the atom and shifts in these energies give information on the nature of surface chemical compounds, for example oxidation state. It is this capability which has made the technique particularly attractive to chemists and materials scientists with problems relating to catalysis, polymers and adhesion and to metallurgists in the study of oxidation and corrosion. The main disadvantage of the technique is that it uses a broad X-ray probe and the spatial resolution is limited to about 1 mm, but when used in conjunction with AES this disadvantage can be overcome to some extent.The following examples illustrate the use of XPS in metallurgical applications. Protective Films on Aluminium Brass Condenser Tubes XPS has revealed the complex interface chemistry in the thin protective oxide layers formed on an aluminium brass condenser tube in which the cooling sea water was dosed with iron( 11) sulphate to inhibit pitting c0rrosion.1~ These layers contained mainly copper(1) and iron(II1) ions, but on areas of the tube where the layers were non-adherent and non- protective they were shown to consist of a duplex structure in which the iron deposits were separated from the underlying brass by a layer rich in zinc and magnesium with copper in the copper(I1) state but containing no iron.Surface Composition of Rolled and Heat-treated Steel Sheet XPS analysis showed. the efficiency of degreasing treatments in removing rolling oils from the steel ~ h e e t . ~ ~ ~ ~ An alkaline orthosilicate solution also formed a very thin (5 nm) film on the steel surface consisting mainly of Si02.nH20 containing calcium from the industrial water used. An interaction between this silica film and the steel substrate occurred during subsequent annealing, resulting in segregation and oxidation of manganese, chromium and phosphorus at the free surface or in grain boundaries. Graphite formation on the external surface due to carbon diffusion was suppressed by the presence of the silica film and a suitable surface for bright tinning obtained.Secondary Ion Mass Spectroscopy (SIMS) In SIMS3,l5-l8 the sample surface is bombarded with argon or oxygen ions ( e g . , 5 keV energy) and the emitted secondary ions are mass analysed. When used in the static mode with a defocused beam and very low primary ion beam current densities15-17 (10-l1 A mm-z), the technique analyses the outermost atomic layers with the following advantages : surface structure and the nature of chemical compounds present may be deduced from the masses of the ejected ionised clusters of atoms; detection of hydrogen and its compounds is possible (hydrogen is not detected by AES or XPS); and the sensitivity is extremely high (10-6 monatomic layer) for a number of elements. These features are now being used to give new470 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION Anal.Proc. information on adsorbed gas species, including hydrogen and water vapour, on metals and of the primary processes of oxidation. Composition profiles are obtained by using the technique in the dynamic mode1* by increasing the primary ion beam current density, e.g., to lO-'A mm-2 by focusing the beam to 250 pm and rastering over a 1 x 1 mm area to improve sputtering uniformity. In the ion microprobe version of SIMS18 the beam is further focused to 1 pm diameter with a 10 pA beam current and an image of the surface in a particular component is obtained by scanning the beam, but the technique then averages over several atomic layers in depth. The extremely high sensitivity of SIMS is used extensively in the semiconductor industry to determine dopant profiles in silicon and in the metallurgical field for bulk analysis of additives and impurities.Two examples illustrate the use of SIMS in the analysis of surfaces and interfaces in metallurgical systems. Oxidation Inhibition in Nickel-based Turbine Alloys A profile through the oxide layer (0.25 pm thick) formed at 1000 "C in air on a nickel- based turbine alloy Ni - Cr - A1 - y,y'-Cr,C, eutectic doped with 0.5% m/m of yttrium as an inhibitor showed that it was enriched in aluminium and chromium oxides but depleted in nickel oxide (Fig. 2).19 Yttrium was present throughout the layer but with a maximum concentration at the oxide - alloy interface. The segregation of yttrium at this interface can be related to its role in improving the adhesion of the oxide scale.20 The detection of an A1-0-Cr+ ion indicates strong bonding between aluminium and chromium oxides in the scale. The C2- ion profile shows the absence of the carbide inclusions from the scale. 0 100 300 500 700 900 Depth etchedhm Fig.2. Composition - depth profile, obtained by SIMS, of of oxide layer formed 'at 1000 "C in air on Ni-Cr-A1 - y,y'- Cr,C, eutectic doped with yttrium.ls Hydrogen Embrittlement in Welded Steels An important question in welding metallurgy concerns the role of hydrogen in initiating cold cracks. Secondary ion microscopy of polished sections of welds21 showed directly that hydrogen collected at carbide or manganese-based sulphide inclusions, particularly near martensitic regions in the heat-aff ected zone of steel welded with rutile electrodes.Hydrogen atoms, originating in the electrode material, are thought to diffuse to the inclusion - matrix interface where they form molecular hydrogen, thereby weakening the interface, causing decohesion and initiating cracks. Other Surface Techniques Applied in Metallurgy The analysis of internal surfaces, such as grain boundaries and matrix - inclusion inter- The use of AES, XPS faces, with high resolution is of primary importance in metallurgy.November, 1980 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION 47 1 and SIMS generally requires fracture to expose the internal interface for analysis, but if the particular interface is strong then this presents a major practical difficulty. Techniques being developed which circumvent this difficulty and analyse the intact interface are briefly mentioned. Field ion microscopy with the atom probe22 and field desorption microscopy23 analyse a specimen tip with atomic spatial resolution and are potentially capable of mapping out the structure and chemical details of the adsorption of solutes to internal interfaces.Transmission electron microscopy with energy a n a l y s i ~ ~ ~ s ~ ~ has a spatial resolution of about 10 nm, adequate for coarser non-equilibrium segregation and for precipitate microanalysis. Recent developments in scanning transmission electron microscopy using a field-emission gun allow single atom imaging in principle26 and combined with electron energy-loss spectro- scopy27J* provide analysis with an estimated spatial resolution of a few atom diameters.In ion back-scattering ~pectroscopy~~ the analysis is averaged over a depth of about 25 nm from the surface and, unlike AES, XPS and SIMS, this technique can therefore be used for analysis of grain boundaries of samples fractured in air, provided the segregants are heavier than the matrix atoms and are not likely to be confused by atmospheric contamination. Conclusion The features of three major surface spectroscopies, AES, XPS and SIMS, have been described with examples of their application and are seen to be complementary, They offer a powerful combination for the solution of metallurgical and materials problems where the microchemistry of the free surface and internal interfaces is involved. The authors thank Drs.C. Lea, M. McLean and M. P. Seah of the National Physical Labora- tory for helpful discussions. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 1 1 . 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. References Hondros, E. D., and Seah, M. P., Int. Metall. Rev., 1977, No. 222, 262-301. Proceedings of the Conference on Residuals, Additives and Materials Properties, Philos. Trans. Czanderna, A. W., Editor, “Methods of Surface Analysis,” Volume 1 of “Methods and Phenomena: Gallon, T. E., and Matthew, J. A. D., Rev. Phys. Technol., 1972, 3, 31. Rivikre, J. C., Contemp. Phys., 1972, 14, 513. Hendy P., Kent, B., Lloyd, G. O., Roades-Brown, J. E., and Saunders, S. R. J., “Eurocor 77,” Lea, C., Met. Sci., 1979, 13, 301. Stoddart, C. T. H., Seah, M.P., McLean, M., and Mills, B., Nature (London), 1975, 253, 187. Stoddart, C. T. H., Lea, C., Dench, W. A.. Green, P., and Pettit, H. R., Met. Techn., 1979, 6, 176. Lea, C., Met. Sci., 1980, 14, 107. Hondros, E. D., Philos. Trans. R . Soc. Lond., Ser. A , 1980, 292, 21. Briggs, D., Editor, “Handbook of X-ray and Ultraviolet Photoelectron Spectroscopy,” Heyden, Castle, J. E., Epler, D. C., and Peplow, D. B., Covros. Sci., 1976, 16, 145. Leroy, V., Richelmi, ‘J., and Graas, H., Metall. Rep. CRM, 1976, No. 49, 49. Benninghoven, A., Surf. Sci., 1973, 35, 427. Benninghoven, A., Surf. Sci., 1975, 53, 596. Barber, M., and Vickerman, J. C.. Surf. Defect Prop. Solids, 1976, 5, 16:; Werner, H. W., in Fiermans, L., Vennik, J., and Dekeyser, W., Editors, R . SOC. Lond., Ser.A , 1980, 292, 1-341. Their Applications in Science and Technology,” Elsevier, Amsterdam, 1975. Society of Chemical Industry, London, 1977, p. 105. London, 1977. Electron and Ion Spectro- scopy of Solids,” NATO Advanced Study Institute Series B32, Plenum, New York, 1978, pp. 324- 441. Stoddart, C. T. H., and Hunt, C. P., Philos. Trans. R. SOC. Lond., Ser. A , 1980, 292, 134. Bullock, E., Lea, C., and McLean, M., Met. Sci., 1979, 13, 373. Sotkovszki, P., Larsson, S., and Easterling, K. E., Met. Sci., 1979, 13, 597. Miiller, E. W., and Tsong, T. T., Prog. Surf. Sci., 1973, 4, 1. Southon, M. J., Boyes, E. D., Turner, P. J., and Waugh, A. R., Surf. Sci., 1975, 53, 554. Edington, J. W., and Hibbert, G., J . Microsc., 1973, 99, 125. Leapman, R. D., Sanderson, S. J.. and Whelan, M.J., Met. Sci., 1978, 12, 215. Crewe, A. V., Q. Rev. Biophys., 1970, 3. 137. Brown, L. M., Inst. Phys. Conf. Ser, 1977, No. 36, 141. Donald, A. M., and Craven, A. J., Philos. Mag., 1979, A39, 1. Guttmann, M., Krahe, P. R., Abel, F., Amsel, G., Bruneaux, M., and Cohen, C., Metall. Trans.. 1974, 5, 167.472 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION Anal. Proc. Low Energy Ion Scattering as a Tool for Surface Structure and Corn posi t i o n An a I ysis D. G. Armour Department of Electrical Engineering, University of Salford, Salford, M5 4 WT The analytical capabilities of low energy ion beams have now been exploited in techniques in which secondary ions and electrons, scattered ions and neutrals and p h ~ t o n s l - ~ are detected. Ion scattering using primary rare gas ions in the energy range between a few hundred electron volts and a few kiloelectronvolts has proved to be particularly interesting from the point of view of surface analysis, as the form of the scattered ion-energy distributions is determined almost entirely by the composition and structure of the outermost atomic layer.Ion scatter- ing spectroscopy (ISS) is thus based on the energy analysis and detection of particles scattered through a specified angle during impingement of a mass analysed, mono-energetic and highly collimated beam of ions on to the target surface. The technique owes its surface specificity to the use of electrostatic energy analysers, which allow only particles scattered in the ionised state to be detected and the selection of low energy, rare gas ions at the probe.The large scattering cross-sections associated with low energy particles combined with the highly efficient neutralisation of high ionisation potential rare gases via the Auger process4 lead to an almost complete suppression of the ionised particle yield from scattering events occurring below the outermost surface layer. Efficient neutralisation also occurs, of course, for those particles scattered from the surface layer itself and consequently it is generally necessary to employ high probe ion fluences, typically 1014-1016 ions cm-2 per energy spectrum. This can lead to significant target perturba- tion and establishment of a straightforward quantitative relationship between measured ion yields and surface concentrations of target atoms contributing to the scattering is precluded by the generally unknown neutralisation probabilities.It is interesting to note that although the high fluence requirements and neutralisation probability problems may be overcome, either by using time of flight analysis to allow detection of both ionised and neutral particles or by employing alkali ions as the primary particles, such that very high ion yields are obtained, these techniques lack the inherent surface specificity of the less sensitive ion scattering arrangement. Despite its quantitative limitations, which cannot in all instances be overcome by calibration using standard targets, and uncertainties concerning the influence of such phenomena as thermal lattice vibrations and inelastic energy loss processes on the measured energy distribu- tions, low energy ion scattering is finding increasing application in the study of areas such as gas adsorption, thin film deposition and surface damage creation and annealing during ion irradiation where structural and compositional changes occurring in only the outermost atomic layer need to be monitored.The capabilities of the technique and the ways in which it has been developed for different types of analysis depend strongly on the fundamental atomic collision processes taking place at the surface and it is these processes, together with examples of their role in analysis applications, that form the subject of this paper. , Theoretical Basis and Practical Capabilities of Low Energy Ion Scattering as a Surface Analytical Technique The basis of low energy ion scattering as a means of determining the elemental composition of solid surfaces is the relationship between the energy of the scattered ion and the mass of the target atom.For an ion reflected in a single, elastic binary collision with a surface atom, this relationship is derived using simple energy and momentum conservation laws and the final energy of the projectile particle does not depend on the nature of the inter-atomic forces involved. For an ion of mass M I and energy E, scattered through an angle 8 in a collision with a target atom of mass M2, the final, or retained, energy is given by c o d & (A2 - sin2O)f . . - * (1) . . 1 - . [ (1 + A ) E, = E, ___ where A = M2/M1. Only the positive sign applies when A is greater than 1.For compara-November, 1980 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION 473 tively large scattering angles, the single binary collision model has been found to describe the scattering behaviour very accurately and, for the often used 8 value of go", conversion of the measured energy scale into a mass scale is particularly simple because the above equation simplifies to . . .. A - 1 Having established a simple working relationship between the peak energy and the mass of the scattering centre it is obviously necessary, from a compositional analysis point of view, to consider such factors as sensitivity, resolution and surface specificity. Sensitivity is of major interest from two points of view in that it is important to determine the extent to which the ion yield at a particular energy gives an absolute measure of the number of atoms per unit area of a particular species present in the surface and to define minimum detectable amounts.For an atom species i with surface concentration Ni, the detected ion current is given by the equation da . df2 ri = i0 N~ A 2 ALIT,P, where lo is the incident current, A the bombarded area, AQ the acceptance solid angle of the detector, Ti the transmission factor of the analyser and detector, dui/df2 the differential scattering cross-section into unit solid angle and Pi the probability of being scattered as an ion. As neither the differential scattering cross-section nor the probability of being scattered as an ion is known accurately the quantitative limitations of the technique are immediately apparent.However, it has been found for a number of different target-projectile systems that Pi does not depend to a significant extent on the chemical environment of the particular target atom and, in general, reliable qualitative measurements that can be compared with, and in some instances calibrated against, the results of other techniques such as neutron activation analysis5 can be carried out. As none of the other techniques possess the single layer depth resolution of ISS, calibration is not straightforward unless sub-monolayer coverages are involved. Although the minimum detectable amounts depend very much on the particular experimental system considered, e.g., through factors such as lo, AQ and Ti, as well as primary species and energy, typical figures for systems having reasonable mass resolution are 3 x monolayers (ML) for bromine on silicon using helium ions,6 3 x ML for oxygen on nickel using neon ions7 and 5 x lo-* ML for gold on silicon using helium ions.5 I t is interesting to note that for an experimental system with a given energy resolution, the mass resolution is optimised by the use of heavy primary particles and large scattering angle and that compli- ance with these conditions tends to minimise the scattering cross-section and hence reduces the sensitivity.In addition to the single binary elastic scattering, which is ideally suited to composition analysis but which gives no structural information, theoretical and experimental studies have shown that for a wide range of scattering conditions the collision with one surface atom is affected by the presence of neighbouring atoms.This involvement of a number of surface atoms forrns the basis of the use of ion scattering for surface structure analysis as the screening effects, which lead to the shadowing of one atomic species by another or to the development of specific collision sequences such as the quasi-single and quasi-double collisions predicted using chain the0ry,8,~ are strongly dependent on the arrangement of the surface atoms. In practice, two techniques, binary scattering - shadowing and multiple scattering, have been developed for obtaining information concerning the relative positions of the surface atoms using ion scatter- ing. The basic principles of the shadowing technique are to vary the scattering geometry, angle of incidence or target azimuth, usually with a constant scattering angle in order to determine the circumstances under which atoms of one species are located within regions masked by atoms of another.The analysis is simplified by using light primary ions and large scattering angles such that multiple scattering, beam induced damage and shadowing effects on the outward trajectory are minimised. Under these conditions, the masking is essentially a straightforward geometrical effect and qualitative information about the surface atomic arrangements, for example, whether or not the surface is reconstructed or whether adsorbed atoms take up sites in or on top of the surface, can be obtained. Quantification of the measure-474 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION Anal.Proc. ments is, however, more complicated as it involves consideration of atomic screening func- tions and thermal lattice vibrations that affect the extent to which masking occurs. The major application of this technique has been in the study of adsorption and for oxygen on (1 10) silverlo and (100) nickelll surfaces the positions occupied by the oxygen atoms have been quan- tified to within & 1.0 and In contrast to the binary scattering - shadowing technique, the multiple scattering method employs experimental conditions that are designed to maximise multiple scattering effects and heavy primary ions, usually neon or argon, small total scattering angles and specular reflection geometries are selected.The technique is based on the dependence of the multiple scattering processes on the inter-atomic spacings in the surface atomic rows and the procedure is to measure the scattered ion-energy distributions for different target azimuths. The nature of the quasi-single (QS) and quasi-double (QD) collision sequences and the dependence of their contributions to the energy distributions in inter-atomic spacings are illustrated in Fig. 1. The major features of interest are the energy of the QS peak and the relative heights of the peaks, and in a study of oxygen adsorption onto a (110) nickel surface the appearance of a new QS peak in the spectra obtained for scattering along the <i10> surface direction has been interpreted as being caused by a reconstruction of the surface during the early stages of ad- sorption.The position of this peak indicates a doubling of the original atomic spacing in this direction .I2913 0.2 A, respectively. 6keVAr++Ni(11O)8=3Oo ~)=15" T=250°C Fig. 1. Dependence of multiple scattering processes on interatomic distances. The ability of ion scattering to yield both compositional and this form of structural informa- tion concerning the outermost layer of a solid simultaneously makes it an attractive surface analysis technique and its use, particularly in conjunction with low energy electron diffraction and Auger electron spectroscopy, offers considerable potential in many areas where an under- standing of surface processes is required. References 1. 2. 3. 4. Thomas, G.E., Swf. Sci., 1979, 90, 381. Smith, D. P., Bull. Am. Phys. SOC., 1966, 11, 770. Smith, D. P., J . Appl. Phys., 1967, 38, 340. Hagstrum, H. D., Phys. Rev., 1954, 96, 336.November, 1980 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION 475 5. 6. 7. 8. 9. 10. 11. 12. 13. Ball, D. J., Buck, T. M., MacMair, D., and Wheatly, G. H., Swf. Sci., 1972, 30, 69. Brongersma, H. H., and Mull, P. M., S w f . Sci., 1973, 35, 355. Armour, D. G., Van den Berg, J. A., and Verheij, L. K., J . Radional. Chem., 1979, 48, 359. Mashkova, E. S., Molchanov, V. A., Parilis, E. S., and Turaev, N. Yu., Phys. Lett., 1979, 18, 7. Parilis, E. S., and Turaev, N. Yu., Sou. Phys. Dokl., 1965, 10, 212. Heiland, W., Iberl, F., Taglauer, E., and Menzil, D., S w f . Sci., 1975, 53, 383. Brongersma, H.H., and Theeten, J. B., Surf. Sci., 1976, 54, 519. Verheij, L. K., Van den Berg, J. A., and Armour, D. G., Surf. Scz., 1979, 84, 408. Van den Berg, J. A., Verheij, L. K., and Armour, D. G., Surf. Sci.. 1980, 91, 218. High Energy Ion Scattering for Surface and Interface Studies D. W. Palmer School of Mathematical and Physical Sciences, University of Sussex, Brighton, BN1 9QH This paper reviews the principles, and outlines applications, of the use of the back-scattering of protons and helium ions of energies about 50 keV to a few MeV, for the elemental composition analysis of solid surfaces, for depth profiling of composition through thin layers and interfaces and for surface structure studies. The information is obtained using the energy spectrum of the elastically back-scattered ions, together with measurements of incident energy and angular dependences for the structure studies.The conventional geometry for composition analysis by ion scattering is shown in the inset of Fig. 1, The proton or helium ion beam is produced by a positive ion accelerator (e.g., of the Van de Graaff type) and strikes the solid sample held in a vacuum chamber. Ions scattered at a well defined backward angle are received by a silicon surface-barrier detector, which, together with an appropriate pre-amplifier, amplifier and multi-channel pulse-height analyser , allows the energy spectrum of the back-scattered ions to be measured. The principle of the elemental composition analysis is that the ratio of scattered to pre-scattered ion energy depends on the ratio of the masses of the scattering atom and the ion, heavier scattering elements giving larger scattering energies (approaching the pre-scattered energy).For protons of about 1 MeV and for 4He+ ions of about 2 MeV, the scattering follows the classical Rutherford law, and the scattering intensity is then proportional to the square of the atomic number 2, of the scattering element. A 2 MeV 4He+ ion beam is very often employed to give optimum discrimination between elements in the sample. I on beam Sample Heavy impurities on surface - Matrix Light impurity atoms Non- -Scattering from matrix atoms . Channelled Energies of observed scattered ions __+ Fig. 1, Surface composition analysis. Surf ace Composition Analysis Fig. 1 shows the kind of back-scattered ion energy spectrum obtained when heavy and light mpurities are present in a very thin layer on the sample surface. On a medium mass substrate476 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION Anal.Proc. the sensitivities can be as good as about low2 monolayer for a heavy element such as gold, and about 1 monolayer for a light element such as oxygen. For a single-crystal sample the surface stoicheiometry of the matrix atoms can be quantitatively measured by making use of the ion- channelling effect; when the ions are incident parallel to a low index axis of the sample the scattering from the bulk atoms is very much reduced leaving scattering from the surface atoms as a peak or peaks on the back-scattering spectrum (Fig. 1 ) . Depth Profiling of Composition1 The protons and helium ions gradually lose energy as they travel through the sample, coming to rest only after distances of about one to several microns.Ions that are back-scattered at a depth x therefore reach the detector with an energy dependent on x because of the energy losses for the ingoing and outgoing paths. Thus, for each element (or, strictly, each isotope) in the sample the energy axis of the back-scattered spectrum can become a depth scale. If then we know what elements are present we can determine their concentrations as functions of depth into the sample. Fig. 2 illustrates how this method can be used to measure the inter-diffusion of two elements across the interface between them (e.g., gold as element B and aluminium as element A2); the formation in the solid phase of particular compounds can be deduced from the experimental, post-heat-treatment spectrum by taking into account the 2: dependence of the scattering intensities.In other studies, segregation of impurities to interfaces has been detected by peaks formed on the energy spectrum. 0 Energies of observed scattered ions + Fig. 2 . Depth profiling of composition: interdiffusion near surface. Solid line, before heat treatment; and broken line, after heat treatment. Surface Structure Analysis The principle of the use of ion back-scattering for the measurement of transverse and perpendicular relaxations of surface atoms is shown in Fig. 3. It relies upon the fact that the exit of ions scattered from the bulk is blocked along certain directions by rows of atoms and that the exit of ions scattered by the second outermost layer is blocked along slightly different directions by the individual outermost atoms.The bulk and near-surface scattering yields are distinguished by means of their different ion energies. At the present time the method allows a relaxation of about 0.5% of the bulk inter-layer spacing to be detected. Nickel3 and platinum* have recently been studied in this way. This is an important surface-study tech- nique, which seems to have greater sensitivity and ease of analysis for surface-atom location measurements than the well established low energy electron diffraction method. Conclusion Ion elastic scattering (IES) is a powerful and developing tool for investigation of solid surfaces and interfaces.November, 1980 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION 477 I Ion .\ Directions of I beam$& scattering minima Surfacer Bulk ’/ ’/ Re’axation f 0 0 0 0 0 0 .,Po of su dace 0 0 0 0 0 of’.0 0 0 0 0 . / d o 0 0 0 0 0 ./a 0 0 0 0 ./U 0 . 0 0 . 0 0,“ 0 0 0 0 0 0 ./a 0 0 0 0 0 0 0 , d o 0 0 0 0 0 0 0 Fig. 3. Surface structure analysis. References 1. 2. 3. 4. Poate, J. M., Tu, K. N., and Mayer, J. W., Editors, “Thin Films: Interdiffusion and Reactions,” John Campisano, S. U., Foti, G., Rimini, E., Lau, S. S., and Mayer, J . W., Phil. Mag., 1975, 31, 903. Van der Veen, J. F., Tromp, R. M., Smeenk, R. G., and Saris, F. W., Surf. Sci., 1979, 82, 468. Davies, J. A,, Jackson, D. P., Matsunami, N., and Norton, P. R., Surf. Sci., 1978, 78, 274. Wiley, New York, 1975.Surface Characterisation of Cold-rolled Steel Sheets V. Leroy Centre de Recherches Metallurgiques, A bbaye d u Val-Benogt, B-4000 Liege, Belgium Because the sheet surface plays an important role in the subsequent use of the bulk material, the surface properties of cold-rolled steel sheets are of great importance. This paper is intended to give a general survey of the work performed at CRM in the field of surface analysis; it deals with problems related to the surface chemistry of two important products: the black-plate, which is the base material for electro-tinning, and the cold-rolled sheets for cold forming. In the cold processing of steel strip, the free surface of the sheet comes into close contact with many different materials that could affect the composition of the external layers.I t can be assumed that the surface chemistry of the final product depends on the contribution of each stage in the cold processing line. For this reason, and because such contamination cannot be simulated on the laboratory scale, all of the specimens must be removed from industrial lines. For black-plate, specimens were taken from different stages of industrial lines : after descaling, cold-rolling, electrodegreasing, batch annealing or continuous annealing and temper-rolling. For the samples examined after descaling in hydrochloric acid (with the addition of corrosion inhibitor) and before coating in pickling oil, Auger spectroscopy revealed chlorine and calcium contamination. Such pollution may lead to spot rusting on temper- rolled steel sheet.The presence of these residues depends strongly on the rinsing treatment after pickling; the immersion and spraying methods result in some differences. Sulphur and nitrogen were also detected; their presence is due to the inhibitor in the pickling bath, which may be an alkylthiourea. One observes also a distinct enrichment of copper, nickel and arsenic on the descaled surface, the extent of which is closely related to the bulk copper content of the material. The copper enrichment is induced during hot rolling and coiling of the steel strip. As copper, in contrast to iron, cannot be oxidised in the prevailing atmosphere, it accumulates below the oxide film and some of it diffuses back into the metallic matrix. After descaling in the presence of the inhibitor it appears on the free surface.Copper or nickel may also be present on the surface as an electroplated film by an exchange mechanism between metallic iron and some ions present in the pickling solutions.478 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION Anal. Proc. This paper considers also the problem of degreasing in orthosilicate solution and shows that this treatment results in the formation of a silica film 0.2 nm thick on the degreased product. In the degreasing bath, hydrolysis of orthosilicate gives some silicic acid (H,SiO,), which is soluble at pH 12. During rinsing, the pH decreases to 7 and the orthosilicic acid does not remain in solution; consequently, gelation of the orthosilicic acid results in the formation of a silica film on the free surface in which calcium ions are trapped.The main purpose of this silica film is to prevent sticking between the turns of the coil during batch annealing; we see later that such a film has important effects in relation to other problems, such as graphite formation on the free surface during batch annealing. The batch annealing treatment a t 660 "C in a protective atmosphere of nitrogen containing 5% of hydrogen induces interactions between the silica film and the steel substrate, which produce a thicker external layer. At the same time, manganese, phosphorus and chromium segregate strongly at the free surface, where they are present as oxides and form a homo- geneous film. The manganese content in the external layer may be as high as about 10%.Because of the short annealing time in the continuous process, the film left after degreasing does not interact with the steel substrate. Experience has shown that the surface chemistry as described here for the as-annealed conditions is adequate for tinning. Problems may occur, however, in some specific instances during the batch annealing treatment; the most serious is the formation of graphite on the free surface of batch-annealed steel strip, which can be demonstrated by, X-ray diffraction. Because of the degreasing treatment that precedes annealing, this graphite formation cannot be due to carbon contamination from residual rolling oil; instead, it is ascribed to cementite destabilisation and carbon migration from the bulk to the external surface during heat treatment.It has been shown that graphite formation can be inhibited by adjusting the steel compo- sition so as to counteract cementite destabilisation at high temperature ; the carbide-forming elements manganese and chromium are particularly effective in this respect. Residual elements such as copper and nickel, which can form stable sulphides on the free surface, also reduce graphite formation. It should be recalled that such residual elements may be enriched in the external layers during the heating step of the annealing cycle. Addition of sulphur-containing compounds in the degreasing solution or in the rinsing solution also appears to be effective in inhibiting graphite formation during batch annealing. With steel sheet for forming, steel strips are not usually cleaned before coiling and batch annealing.Consequently, the cleanliness of the sheets depends on many parameters, such as the nature and the drag-out of pickling and rolling oils, the contamination of rolling solutions with tramp oils or metal fines, the extent to which the oils distil at high temperature, the coiling force and the annealing cycle. Both steel producers and users now recognise the detrimental effect of carbonaceous residues on steel surfaces on the basis of the salt spray test performance of phosphatised and painted parts. This carbon contamination can be measured by the test proposed by the Ford laboratory. Surface carbon and other elements can be analysed semi-quantitatively by X-ray photo- electron spectroscopic (XPS) analysis on an area of 5 mm2 with a depth resolution of 0.5 nm.Such an analysis shows that the surface chemistry is complex. One observes on the free surface: (a) a carbon peak corresponding to C-C bonds, which increases in intensity with total contamination; ( b ) oxygen is detected as two separate peaks corresponding to a thermal oxide (02-) and a hydroxide; the intensity of the 02- peak decreases as the total contamina- tion increases; and (c) manganese is enriched on the free surface in the form of an oxide. Contamination by chlorine or calcium due to the pickling bath or to the hardness of the water used in the different stages of the cold processing line was also observed. Zinc, phosphorus and lead were also detected in some instances, indicating the presence of tramp oil in the emulsion or of extreme pressure additives. With XPS we observed a strong carbon peak with contributions from different carbon bonds.More precisely, the depth profiles showed that the position and shape of the carbon peak change with depth below the free surface. We think that such observations may be useful for studying the mechanism responsible for hydrocarbon elimination during annealing.November, 1980 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION 479 In conclusion, it is evident that the surface chemistry of industrial products is very com- plex. It is encouraging to observe that the use of new surface analytical techniques such as secondary ion probe analysis, Auger electron spectroscopy and XPS has resulted in a new view of the surfaces of industrial products.The Analysis of Annealed Electrotinned Steel T. J. Crichton, J. P. G. Farr," Miss J. Russon and M. Saremi Mrs. J. Pountney and A. J. Bentley and L. G. Earwaker Department of Industrial Metallurgy. University of Birmingham, P.O. Box 363, Birmingham, B 15 2TT Department of Physical Metallurgy, University of Birmingham, P.O. Box 363, Birmingham, B15 2TT Radiation Centre, University of Birmingham, P.O. Box 363, Birmingham, B15 2TT Typically, commercial tinplate consists of steel electroplated with tin to a thickness of the order of 1-2 pm. The electrodeposit is flash-flowed, resulting in a composite depth profile with a thin (about 0.1 pm) inter-metallic layer sandwiched between the substrate steel and free tin at the surface. In various industrial processes tinplate is subjected to thermal treat- ments and it is necessary to know their effects on the composition of the surface layers.The value of surface analysis is enhanced when a number of techniques can be brought to bear on a problem ; in this study Auger electron spectroscopy (AES), Rutherford back-scattering (RBS) and anodic electrolytic stripping (ES) were used in conjunction with a metallographic examination by scanning electron microscopy (SEM) and with some conventional chemical analyses (by atomic absorptiometry), Experimental and Results Samples of tinplate were annealed at temperatures from 100 to 600 "C for periods from 1 min to 4 h. Metallograp hy Even using the SEM a taper section (6') was required to reveal the inter-metallic layer under the free tin surface of specimens annealed at low temperature.At medium temperatures this layer grew, to a maximum thickness at 300 "C, above which (350 "C) it limited and then (400 "C) diminished. Electron probe analysis for tin to iron proportions gave some evidence for the formation of inter-metallics other than FeSn, but the alloy layer showed inhomo- geneity that prevented definitive analyses. Electrochemical Stripping The galvano- static stripping graph shows a series of arrests: A, at -1.06 V (versus Hg - HgO) corresponds to the dissolution (partially chemical, i.e., non-Faradaic) of tin; B, at -840 mV; C at -400 mV (the main inter-metallic dissolution step); and D at +650 mV where oxygen is evolved on a passive iron surface). Step B is comparable in length (seconds) with Step C for specimens annealed at less than 300 "C but is much smaller for those annealed above this temperature.Between step C and step D other events are manifest on specimens annealed at 350 and 400 "C. It was concluded from a comparison of ES with metallography that step B also corresponded to an alloy stripping plateau, i.e., that the total inter-metallic content was given by B Both free tin and iron - tin inter-metallics dissolve anodically in hot alkali. plus c. Auger Spectroscopy 14n attempt to use scanning Auger spectroscopy in combination with a cratering technique to provide sections through the electroplate, made by Dr J. M. Walls (Loughborough Con- * To whom all correspondence should be addressed.480 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION Anal.Proc. sultants Ltd.) was unsuccessful, due to smearing of the tin. Auger analyses were therefore made conventionally, using a fixed beam and 500 V Arf surface erosion. Full profiles have not been obtained because the surface layer thicknesses were not suitable; the most revealing analysis was on plate partially stripped to the B plateau. Here, the iron and tin peaks were approximately equivalent but the strongest peak was due to oxygen, undiminished after removing 300 atomic layer equivalents of FeSn,. This may have mechanistic significance. A small lead peak was found (see below) but removed after sputtering 100 atom layers, and a small persistent calcium peak may relate to other report^.^.^ Rutherford Back-scattering RBS was carried out using 2 MeV alpha particles from a Dynamitron and a detector with a resolution of 15 keV. Decoration of the surface with lead at the stripping plateau B was first revealed by RBS, for which the technique is particularly f a v o ~ r a b l e .~ ? ~ Because the incident radiation is adequately penetrative for the surface layers5 it was hoped that RBS would reveal the distribution of tin and iron in depth, especially as the respective atomic numbers are ap- propriate. Computer simulation was required, there are many parameters to adjust5 and the program used6s7 was first demonstrated to describe accurately such model systems as gold and silver films evaporated on to aluminium foil. Qualitatively RBS results are consistent with metallography and electron probe analyses.The effect of annealing below 232 "C on the tin distribution is small; there is a marked change after annealing at greater than 232 "C consistent with progressive alloying and depletion in free tin. After anneals at 500 "C the spectra are consistent with diffusion of tin from the inter- metallic layer into the steel substrate. Difficulties in performing quantitative simulations were experienced after anneals in the temperature range 300-400 "C where it seems likely that the inter-metallic layer contains additional compounds to FeSn,. Further experiments are in progress. Chemical Analyses Tin analyses (by atomic absorptiometry) for annealed and for anodically stripped specimens indicated that some loss of tin through oxidation occurred in 200 min at 500 "C but the major- ity of the remaining tin had diffused into the steel.The chemical analyses showed clearly that the onset of tin solution occurs at 350 "C, and that this process dominates during annealing at higher temperatures. Discussion From a consideration of all the analytical evidence gained the effects of annealing tinplate, Below the during manufacture and subsequently, result in the depth profile shown in Fig. 1. 600 500 100 o.2 0 i 0 - 0 50 100 150 200 250 Heat treatment time/min Fig. 1. Alloy growth curves a t elevated temperatures.November, 1980 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION 481 melting point of tin, Tm, alloy (Le., inter-metallic) growth follows a roughly parabolic law; between T , and 300 “C alloy growth graphs are still approximately parabolic, growth rates have increased sharply but we have insufficient graphs to derive a dependable activation energy.Above 300 “C growth is initially parabolic but after some time the alloy thickness diminishes as a result of migration of tin from the alloy layer into the iron substrate, where it is held in alpha-solid solution. Above 500 “C this process becomes very rapid, so that the inter- metallic growth stage was almost unobservable on the heat treatment time scale of the present investigation. This pattern of behaviour is significant for a number of industrial process that involve the thermal handling of tinplate. The system provides interest for the surface analyst insofar as analytical methods involving sectioning or erosion of the surface layers carry the risk of preparative artefacts. RBS is there- fore advantageous and the comparison of computer-simulated RBS with experiment and with results from the other techniques is encouraging.Further RBS on partially anodically stripped alloy (300-500 “C) specimens is in hand. A danger of this technique (also of Auger spectros- copy without a finely focused incident beam) is that results may be misleading if the surface layers are not well stratified or if the strata are not homogeneous in composition. Higher instrumental resolution is therefore desirable, with some metallographic (SEM) checks. References 1. 2. 3. 4. 5. 0. 7 . Kunze, C. T., and Willey, A. R., J . Electrochem. Soc., 1952, 99, 354. Leroy, V., Anal. Proc., 1980, 17, 477. Habraken, L., Shungu, T.D., and Leroy, V., L e Vide, les Conches M i m e s , 1979, 199, 385. Mackintosh, W. D., in Kane, P. F., and Larrabee, G. B., Editors, “Characterisation of Solid Surfaces,” Ziegler, J . F., Editor, “New Uses of Ion Accelerators,” Plenum Press, New York, 1975. Morris, J ., U.K.A.E.R.E., R.B.S. Simulation Code. Earwaker, L., Birmingham Radiation Centre Report BRC-79/03 (1980). Plenum Press, New York, 1974, p. 403. Some Applications of ESCA to Industrial Problems R. Holm Department of Applied Physics, Bayer A G , 0-5090 Leverkusen, Federal Republic of Germany Many effects can be used to obtain information on the surfaces of solids, but with the present state of the art ESCA (Electron Spectroscopy for Chemical Analysis) is the leading surface analysis technique for the study of chemical problems, because it is in general non- destructive, it is normally free from charging problems in measurements on insulators, it permits the most reliable detection of compounds and it permits the most reliable quantita- tive measurements.Photoelectrons and Auger electrons with a kinetic energy characteristic of the emitting elements and their binding states are observed. These applica- tions are still important, especially for the detection of polar structures, e.g., in mesoionic compounds. The opportunities for characterisation of compounds (chemical shifts, multiplet and satellite structures) have been studied extensively for nearly all elements in the Periodic Table2 and are a reliable basis for the detection of compounds in surface analysis.In comparison with other surface analysis techniques, the quantitative evaluation of ESCA spectra is rather easy. The intensity of each ESCA line reflects the number of emitting atoms in a particular binding state. Relative sensitivity factors for the individual elements have been publi~hed.~ The surface sensitivity of ESCA is given by the escape depth of the photo and Auger electrons. Thus, the sampling depth is less than 10nm.4 This provides opportunities for monolayer analysis and the obtaining of non-destructive in-depth information about layers down to a depth of approximately 10nm.5-6 If information is to be obtained from even lower depths, surface layers have to be removed, e.g., by sputtering. The sample is irradiated with X-ray photons (e.g., A1 Ka, 1486 eV).ESCA started as a method for the determination of molecular structure.l I t is most important that there are almost no matrix effects.482 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION Anal. Proc. The energies used in ion bombardment (500 eV-5 keV) are several orders of magnitude greater than the binding energies of the molecules and therefore sufficient to break chemical bonds and form new ones. Where organic compounds are concerned such ion-induced reactions are particularly easy to observe because in this instance there is no restoration of the initial state through annealing processes. It can also be assumed, however, that it is no longer possible to identify inorganic compounds reliably in areas opened up by ion bombardment .' The spatial resolution is normally limited to a few millimetres.The sensitivity is generally limited to about 0.1% of a monolayer. There are instances where ESCA is unable to characterise compounds adequately and others where the information depth is too great. In these instances other surface analysis techniques should be applied in combination with ESCA in order to obtain the optimum results. Despite these many points in favour of ESCA, the method also has disadvantages. Examples of Application In the chemical industry, surface analysis is relevant mainly to corrosion, wear, catalysis and polymer technology. Corrosion and Wear In connection with these phenomena it is frequently desirable to study the surface layers that are formed on metals and alloys subjected to mechanical, thermal and chemical exposure, as the information obtained in this way can facilitate the choice of materials for chemical plant or reveal the causes of actual damage.For such purposes ESCA permits the qualita- tive and quantitative analysis of the surface layer (including the determination of the oxidation states of the elements detected), enables the thickness of the surface layer to be measured non-destructively and enables the metal layer beneath it to be analysed in as far as it is within the escape depth range of the photo and Auger electrons. ESCA investigations reveal the behaviour of the alloying components in the metal surface and provide indications as to the mechanism by which the corrosion products leave the surface. The examples discussed concerned stainless steels,s Co - Cr - Mo alloys as used for metal implants in orthopaedi~s,~ brass,lO Ag - Sn alloys6 and Cu - Sn alloys.Catalysis Throughout the world technical catalysts are chosen and optimised according to largely empirical techniques. As surface analysis procedures are only possible under a vacuum, the surface analyst is confronted by the problem that direct analysis during the course of a catalytic reaction is generally impossible. There is therefore no alternative to the investiga- tion of catalysts before and after defined phases of a formation or reaction. A special airlock system is therefore used to ensure that the catalyst samples are transferred from the reactor to the analytical instrument without coming into contact with air. In a particular instance one must decide whether it is preferable to retain the reaction temperature during the transfer procedure or to freeze certain states.ESCA serves to determine the oxidation of the nickel (valency, mean layer thickness) and the amount of residual aluminium (as hydroxide) on the surfaces of the particles. Much routine work in catalysis is done by identifying poisons and the valence state of the active metal components. More complex systems are supported metal catalysts, in which discrete metal particles are dispersed over the surface of an inert material. The metal signal intensity will depend on the particle diameter and the escape depth of the photo and Auger electrons. The production and ageing of Raney nickel was discussed.6 High Polymers High polymers are encountered in many forms, e.g., as fibres, foams, engineering plastics and coatings.The problems that can be investigated by the methods of surface analysis are correspondingly diverse. They include not merely such typical surface changes as the effects of etching, weathering and corona discharge, but also the contamination of polymerNovember, 1980 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION 483 surfaces and the detection of migration by such polymer additives as lubricants, antioxidants and antistatic agents, the identification of which is important because they may prevent bonding, printing or other treatments. Interface problems also arise where there is contact between polymers and pigments, fillers, glass fibres or metals. Examples of polymer-metal bonds are found in galvanised plastics, radial tyres, cable insulations and capacitor film.A review of these applications will be given elsewhere.ll The routine use of surface analysis methods in the chemical industry is still in its infancy. The examples published so far have demonstrated, however, that real surfaces and, if suitable preparation techniques are used, interfaces too can be characterised. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11 References Siegbahn, K., Nordling, C., Fahlman, A., Nordberg, R., Hamrin, K., Hedman, J., Johansson, G., Bergmark, T., Karlsson, S.-E., Lindgren, J., and Lindberg, B., “ESCA: Atomic, Molecular and Solid-state Structures Studies by Means of Electron Spectroscopy,” Almquist and Wiksells, Uppsala, 1967. Holm, R., and Storp, S., Appl.Phys., 1976, 9, 217. Jorgensen, C. K., and Berthou, H., Discuss. Faraday Soc., 1972, 54, 269. Seah, M. P., and Dench, W. A., Surf. Interface Anal., 1979, 1, 2. Briggs, D., in West, A. R., Editor, “Proceedings of the 6th Conference on Molecular Spectroscopy,” Heyden, London, 1977, p. 468. Holm, R., and Storp, S., in West, A. R., Editor, “Proceedings of the 6th Conference on Molecular Spectroscopy,” Heyden, London, 1977, p. 482. Storp, S., and Holm, R., J . Electron Spectrosc., 1979, 16, 183. Storp, S., and Holm, R., Surf. Sci., 1977, 68, 10. Ohnsorge, J., and Holm, R., Med. Prog. Technol., 1978, 5, 171. Storp, S., and Holm, R., in Dobrozemsky, R., Riidenauer, F., Viehbock, F. P., and Breth, A., Editors, “Proceedings of the 7th International Vacuum Congress and 3rd International Conference on Solid Surfaces, Vienna, 1977,” Volume 111, p.2255. Holm, R., and Storp, S., Surf. Interface Anal., 1980, 2, in the press. Analysis of Biological Surfaces P. Echlin Department of Botany, University of Cambridge, Cambridge, CB2 3EA The characterisation of a surface involves more than obtaining high-resolution topographic images along the x andy co-ordinates, and the chemical identity of the surface layer of atoms. It should also include a co-ordinated in-depth analysis along the z-axis at as high a resolution as can be obtained with a particular form of instrumentation. Surface characterisation tech- niques may be divided into those methods covering microtopography and those involved in chemical characterisation.The former category is served by optical microscopy and scanning and transmission electron microscopy, while the latter techniques are based on excitation at the surface by photons, electrons and ions. A surprisingly large number of techniques are avail- able to the surface analyst and a recent paper by Larrabeel reviewed the 20 or so methods that are currently in use. Unfortunately, only about half of these methods are useful for the biologist, owing primarily to the constraints of the specimen. One of the many special features of living material is that it has extensive internal surfaces that are completely different in structure and function from the external surface at the inter- face with the environment. Much effort has been put into discovering ways to preserve these surfaces so that they can be examined and analysed by different forms of instrumentation.This preservation involves stabilisation of the macromolecular architecture, careful reinoval or immobilisation of the water and, under some circumstances, the introduction of elements of high relative atomic mass to (hopefully!) specific sites in the specimen. The perfect preparative technique aims to transform the thermodynamically unstable organic matrix into a heat- and radiation-resistant inorganic replica. These procedures result in the production of exquisitely delicate cell architecture but usually at the expense of 99% of the content of living cells being lost during the process. Following preservation, the internal surfaces of biological material may be exposed by a number of means, but only after the mechanical strength and stability of the sample has been enhanced.This may be achieved either by replacement of the cell water by liquid resins, which are then polymerised to a solid, or conversion of the liquid water into a solid phase by means of quench cooling. The strengthened cells and tissues can then be484 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION Anal. Proc. sectioned, fractured or replicated to reveal the internal surfaces. It is apparent that the validity and usefulness of information obtained from biological material examined and analysed in the high vacuum of microbeam instrumentation is very dependent on the preliminary preparative procedure. Of all the methods that have been devised, low-temperature methods show the greatest promise.2 Cryofixation, if properly and conscientiously applied, results in minimum disruption to the cell contents and, more important, leaves the soluble constituents of the cell more or less in their natural location in the cytosol.For the purposes of this discussion, a biological surface will be considered to be 1-2 pm deep. Emphasis will be placed on considering the chemical analysis, i.e., at the elemental, molecular and macromolecular levels, of the biological surfaces and little consideration will be given to the morphological features. Nevertheless, the specimen preparation and analytical techniques must necessarily preserve and display the principal ultrastructural features, if only to allow the analytical data to be related to a particular location in the cell.The transmission electron microscope (TEM) can be used to give analytical information, by virtue of the increased electron scattering from high atomic number inclusions within a low atomic number matrix. The high atomic number material, usually as heavy metals, may occasionally be present as a natural deposit such as an inhaled particle in pulmonary tissue. Under these circumstances the TEM can only indicate that a high relative atomic mass particle is present ; it cannot give information on the precise nature of the inclusion. If the high atomic number inclusion is in a crystalline form, however, it can be identified by means of electron &fraction using the selected area diffraction device fitted to most modern transmission micro- scopes.It is more usual to introduce heavy metals artificially into a specimen either by manipulating known enzymatic reactions so that the end product is a heavy metal deposit or by taking advantage of the affinity of chemical groups for heavy metals. Thus, alkaline and acid phosphatases may be localised by means of a lead deposit, acid mucopolysaccharides by means of iron and nucleic acids as uranyl groups. An alternative approach is to precipitate a low atomic number element as an insoluble heavy metal salt. Silver salts can be used to precipitate chloride, antimony compounds can be used to localise monovalent and divalent cations such as K+, Na+, Ca2+ and Mg2+, and PO,- can be precipitated as salts of lead. A recent book edited by Hall3 reviews many of these methods.These three approaches, of positive staining, enzyme chemistry and precipitation, can be used only qualitatively because of the difficulty of objectively assessing differences in electron density in a tissue section. The scanning electron microscope can give much more chemical information about a specimen, if only because of the multiplicity of signals that may be obtained from the specimen after its interaction with the primary electron beam. Goldstein and Yakowitz* reviewed the methods that are available. The most familiar specimen - beam interaction is the secondary electrons, which have an energy of between 0 and 50 eV. They arise from within the first 10 nm of the surface and are the principal source of the signal used to provide morphological information about surfaces using the topographic contrast mechanisms.Under special circumstances the secondary electrons may also be used to obtain chemical information about the specimen. On a highly polished flat surface (where there is minimum topographic contrast) there is sufficient difference in atomic number contrast between elements that are widely spaced in the Periodic Table to separate them from one another. I t has been possible, for example, to localise copper inclusions in a highly polished aluminium matrix by virtue of differences in secondary electron emission at 5 and 20 kV. This approach has not been applied to biological specimens as it is difficult to obtain a smooth, highly polished surface. In a rather round-about way the topographic contrast mechanism has been used to obtain chemical information about surfaces.Sites of differing antigenic specificity may be localised on a cell surface using standard immuno- logical techniques. Instead of using a fluorescent probe, a morphologically recognisable marker is attached to the antibody, and the specific antigenic sites may be localised by recognising the structural marker. By using the bacteriophage T,, it has been possible to map out specific antigenic sites on the surface of red blood cells. Silica spheres of a known and consistent diameter have also been used for the same purpose. It is more useful, however, to use the back-scattered primary electrons for simple qualitative analysis. The back-scattered primary electrons suffer only a small energy loss during interaction with the specimen, but the amount of scattering is, to a first approximation, a function of atomic number.Thus, a heavy metal inclusion in a low-density matrix will give an increased signal from its surroundings, andivOVembeY, 1980 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION 485 this method, when combined with the wet-chemical localisation methods discussed earlier, can provide useful analytical information about biological surfaces. Thus, tantalum inclusions have been localised in pulmonary tissue, and the sites of certain pancreatic enzymes have been identified by means of lead deposits. As with other methods that have already been discussed, the back-scattered imaging technique is only qualitative and cannot give information directly on the chemical identity of the inclusion.The scanning electron microscope can also give information about the molecular and macromolecular composition of a biological surface by measuring the cathodolztmznescence, which arises from the interaction of most biological materials with a high-energy electron beam- The wavelength of the emitted photons is characteristic of a particular molecular species, and provided that care is taken in measuring the wavelength and energy of light the method can be used seniiquantitatively. Cathodoluminescence can be used to analyse natural surfaces, and has been used, for example, to map the location of herbicides on leaves, and to follow the distribution of zinc sulphide particles within an organic fossil matrix.Cathodoluminescence has been used to localise artificially introduced fluorescent dyes that have an affinity for particular chemical groups. Quinacrine dihydrochloride has been used as a probe for cells from vaginal smears and acridine orange can be used to localise nucleic acids. At first glance, cathodoluminescence would appear to be an ideal method for examining the surfaces of mem- branes. The difficulties arise in the application of suitable fluorescent probes, and the fact that the cathodoluminescent yield is usually low. The latter problem can be overcome by using larger probe sizes and an increased probe current, but only at the expense of specimen damage and diminished spatial resolution owing to the increased size of the interactive volume. I t is only when we turn to X - r a y microanaZysis that it is possible to realise the analytical potential of electron beam instrument^.^ X-rays are produced when an electron beam of sufficient energy strikes any material.The X-rays that are produced have a characteristic energy and wavelength for each element, and this feature is the basis of the X-ray analytical technique. The X-rays may be collected and measured using a wavelength-diff racting spectrometer and/or an energy-dispersive spectrometer. The former method has a high analytical resolution and can readily separate closely related elements, but only at the expense of analysing each element in sequence. The energy-dispersive spectrometer has a lower analytical resolution, but is able to analyse and display all of the elements simultaneously, which is particularly useful if one wishes to obtain information relating to the total elemental composition of the specimen.X-ray microanalysis gives information about the distribution and concentration of elements, and with a few minor exceptions makes no distinction between elements that are covalently bound within the biological matrix, in an ionised state in the cell fluids or in the form of a crystalline inclusion. It must also be remembered that there is frequently a disparity between the number and type of X-rays generated within the specimen, emitted from the specimen and measured by the detecting systems. This disparity is due to problems of secondary fluorescence, absorption of soft X-rays and the production of spurious signals from the immediate environment surrounding the site of analysis. Much effort is being made to refine the quantitative procedures and we are now at the point where it is possible under some circumstances to detect 0.1 ag (10-19 g) of an element with an analytical spatial resolution of 25 nm.The spatial resolution is greatest in thin sections, and quickly decreases if the analysis is carried out on bulk samples. Within the context of our 1-2-pm thick biological surface, the spatial resolution is probably about 100 nm. Most elements of biological interest can be analysed using X-ray microanalysis. It becomes progressively more difficult to carry out quantitative analysis on light elements, and sodium (2 = 11) is the practical lower limit. X-ray microanalysis may be carried out using a wide range of electron-beam instruments, and it is usual to find one or both types of X-ray detector attached to scanning or transmis- sion electron microscopes, rather than to find the analysis being carried out using a purpose- built and dedicated electron microprobe.X-ray microanalysis can usefully be carried out at different levels of sophistication. In its simplest form it can be used in conjunction with a scanning electron microscope to map the distribution of elements within a section of a sample or on its surface. It can be used to measure relative concentrations of elements in different parts of the specimen and, in conjunc- tion with the appropriate standards, can be used to measure absolute concentrations.486 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION Anal.Proc. The final quality and biological significance of X-ray microanalysis is dependent on two factors. It is entirely dependent on the specimen preparation procedures, the prime aim of which must be to retain the elements in their natural position and natural physiological concentration in the tissues. In this context compromises have to be made, as the preparative procedures lack the sophistication and potential accuracy of the analytical procedures. The quality of the analysis also relies on the way the raw X-ray data are handled and it is here that considerable advances have been made. Thanks to microprocessors and sophisticated com- puter programs, it is now possible to de-convolute the complex spectra that emerge from an X- ray microanalyser and express the data as elemental concentrations, free from the influence of overlapping spectra, background signal and instrumental variations. One of the limitations of X-ray microanalysis is the difficulty associated with the analysis of light elements.These limitations are to a large extent compensated for by using transmission eZectron energy-loss spectroscopy. In this technique, described in a recent paper by Joy and Maher,B one detects and measures the changes in energy or momentum which electrons undergo from exciting X-rays or ionising atoms as they pass through a specimen. From the point of view of microanalysis, the most interesting portions of the energy loss spectra are in the 0-10 eV range, as this region provides the most information about the elemental composition of the specimen.By placing an energy-loss spectrometer below the specimen it is possible to obtain the distribution of energy losses within the specimen. This spectrum is characteristic of the material being irradiated and, provided that the probe diameter of the incident beam is sufficiently small (about 10 nm), high spatial resolution analytical information can be obtained about biological material, particularly for the light elements (2 = 1-20). By using a high- brightness electron source, such as is available from a field emission electron gun, it is possible to extend this method to electron microspectroscopy, by means of which specimen volumes of only a few nanometres diameter may be analysed.' Characteristic energy-loss spectra of thin films of DNA, haemoglobin and lecithin have been obtained using this method, and recent studies have demonstrated the presence of iron in groups of ferritin molecules.The spectra one obtains from transmission electron energy-loss spectroscopy and electron microspectroscopy are similar in nature to the spectra of ejected photoelectrons observed in electron spectroscopy for chemical analysis (ESCA) . Auger spectroscopy has been used for some time by materials scientists8 to analyse the sur- faces of solids. When a beam of electrons of sufficient energy strikes a sample, electrons may be ejected from atoms of the sample, leaving orbital vacancies behind. The atoms are now in an excited state, and the vacancies are quickly filled with electrons from an outer shell of the atom.At the same time an X-ray photon is emitted whose energy corresponds to the difference between the two orbital electrons. This X-ray photon is either emitted from the sample, and is the basis for X-ray microanalysis, or its energy is transferred to another orbital electron which is ejected from the atom. The Auger electrons have energies berween 0 and 1000 V and can be analysed and measured to give elemental information about the micro- volume from which they were emitted. Auger spectroscopy is an extraordinarily sensitive method for analysing the surfaces of material, for although the area covered by the electron beam might be larger than found in X-ray microanalysis, the depth from which the signal comes is limited to a few atomic layers below the surface.The method is very sensitive to contamina- tion, and must be carried out in an ultra-high vacuum (13 nPa), and for this reason alone there have been very few applications to the biological sciences. Some recent studies by Janssen and Venables9 have done little more than show that red blood cells contain carbon. These disappointing results are a consequence of difficulties in specimen preparation and surface charging rather than limitations of instrumentation. Another microscope - analytical system familiar to materials scientists for examining sur- faces is Photoemission microscopy. In this technique, the specimen itself is the source of electrons, and these are generated by either bombarding the surface with UV photons or heating the surface to the point where electrons are emitted.It is possible to examine thin sections of biological material mounted on a metal surface with a spatial resolution of about 20 nm.lo Histochemical analysis may be carried out by specifically staining cell constituents with organic compounds that have a high emission of photoelectrons during exposure to UV radiation. Alternatively, it is possible to localise regions of specific activity by immuno- fluorescent probes, which give a strong and characteristic signal in UV light. Although there are a number of other analytical techniques that use electrons, they have notNovember, 1980 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION 487 yet been applied to biological material and, because of the technical constraint imposed by specimen preparation, are unlikely to be used in the immediate future.There are, however, other analytical systems that make use of high-energy particles, and some of these methods are beginning to have important applications in analysing biological surfaces. High-energy, i.e., 3-MeV, beams of nuclear charged particles such as protons, deuterons and alpha particles can be focused to spot sizes of about 1 pm in diameter. The nuclear microbeam methods induce nuclear reactions in the target material that can be identified by the gamma emission. Elastic scattering can be used to identify elemental distributions across the surface to a depth of 10 nm. Nuclear reactions induced by He3 ions are suited to light elemental analysis, and it has been possible, for example, to identify the location of a protein in a sample on the basis of the nitrogen distribution.11 Because nuclear reactions give a measure of the interaction of the incident ion beam with a specific isotope, the method can also be used as a means of isotope analysis.A unique advantage of the nuclear microprobe method is that the high beam energy allows biological material to be examined in the air and not within the high vacuum of the instrument column. A related technique is secondary i o n mass spectrometry, in which a low- energy (30 kV) ion beam is used to form an image of the surface either by means of a scanning probe or by a direct focusing system. The technique is especially useful for light elements, the secondary ions liberated from the surface being analysed by a mass spectrometer.Quantita- tive analysis is difficult because the spectra from biological samples are notoriously difficult to analyse, but some success has been obtained in measuring isotope ratios. Secondary ion mass spectrometry has been used extensively to investigate the distribution of toxic metals in biopsy tissue, and the information is usually displayed as a series of elemental maps that can conveniently be superimposed one upon another. It is a very sensitive technique and has been used to show the distribution of sodium in nucleated red blood cells, fluorine in calcified tissue and beryllium in pulmonary tissue.12 Many surface studies require an elemental analysis with sub-parts per million sensitivity and a spatial resolution of less than 1 pm.Although electron beam and ion microprobes are useful in this respect, the former is insensitive to light elements and the latter has a poor spatial resolution. The laser microprobe mass apzaZyser goes some way in bridging this gap. Lasers can be used to evaporate and ionise materials in spots as small as 0.5 pm and with a detection limit of 1 part in 107. The sample, usually in the form of a thin film, is bombarded by a finely focused laser beam and the ions are extracted from the underside for analysis using a time-of-flight mass spectrometer. Although still in its infancy, the laser microprobe has been used to study the concentration ratios of Na+, K+ and Ca2f in small bundles of 5-10 muscle fibres maintained in a physiological active state before being quench frozen.More recent work13 has investigated the distribution of lithium in brain tissue, and measured trace amounts of calcium and barium in bovine and feline retinal tissue. As already discussed, the success of the analytical techniques that have been described are very dependent on the preparative methods. There are, however, still further hazards, and these centre around the specimen damage brought about by the interaction of the high-energy beam with the specimen. This damage may range from volatilisation of thermolabile sub- stances, radiation damage, mass loss from the specimens and even selective loss of elements from the sample. The problem is particularly serious for biological material, although many of the losses can be diminished by holding the specimen at low temperatures (123 K) during examination and analysis. It will also be realised that the different analytical techniques cause varying degrees of specimen damage.Thus laser microprobe analysis totally destroys that part of the specimen being analysed. Secondary ion mass spectrometry and photoemission microscopy are progressively erosive through the specimen surface. The deleterious effects of X-ray microanalysis are more insidious and care must be taken to monitor mass losses and elemental losses during the analytical procedures. Transmission and scanning electron microscopy are usually less damaging, although the effects are more marked with the increase in amount of energy put into the sample. It will be noted that only a few references have been given in this brief review, an omission which has been deliberately contrived. Many of the methods described are in common use by biologists, and are being applied to a wide range of cell and tissue surfaces.Under the circum- stances, the reference list below consists mainly of broad reviews that contain further informa- tion about the techniques and the preparative methods. Biologists are offered many highly sensitive analytical tools, but are usually unable to take full advantage of the instrumentation because they are unable to prepare the specimens adequately. They need help, and look to488 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION ‘4nal. Proc. ligand chemists, polymers scientists and analysts to provide the methods to convert their thermolabile, wet, three-dimensional thermodynamically unstable specimens, into dry, stable, radiation-resistant sections that can withstand high vacuum and high temperatures. 1 .2. 3. 4. 5 . 6. 8. n 9. 10. 11. 12. 13. References Larrabee, G. B., Scanning Electron Microsc., 1977, 1, 639. Echlin, P., Ralph, B., and Weiber, E. R., Editors, “Low-temperature Biological Microscopy and Microanalysis,” Royal Microscopical Society, Oxford, 1978. Hall, J . H., Editor, “Electron Microscopy and Cytochemistry of Plant Cells,” Elsevier - North Holland, Amsterdam, 197 8. Goldstein, J . I., and Yakowitz, H., Editors, “Practical Scanning Electron Microscopy,” Plenum, New York, 1975. Hren, J . J., Goldstein, J. I., and Joy, D. C., Editors, “Introduction to Analytical Electron Microscopy,” Plenum, New York, 1979.Joy, D. C., and Maher, D. M., Science, 1979, 206, 162. Isaacson, M. S., and Crewe, A. V., A n n u . Rev. Biophys. Bioeng., 1975, 4, 165. Davis, L. E . , McDonald, N. C., Palmberg, P. W., Riach, G. E., and Weber, R. E. “Handbook of Auger Electron Spectroscopy,” Second Edition, Physical Electronics Inc., Eden Prairie, Minn., 1976. Janssen, A. P., and Venables, J . A., in “Scanning Electron Microscopy,” SEM Inc., A. M. F. O’Hare, Pfefferlrorn, L., Weber, L., Schur, K., and Oswald, H. R., in “Scanning Electron Microscopy,” 1IT Pierce, T. B., in Echlin, P., and Kaufmann, R., Editors, “Microprobe Analysis in Biology and Medi- Galle, P., and Lefevre, R., in Echlin, P., and Kaufmann, R., Editors, “Microprobe Analysis in Biology Kaufmann, R., Hillenkamp, F., Wechsung, R., Heiner, H.J., and Schurmann, M., in “Scanning Ill., 1979, Vol. 11, pp. 259-278. Research Institute, Chicago, Ill., 1976, Vol. 1, p. 129. cine,” Microsc. Acta, 1978, Suppl. 11, pp. 318-330. and Medicine,” Microsc. Acta, 1978, Suppl. 11, pp. 341-354. Electron Microscopy,” SEM Inc., A. M. F. O’Hare, Ill., 1979, Vol. 11, pp. 279-290. Surface Analysis by Glow Discharge R. Berneron and J. C. Charbonnier I R S I D , 185 Rue d u President Roosevelt, 78105 S t . Germain-en-Laye Cedex, Frame Introduction The physical and chemical properties of the surface layers of metals condition their behaviour with respect to corrosion, oxidation, friction and abrasion, as well as to the adherence of protective coatings. It is thus essential for the metallurgist to determine the chemical composition of the metal surface at the various stages of the production (particularly the heat or thermochemical treatment) of the metal through the use of a fast and accurate analytical method.The glow discharge source, in addition to having the advantages of conventional sources (arc and spark), makes the instantaneous analysis of extremely fine metal layers possible and represents, in fact, a surface analysis method. After reviewing the principle characteristics of glow discharge spectroscopy (GDOS) for elemental analysis as well as surface analysis, examples of results obtained in industrial and laboratory studies are given. Glow Discharge Source Operating Principle Emission is obtained by means of a Grimm 1amp.l This lamp consists of a diode-type discharge tube, the anode and cathode of which have a very particular geometry.The sample to be analysed serves as the cathode and seals the lamp. When the argon pressure maintained in the lamp enclosure is in the neighbourhood of a few Torr, the application of a d.c. voltage between the anode and the cathode (1OOOV) makes it possible to establish a glow discharge. The analysed area (about 50 mm2) then undergoes ion bombardment, which leads to regular erosion. The dislodged atoms end up in the plasma, which then emits radiation consisting of the characteristic lines of the elements contained in the sample and the lines of argon.November, 1980 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION 489 The light emitted by the plasma is dispersed by a grating and the monochromatic rays of the elements to be analysed are detected by electron photomultipliers; the signals coming from the latter are amplified and passed through a multiplexer to a processing computer.In our analytical program, 45 elements can be analysed simultaneously and instantaneously. Application to Surface Analysis In order to determine the distribution of an element as a function of the distance to the surface, one need on137 record as a function of time the intensity of a suitably chosen charac- teristic line. However, in order for the method to be quantitative concentration must be related to light intensity, and eroded depth to duration, using commercial or prepared com- pounds as standards. For layers of complex structure it is difficult to determine a concentration and an erosion rate, so that care must be exercised before a value is accepted.For this reason, in many instances, only the intensity of the light emitted as a function of erosion time is indicated. Sputtering Rate intensity and a given argon flow-rate, the sputtering rate is constant. nevertheless not the same for all materials. For surface analysis, the current intensity must be set at a given level. For this current This last rate is Depth Resolving Power Considering the relatively large size of the area under bombardment, one may wonder what the depth resolving power is during the scanning of a concentration profile. As the sputtering rate is fairly high, the depth resolving power is limited by the rate at which the intensity emitted by the plasma is recorded and processed. With the equipment that we use, the theoretical limit of the resolving power is about 0.5 nm.In fact, other factors are involved in practice.2 Scanning Time In fact, the dislodged atoms go through the plasma and are entrained in the working gas of the lamp. They are deposited at various different points, in particular on the anode and on the peri- phery of the sample facing it. After a certain time this results in a short circuit and hence in an interruption of the analysis. In reality, several seconds of sputtering are often sufficient for the scanning of a surface concentration gradient. Erosion time is not, in principle, limited. In practice, a limitation does exist. Examples of Results Obtained Heat Treatment at High Temperature The compositions of scales formed on many grades of steel have been determined.3 Decarburisation profiles following heat treatment have also been obtained. For deep decarburisation the procedure involves the abrasion of layers of 0.05 mm and for shallow decarburisation carbon analysis is carried out contin~ously.~ Thermochemical Treatment GDOS has been used for analysis of case hardening, nitriding and carbonitriding layers. Concentration profiles of nitrogen, oxygen and carbon for different nitriding processes have been pre~ented.~ Study of Surface Segregation on Thin Sheets After Annealing5 During annealing, certain elements are oxidised after they have diffused to the surface. Fig. 1 shows this phenomenon clearly for manganese, chromium, silicon and aluminium. These results are in good agreement with those obtained by Leroy using Auger spectroscopy and secondary ion mass spectroscopy.6490 MODERN TECHNIQUES FOR SURFACE CHARACTERISATION Anal. Proc. v) C 3 +4 .- 2 2 f s * .- v) 01 C c. .- w - 0 0.2 0.4 0.6 Thicknesdpm Composition profiles in oxide layers formed on a sheet steel during annealing. Variation of light intensity of the elements as a function of sputtering time. Fig. 1. Study of the Properties of Phosphate Coatings these conversion coatings. semi-quan ti tative results. Surface Conditioning Inspection Glow discharge spectroscopy is an extremely powerful method for revealing modifications in composition following various surface treatrnent~,~,' viz., machining, grinding and chemical or electrochemical polishing. Study of Passivation Processes only a few nanometres thick.8-10 Few surface analysis methods give reliable results because of the particular structure of Owing to the large area analysed (about 50 mm2) GDOS gives GDOS also makes it possible to determine the distribution of elements in passive layers It has been shown that the results obtained by this 0 I I I I I I I I I t 0 0.2 0.4 0.6 0.8 1 1.2 Erosion t imeis I I , I I I I 1 I I I 0 1.5 3 4.5 6 7.5 9 Wavelengthinm Fig. 2 . solution. time. Composition profiles in a film formed on iron in boric acid buffered Variation of light intensity of the elements as a function of sputteringNovembeY, 1980 EDUCATING FOR PROFESSIONAL RESPONSIBILITIES 491 technique are in good qualitative agreement with, and also complement those obtained by, more conventional surface analysis methods (e.g., AES, SIMS). As an example, Fig. 2 gives the distribution profiles in a film formed anodically on pure iron in boric acid buffered solution (pH 8.4). Conclusion The simplicity and speed of GDOS make it a very attractive analytical method, in particular for inspections of the state of the steel surface at various manufacturing stages, developing thermochemical surface treatments and corrosion protection processes, and laboratory studies dealing with passivation processes. 1. 2. 3. 4. 5 . 6. 7. 8. 9. 10. References Grimm, W., Sfiectrochim. Acta, 1968, 23B, 443 Berneron, R., Spectrochim. A d a , 1978, 33B, 665. Berneron, R., and Moreau, J . P., Contrat CECA 6210/GA/308, Rapport RE 528, 1978; Circ. Inf. Berneron, R., Manenc, J., Michel, H., and Gantois, M., Me‘m. Sci. Rev. Meltall., 1979, 109. Mathieu, S., and Berneron, R., “Proceedings of Survimet, Strasbourg, 1978,” RE 529, IRSID, Servais, J. P., Graas, H., and Leroy, V., Circ. Inf. Tech., Cent. Doc. Szder., 1976, 33, 1069. Berneron, K . , Caplet, J . I.., Charbonnier, J. C., and Cretin, J., Me‘m. Sci. Rev. Me‘tall., 1978, 503. Berneron, R., Charbonnier, J. C.. Namdar-Irani, R., and Manenc, J., Rapport RE 538, 1978; Alexandre, B., Berneron, R., Charbonnier, J . C., and Manenc, J., Surf. Technol., 1979, 9, 317. Alexandre, B., Berneron, R., Charbonnier, J . C., Namdar-Irani, K., and Nevot, L., Paper presented Tech., Cent. Doc. Sider., 1978, 35, 2249. Saint Germain en Laye, France, 1978. Corros. Sci., to be published. a t “ JournCes d’Automne 1979”; Rev. Meltall., to be published.

ISSN:0144-557X    

DOI:10.1039/AP9801700467

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

November, 1980 EDUCATING FOR PROFESSIONAL RESPONSIBILITIES 491 Educating for Professional Responsibilities The following is a summary of one of the papers presented at the RIC Symposium at the Congress. The Training of Analytical Chemists W. I. Stephen Department of Chemistry, Univevszty of Birmingham, P.O. Box 363, Birmingham, B15 2TT No-one at all conversant with the international literature of analytical chemistry need have any doubts about the value of analytical chemistry to most spheres of chemical endeavour. Analytical Abstracts, the monthly journal published by the Royal Society of Chemistry, publishes around 10000 abstracts each year of papers on all aspects of analytical chemistry, so the size and functionality of analytical chemistry on a world-wide basis is not a matter for dispute.Far less obvious and less well defined is the educational process, particularly in the UK, which results in the production by our educational establishments of trained analytical chemists, and it is this matter which I have been asked to comment upon. What I have to say is largely personal opinion for which I make no apology, but it is conditioned by more than 30 years’ experience as a professional analytical chemist. He really is no different from any other chemist, except that he has an especial interest in the applications of chemistry to solve particular problems concerning the composition of matter. Like any other chemist, he has elected to follow some degree of specialisation, which really is the culmination of his basic education in chemistry. That analytical chemistry is relevant to many of the social and economic situations that confront mankind today, one would think hardly needs emphasising. Never- theless, there appears to be more than the usual difficulty in recognising the status of analytical chemistry in many educational establishments that profess chemistry departments, particularly in the UK.There is a distinct reticence on the part of these chemistry depart- ments to recognise the disciplines necessary in the teaching of analytical chemistry whilst What, then, is an analytical chemist?492 EDUCATING FOR PROFESSIONAL RESPONSIBILITIES Anal. Proc. happily segmenting other aspects of chemistry into well defined categories on the grounds that these are more fundamental to the science.This has resulted in situations where analytical chemistry finds itself absorbed by and subservient to the other main branches of chemistry, to its detriment and to the detriment of the number of new graduates in chemistry who find little to attract them to a career in analytical chemistry. Happily, this is not a universal attitude and some universities now recognise the importance of the sound philo- sophical approach to the teaching of analytical chemistry that can be achieved by enthusiastic specialist teachers. The need to consider analytical chemistry as an essential part of the total education of chemists equally with other branches of chemistry is again self-evident, certainly on the basis of relevance. Analytical chemistry has had relevance for more than 200 years (and much longer in a purely historical context), before many of the now well established divisions of chemistry were created.Therefore, in no way need analytical chemists bow before their supposedly more august brethren in other branches of chemistry. I have, during my career as a professional chemist, recognised the need to integrate the teaching of analytical chemistry with the other branches of chemistry at undergraduate level, and I have been fortunate enough to have had a fairly free opportunity to practise this in the University of Birmingham where special factors allowed the growth of an active division of analytical chemistry to occur. This situation has enabled my three colleagues and myself to teach the principles and practice of analytical chemistry at each level of the honours chemistry course, and to other courses such as metallurgy and biochemistry.Whilst the disciplines of quantitative chemistry may not always appeal to individual students, nevertheless it instils in them a respect for accuracy and precision, the watchwords, inci- dentally, of the Analytical Division of the Royal Society of Chemistry. With opportunities for establishing greater relevance through, for example, optional final year courses in environ- mental chemistry, instrumental methods and trace metal analysis, the teacher can readily show the need for a wide range of analytical methodology. Moreover, the way in which the analytical chemist develops and applies his methods becomes apparent to the interested student.The importance of the sample and the procedures for ensuring the representative nature of the sample are brought home to him long before he finds himself confronted by some awkward analytical problem during his early days in industry. But I am talking, at least from a university standpoint, about the exception rather than the rule, and if British industry were to be dependent on British university chemistry graduates, in general, to undertake the control and mmagement of specialised analytical chemistry laboratories, then it would also need to consider further training to eliminate many of the deficiencies that these graduates possess. In this respect, the polytechnics are better placed in that their curricula for an Honours degree are far less conventional and tradition bound than in universities.Opportunities exist for degree courses in chemistry in which analytical chemistry plays a very significant role. As an external examiner for some years to such CNAA courses, I can appreciate the excellent work done in these poly- technics and the high standards of chemical education that are involved. Of course, one might (and many will) argue that such training is applied chemistry and not entirely suited to the more erudite pursuit of pure science. But this is a fallacy, for chemistry is very much an applied science except for the work of the very few real innovators of genius who do their own things regardless of their particular environments. So even in universities the application of chemistry to the solution of analytical problems should be part of the over-all educational pattern, recognised as such, and not left to the more aware student to sift from the mass of often unconnected chemical knowledge that he acquires during his studies.There are some who believe that the training of analytical chemists is best left to specialist graduate courses, particularly the one-year MSc courses. Whilst these have an important role in the general chemical educational system, only six such courses in analytical chemistry in the UK are recognised by the Science Research Council for the award of its Advanced Course Studentship. Twenty-three quota awards were made in 1979, of which sixteen were allocated to two of the courses, and the remaining seven to the four other courses. It is to be hoped that cuts in public spending will not seriously exacerbate the somewhat precarious position of some of these courses.Without SRC support, their viability is in doubt and their cost-effectiveness is related not only to this, but to the over-all student numbers, madeNovember, 1980 EDUCATING FOR PROFESSIONAL RESPONSIBILITIES 493 up largely by graduates from overseas and often from Third World countries with no petro- leum revenues to subsidise the realistic academic fees that these students will be obliged to pay next session. Courses will disappear to the detriment of the home students and the teachers who have devoted much time and energy to maintaining the high quality of these courses. Perhaps, I am being overly pessimistic, but already there is sufficient evidence from our own course at Birmingham that applications for admission next October are well down on previous years.That SRC is aware of some of the problems associated with its support (or lack of it) for analytical chemistry is made clear in its recent (December 1979) Chemistry Committee Newsletter. This contains the report of the Analytical Science Panel set up to advise the Chairman of SRC and the Chief Scientist and Engineer of the Department of Industry whether there is a need for any initiative in the field of postgraduate education in analytical science. The report makes interesting and encouraging reading for teachers of analytical chemistry, with such requirements as the adoption of a more positive approach to the teaching of the subject, for example, possibly by the establishment of new chairs in Analytical Science, and the recognition of the need for staff having a genuine commitment in the area to describe themselves as analytical chemists.Deeds not words are now expected( !) and is “analytical science” that much more euphemistic a term than the time-honoured “analytical chemistry,’’ which seems so out of favour with many university professors of chemistry? Or are we now set to produce a race of machinists to whom the very nature of chemistry and chemical reactions is something akin to anathema? Better men than I have over the years tried to pin down the reasons for the reticence of our universities to recognise the individuality of analytical chemistry. Some few weeks ago, I attended a mock trial at which universities were charged with deni- grating the profession of analytical chemistry.The charge was sustained, although my own feeling was for the Scottish verdict of “not proven.” I did think, however, that a more appropriate, more insidious and hardly lesser charge would be that universities have in the past neglected and in recent times discriminated against the profession of analytical chemistry. Anyone who disbelieves me, let him look at the facts. The first and only established chair of analytical chemistry in the UK was created in 1958. At the present time there are only four incumbents in chairs in the 58 universities in the UK, with one professor-elect, and only two of these are established chairs. The demise of the once flourishing and internationally recognised Imperial College School is now imminent.The rise and fall of this important source of well trained analytical chemists has occurred within a time-scale covered by the relatively short tenure of its only professor, T. S. West, whose School has been fighting, unsuccessfully, to retain its identity since West resigned from the chair; and, one might ask, is a similar fate to befall Birmingham in the post-Belcher period? This I can only hope, is less likely, but the portents are not by any means good. You might ask, and rightly so, what all this has to do with the training of analytical chemists. I believe, and my colleagues support this contention, that without dedicated and enthusiastic teachers whose interests are maintained by personal research and a full involvement in professional affairs, what effective teaching of analytical chemistry that does occur in our universities will decline and an important source of trained analytical chemists will rapidly dry up.Of course, the Universities have no monopoly on this aspect of chemical education, but they do have a responsibility to set the pace which others follow. The lack of chairs undoubtedly influences career prospects, and is, in my opinion, a prime reason for the reticence of all but the brave or foolhardy to follow academic careers in analytical chemistry. R. Belcher has recently talked about the resurgence of analytical chemistry in this country during the past 25-30 years, except perhaps in its teaching, compared with the situation abroad. This really is a foolish situation for a country with an industrially based economy such as ours to allow to exist.As our technologies develop, the need for analyses of materials and products becomes ever more important. Often those requiring the analyses are those knowing less and less chemistry, mainly because of the difficulties in maintaining adequate amounts of chemistry in many academic courses, say, in engineering, and other applied sciences. This means that in many industria1 situations, the chemists in what may essentially be the analytical laboratory are rapidly becoming the sole repositories of chemical knowledge within the company. This again emphasises the role of the analytical chemist as primarily a professional chemist and not a The pressures on curricula are just too great.494 EQUIPMENT NEWS Anal.Proc. trained chemical analyst or machine manipulator. The chemical knowledge that he possesses goes far beyond the straightforward requirements for routine analyses and allows him to make an increasingly important contribution to the successful pursuit of his company’s business. I believe it is true to say that the general quality of such publications arising from UK sources is much lower than those arising from countries where there is a long tradition of university chairs in analytical chemistry as in the USA and most of our European neighbours. Academic status is important and highly relevant to those concerned with the teaching of the subject. No status-no resources, and consequently little or no research.With little or no encourage- ment within academic institutions, what chance has the interested young scientist to acquire a sound training in analytical chemistry? Let me quote a short passage from an interesting lecture that deals most admirably with the problem. “Having very briefly touched on the nature and extent of the scientific equipment needed for the successful practice of analytical chemistry, we may reasonably inquire whether the training which our young professional chemists obtain is such as is calculated to insure the best results. . . . analytical chemistry ought clearly to take an outstanding position in our universities and university colleges, as it is from them that, more often than not, the young chemist proceeds directly to the practice of his profession.Unfortunately, the position which it takes in those institutions is not, as a rule, a high one, nor one at all commensurate with its importance. I believe I am correct in saying that in no university in this country does a chair of analytical chemistry exist, and that a subject which is admittedly of such great importance is entrusted to teachers who, however well qualified and capable they may be, have as a rule to teach it, if I may use the expression, incidentally. . . . So large a subject, and one which is in constant process of development, might well, it seems to me, be entrusted to a specially appointed professor, who would have the opportunity of keeping himself fully abreast of the developments of his subject, and who would have the time to deal with it in a manner practically impossible under the existing conditions. ’ ’ Although these words were spoken 65 years ago by Alfred Chaston Chapman, an illustrious President of the Institute, they might equally well be said today. Such then is progress! The problems have been recognised and various answers given. Can we now look for some action in the improved climate created by the Royal Society initiative and the SRC report. Whilst fervently hoping for this action, like Chaston Chapman, I am not so foolish as to imagine that the creation of chairs of analytical chemistry in our universities would bring forth a new heaven or a new earth, but at least we can be certain that this universally important branch of chemistry would be taught under significantly better conditions than those which largely exist at present. I began this paper with a mention of published work in analytical chemistry.

ISSN:0144-557X    

DOI:10.1039/AP9801700491

出版商:RSC    

年代:1980

数据来源: RSC

摘要:

494 EQUIPMENT NEWS Anal. Proc. Equipment News Atomic-absorption Spectrophotometers Models 2380, which replaces Models 380 and 560, and 2280, replacing Model 280, both include microprocessor facilities. Model 2280 has the single-beam optical system of Model 280, and Model 2380 the optical configuration of Models 380 and 560 together with auto-gain control and, using a D, arc background correc- tor, automatic intensity control. Insert 501 on the Reader Enquiry Service form for further information. Perkin-Elmer Ltd. Conductivity Monitors A range of conductivity monitors, designated Style B, 910-915 Series, features 23 models, with spans ranging from 0.2 to 20000 pS cm-l in linear single- and multi-span and non-linear single-span models. Foxboro Analytical. Insert 502 on the Reader Enquiry Service form for further information.Oscilloscope The 0s 1100A, a 30-MHz dual-trace oscillo- scope, incorporates an 800 x 100 mm cathode- ray tube with a 10-kV accelerating potential; it also has a trigger-delay facility. The dual- channel has sensitivities switchable from 2 mV to lOVcm-l, time-base speeds of 200ns to 2 s cm-l and a x 10 magnification t o give aNovember, I980 EQUIPMENT NEWS 495 fastest sweep of 20 ns cm-l. Four ranges give delays of 10 ps to 100 ms. Insert 503 on the Reader Enquiry Service form for further information. Gould Instruments Division. Constant Temperature Bath The Guideline Model 9734, a microprocessor- controlled constant temperature bath has a range of - 10 to 110 "C with a stability of 5 2 mK (f0.002 "C). The working volume is 50 1, with dimensions of 550 x 300 x 250 mm, and it is suitable for use with water, oil, fluoro- carbons, alcohols or ethylene glycol.Lyons Instruments. Insert 504 on the Reader Enquiry Service form for further information. Scanner A radio-thin-layer chromatography scanner from Berthold has a 100-fold increase in measuring speed. The LB 282 evaluates radio- TLC plates and electropherograms, being particularly sensitive to tritium and 14C with resolutions of 0.3 and 1 mm, respectively. Measurements are made using a gas flow proportional counter with a 250 x 150 mm aperture, the full length of 20cm TLC or electropherogram plate being examined at one time. A multi-channel analyser allows instan- taneous integration of areas under peaks, back- ground subtraction, etc.Laboratory Impex. Insert 505 on the Reader Enquiry Service form for further information. Chart Drives A range of five hand-wound portable clockwork chart drives offer one revolution in 6 or 24 h, 7 or 31 d and a dual-speed movement of 24 h or 7 d. Horstmann Engineering Products. Insert The escapement comprises 13 jewels. 506 on the Reader Enquiry Service form for further information. Fraction Collector The FRAC 300 can be programmed in the time or volume mode to collect up to 300 fractions. Columns and ultraviolet monitors can be mounted on the unit, which can operate with the P-3 peristaltic pump, UV-1/214, UV-1 and UV-2 ultraviolet monitors, and a chart recorder. Insert 507 on the Reader Enquiry Service form for further information. Pharmacia (Great Britain) Ltd.Chemiluminescence Detector The Biolumat LB 9500, made by Berthold, a high-sensitivity photomultiplier detector, can measure ATP concentrations down to 1 pg in a sample of up to 500 pl. Photon counts are provided by the reaction of ATP with luci- ferase enzyme and substrate. The instrument can operate by manual initiation or by auto- matically adding 100 pl of reagent to the sample and immediately starting the measure- ment. Laboratory Impex. Insert 508 on the Reader Enquiry Service form for further information. Centrifuges Two high-speed micro-centrifuges, the Eppen- dorf 5412 and 5413, have respectively a 12- position rotor accepting 1.5-ml micro-test-tubes or 0.4-ml tubes with an adaptor, and a rotor barrel plus plastic insert divided into four compartments each holding one chain (8 link) section or a test-tube carrier for 10 tubes.Anderman & Co. Ltd. Insert 509 on the Reader Enquiry Service form for further information. Ovens The Series U Memmert ovens are available in eleven sizes with capacities of 14-720 1 using natural convection and the series UL in five496 EQUIPMENT NEWS Anal. Proc. sizes with capacities of 53-7201 using fan- assisted convection. Anderman & Co. Ltd. Insert 510 on the Reader Enquiry Service form for further information. Stirrers The Mk V laboratory stirrers are available with interchangeable motors of 1/15th, 1/20th or 1/30th horsepower outputs; speeds of 0-600 or 0-6 000 rev min-1 are available either via the gearbox or direct from the motor shaft. A heavy-duty model can give single or alternating stirring action with an infinitely variable speed control up to 400 rev min-l.Anderman & Co. Ltd. Insert 511 on the Reader Enquiry Service form for further information. Pressure Regulator The Tescom 44-2400 series of pressure regula- tors are designed for precision metering of high-purity hazardous or corrosive gases. All parts in contact with the material are in 316 stainless steel or Teflon. They can also be Teflon-coated inside and outside, and with a Hasteloy main valve for use with anhydrous hydrogen chloride. Insert 512 on the Reader Enquiry Service form for further information. Techmation Ltd. Portable pH Meter The Model PH-2001 Manning portable pH meter provides a continuous record of pH. Designed robustly to stand up to on-site conditions, it includes a large liquid junction area in contact with the fluid being measured.Three selectable ranges of 0-14, 2-12 or 5-9 pH each have an accuracy of &l% of the range and the unit sensitivity is 0.05 pH. The circular chart is clockwork-driven optionally for 24-h or 7-d operation. The battery is rechargeable in situ. Techmation Ltd. Insert 513 on the Reader Enquiry Service form for further information. Digital Thermometer The Jenway Model 7500 panel-mounted digital thermometer has an operational range of - 220 to + 1 750 "C with a resolution of either 0.1 or 1.0 "C. Four seven-segment Beckman gas discharge displays are used for clarity. An integral alarm facility provides high/low, high/high or low/low alarm indication as required, selectable by a push-button on a pcb-mounted potentiometer.Jenway Ltd. Insert 514 on the Reader Enquiry Service form for further information. Digital Thermometer The D150 series of hand-held digital thermo- meters provide direct or differential tempera- ture readings. The Model D150 has direct temperature range of -50 to +l50 "C, with a single sensor mounted via a jack socket. The Model 1500 has two jack sockets to give direct temperature readings in the range -50 to + 150 "C or using a second sensor, differential reading in the range -100 to +lo0 "C. Resolution in both, which are powered by four miniature silver oxide cells, is 0.1 "C. Channel Electronics (Sussex) Ltd. Insert 515 on the Reader Enquiry Service form for further inform ation. Ultraviolet Lamp An ultraviolet lamp switchable for either 366 or 254 pm singly or jointly or usable with day- light tubes is mobile, readily adjustable and requires no warm-up for the tubes.Whilst designed primarily for use with pre-coated TLC plates, it has many other diagnostic uses. Anderman & Co. Ltd. Insert 517 on the Reader Enquiry Service form for further information. Plug Valves The Nupro P4T series of high flow capacity plug valves have a variety of end connections, e . g . , 1/8-, 1/4- and 3/8-in and 6-mm Swagelok tube fitting, 1/8- and 1/4-in male and female NPT, 1/4-in male NPT inlet to 1/4-in Swagelok tube fitting outlet and 1/4-in male NPT inlet to 1/4-in female NPT outlet. All have a 4.4-mm (0.172-in) orifice in the plug. Standard materials are brass and 316 stainless steel, with ratings to 3 000 lb in-2 and 204 "C.The straight plug is PTFE coated. Insert Manchester Valve & Fitting Co. Ltd.November, 1980 EQUIPMENT NEWS 497 518 on the Reader Enquiry Service form for further information. Temperature Recorders The Series BS250, made in three versions, provides one, two or three channels for hard- copy temperature recording. One channel can be switched either to a thermocouple/thermo- meter signal or to a standard linear system for recording, whilst the other two channels are for standard linear signals only. The series has cold junction compensation and accepts a wide range of plug-in software modules for the standard range of thermocouples. The series BS300 provides two-, four- or six-channel temperature recording.Each version accepts the Pt- 100 thermometer, uni- versal unlinearised thermocouple, NTC thermo- couple and J/K/S/T thermocouple modules. Some units incorporate ice-point compensation. A multi-point version of the BS300 is available for 6-12 channels. Bryans Southern Instruments Ltd. Insert 516 on the Reader Enquiry Service form for further information. Ferrules Graphite ferrules, used to connect glass columns in gas chromatography, can be used to link tubing in diameter from 3/4in to 0.4mm. The smallest size has been developed for the new quartz fused silica columns. Being of combined front and back construction, they obviated the need for conventional back ferrules. Reducing ferrules, e.g., 1/4 to l/lSin, are also available. Chromacol Ltd. Insert 519 on the Reader Enquiry Service form for further information.Isothermal Pack A portable isothermal pack (PIP) attached to the Century System’s Vapour Analysers gives stable temperature control of gas chromato- graphy columns. D. A. Pitman Ltd. Insert 520 on the Reader Enquiry Service form for further information. Fraction Collector The LKB 21 1 Multiracfraction collector is micro- processor controlled to collect by time, drop or volume in millilitres to litres. It is fully com- patible with LC or HPLC systems. LKB Instruments Ltd. Insert 521 on the Reader Enquiry Service form for further information. Porosimeter The Mercury Pressure Macropore Unit 120 SeriFs is used for the analysis of macropores in solid samples, and together with the Mercury Pressure Porosimeter 200 Series, for complete analysis including smaller pores.The Macro- pore unit works from 0 to 3 000 Torr, measuring pores from 1.875 to 600 pm radius. The 200 Series Porosimeter extends the range to 0.00375 pm. Insert 522 on the Reader Enquiry Service form for further information. Erba Science (UK) Ltd. Literature Descriptive literature is available concerning the range of equipment for the analysis and control of oil and petroleum products. EDT Research. Insert 523 on the Reader Enquiry Service form for further information. An application report on the use of an electro- chemical sensing system to control accurately the dilution of bulk caustic soda and a flow chart illustrating the electrodeless ,system is entitled “No. 2 : Chemical Concentration Con- trol.,’ Foxboro‘ Analytical. Insert 524 on the Reader Enquiry Service form for further information. An applications paper describes the “Analysis of Trace and Major Components in Vitamin and Mineral tablets by DC Plasma Emission Spectroscopy,” using the Spectraspan 111. Techmation Ltd. Insert 525 on the Reader Enquiry Service form for further information. A booklet by A. T. Rhys-Williams entitled “Fluorimmunoassay’ ’ reviews various pro- cedures that have been developed. Perkin-Elmer Ltd. Insert 526 on the Reader Enquiry Service form for further information.November, 1980 EQUIPMENT NEWS 497 518 on the Reader Enquiry Service form for further information. Temperature Recorders The Series BS250, made in three versions, provides one, two or three channels for hard- copy temperature recording.One channel can be switched either to a thermocouple/thermo- meter signal or to a standard linear system for recording, whilst the other two channels are for standard linear signals only. The series has cold junction compensation and accepts a wide range of plug-in software modules for the standard range of thermocouples. The series BS300 provides two-, four- or six-channel temperature recording. Each version accepts the Pt- 100 thermometer, uni- versal unlinearised thermocouple, NTC thermo- couple and J/K/S/T thermocouple modules. Some units incorporate ice-point compensation. A multi-point version of the BS300 is available for 6-12 channels. Bryans Southern Instruments Ltd. Insert 516 on the Reader Enquiry Service form for further information.Ferrules Graphite ferrules, used to connect glass columns in gas chromatography, can be used to link tubing in diameter from 3/4in to 0.4mm. The smallest size has been developed for the new quartz fused silica columns. Being of combined front and back construction, they obviated the need for conventional back ferrules. Reducing ferrules, e.g., 1/4 to l/lSin, are also available. Chromacol Ltd. Insert 519 on the Reader Enquiry Service form for further information. Isothermal Pack A portable isothermal pack (PIP) attached to the Century System’s Vapour Analysers gives stable temperature control of gas chromato- graphy columns. D. A. Pitman Ltd. Insert 520 on the Reader Enquiry Service form for further information. Fraction Collector The LKB 21 1 Multiracfraction collector is micro- processor controlled to collect by time, drop or volume in millilitres to litres. It is fully com- patible with LC or HPLC systems.LKB Instruments Ltd. Insert 521 on the Reader Enquiry Service form for further information. Porosimeter The Mercury Pressure Macropore Unit 120 SeriFs is used for the analysis of macropores in solid samples, and together with the Mercury Pressure Porosimeter 200 Series, for complete analysis including smaller pores. The Macro- pore unit works from 0 to 3 000 Torr, measuring pores from 1.875 to 600 pm radius. The 200 Series Porosimeter extends the range to 0.00375 pm. Insert 522 on the Reader Enquiry Service form for further information. Erba Science (UK) Ltd. Literature Descriptive literature is available concerning the range of equipment for the analysis and control of oil and petroleum products.EDT Research. Insert 523 on the Reader Enquiry Service form for further information. An application report on the use of an electro- chemical sensing system to control accurately the dilution of bulk caustic soda and a flow chart illustrating the electrodeless ,system is entitled “No. 2 : Chemical Concentration Con- trol. ,’ Foxboro‘ Analytical. Insert 524 on the Reader Enquiry Service form for further information. An applications paper describes the “Analysis of Trace and Major Components in Vitamin and Mineral tablets by DC Plasma Emission Spectroscopy,” using the Spectraspan 111. Techmation Ltd. Insert 525 on the Reader Enquiry Service form for further information.A booklet by A. T. Rhys-Williams entitled “Fluorimmunoassay’ ’ reviews various pro- cedures that have been developed. Perkin-Elmer Ltd. Insert 526 on the Reader Enquiry Service form for further information.November, 1980 AD DISTINGUISHED SERVICE AWARD 499 “Scintillation and Radiation Detectors” Cata- Triglyceride I1 enzymatic reagent utilises l o p e No. 126 contains three brochures: glycerol kinase and comes complete with Cali- “Scintillators for the Physical Sciences” (No. brator and buffered diluent. 126P) ; “Crystals and Demountable Assemblies” Bio-Rad Laboratories Ltd. Insert 534 on (No. 126C); and “Scintillators for the Life the Reader Enquiry Service form for further Sciences” (No. 126L). information. Insert 527 on the Reader Enquiry Service form for further information.Nuclear Enterprises Ltd. Application Note 232- 15 describes the gel permeation chromatographic method that is particularly useful for crude oils of high boiling- point (over 500 “C). Hewlett-Packard. Insert 528 on the Reader Enquiry Service form for further information. A booklet describes the uses of Agarose IEF, a supporting matrix for isoelectric focusing. Insert 529 on the Reader Enquiry Service form for further information. Pharmacia (Great Britain) Ltd. A catalogue of selected components for photo- acoustic spectroscopy covers pulsed laser source PAS and CW-continuum source PAS. The list includes sources, choppers, monochromators, beam-splitters, cells and detection electronics. EDT Research. Insert 530 on the Reader Enquiry Service form for further information. About 30 reprints and standard traces are available free of charge, covering micro- elemental analysis, capillary gas chromato- graphy, headspace analysis and detectors. Insert 531 on the Reader Enquiry Service form for further information. Erba Science (UK) Ltd. New Products A modified agarose, called Agarose IEF, for isoelectric focusing exhibits no electroendos- mosis and is non-toxic. An accessory kit and gel slab casting frame are also available. Insert 532 on the Reader Enquiry Service form for further information. Pharmacia (Great Britain) Ltd. The latest addition to the range of endocrine assays, Quantimune Cortisol, is useful for high separation specificity in solid-phase immuno- bead technology. Bio-Rad Laboratories Ltd. Insert 533 on the Reader Enquiry Service form for further information. Analytical Division Distinguished Service Award On the recommendation of its Honours Com- mittee, at its meeting on September 22nd, 1980, the Council conferred the sixth Analytical Division Distinguished Service Award on Dr. Frederick James Bryant formerly of AERE Harwell.

ISSN:0144-557X    

DOI:10.1039/AP9801700494

出版商:RSC    

年代:1980

数据来源: RSC