摘要:

1996 Winter Conference on Plasma Spectrochemistry Fort Lauderdale Florida January 8 - 13 7996 The 1996 Winter Conference on Plasma Spectrochemistry ninth in a series of biennial meetings sponsored by the ICP lnformafion Newsletter features developments in plasma spectrochemical analysis by inductively coupled plasma (ICP) dc plasma (DCP) microwave plasma (MIP) and glow discharge (GDL HCL) sources. The meeting will be held Monday January 8 through Saturday January 13 1996 at the Bonaventure World Conference Center in Fort Lauderdale Florida. Continuing education short courses at introductory and advanced levels will be offered Friday through Sunday January 5 - 7. Spectroscopic instrumentation and accessories will be shown during a three-day exhi bition Objectives and Program The continued growth in popularity of plasma sources for atomization and excitation in atomic spectroscopy and ionization in mass spectrometry and the need to discuss recent developments of these discharges in spectrochemical analysis stimulated the organization of this meeting.The Conference will bring together international scientists experienced in applications instrumentation and theory in an informal setting to examine recent progress in the field. Approximately 500 participants from 25 countries are expected to attend. Approximately 300 papers describing applications fundamentals and instrumental developments with plasma sources are expected to be presented in lecture and poster sessions by more than 200 authors. Symposia organized and chaired by recognized experts will include the following topics 1) Sample introduction and transport phenomena 2) Flow injection spectrochemical analysis 3) Elemental speciation with plasma/chromatographic techniques 4) Plasma instrumentation including chemometrics expert systems on-line analysis software and remote-system automation 5) Sample preparation treatment and automation 6) Excitation mechanisms and plasma phenomena 7) Spectroscopic standards and reference materials 8) Plasma source mass spectrometry 9) Glow discharge atomic and mass spectrometry 10) Applications of stable isotope analyses and 1 1) Laser-assisted plasma spectrometry. Six plenary and 1 8 invited lectures will highlight advances in these areas. Afternoon poster sessions will feature applications automation and new instrumentation. Five panel discussions will address critical development areas in sample introduction instrumentation elemental speciation plasma source mass spectrometry and novel software and hardware directions.Plenary invited and submitted papers will be published in Fall 1996 after peer review as the official Conference proceedings. Schedule of Activities Preliminary Title and 50-Word Abstract Due for Contributed Papers July 3 1995 Exhibitor Booth Reservation and Pre-Registration Deadline September 11 1995 Conference Pre-Registration October 13 1995 Hotel Pre- Reservation October 13 1995 Late Pre-Registration Deadline December 8,1995 1996 Winter Conference Short Courses January 5 - 7,1996 1996 Winter Conference on Plasma Spectrochemistry January 8 - 13,1996 further Information For further information return this form to 1996 Winter Conference on Plasma Spectrochemistry %lCP lnformatlon Newsletter Department of Chemistry Lederle GRC Towers University of Massachusetts Box 3451 0 Amherst MA 01003-4510 USA.AlTN Dr. Ramon Barnes Conference Chairman Telephone (41 3) 545-2294 Telefax (41 3) 545-4490. &- 0 Send further information. 0 I plan to attend accompanied by 0 I plan to present a paper (0 oral 0 poster 0 computer poster). Title 1996 WINTER CONFERENCE ON PLASMA SPECTROCHEMlSTR Y Name Organization Address City Telephone Title State/Cou ntry Telefax Date ZIP/Postal Code EMAlLWhat JAASbase is ... JAASbase i s a unique database of atomic spectrometry reference information containing full bibliographic references to journal articles and conference papers in the field of atomic spectrometry published since 1985.These references are selected by expert atomic spectroscopists who add supplementary information that allows you to search for the references you require. The backfile (covering 1985 to 1994) contains over 28,000 references. Update disks add around another 4,000 references a year JAASbase has been designed to work with the database manager Idealist a fully indexed free-text retrieval system. How will JAASbase help you? If you are an analytical scientist with a need for rapid access to information on techniques used in atomic spectrometry JAASbase is the tool you need. Particularly if you work in an applications laboratory with a restricted budget for primary journals and little or no access to library facilities - JAASbase gives you instant access at your bench. Whether your area of analysis i s food the environment quality control geology metallurgy or whatever JAASbase will quickly become an essential part of your working life.ia 1995 Subscription Price JAASbase Backfile (1 986-94) f 280.00/$490.00 JAASbase Updates 1995 f 99.00/$174.00 Idealist Software f 21 0.00/$368.00 Plus VAT in the UK Available in disk size 3.5" or 5.25" I I THE ROYAL SOCIETY OF To order please contact The Royal Society of Chemistry Turpin Distribution Services Limited Blackhorse Road Letchworth Herts SG6 1 HN United Kingdom. Telephone +44 (0) 1462 672555. Fax +44 (0) 1462 480947. Turpin Distribution Services Limited is wholly owned by The Royal Society of Chemistry. RSC members' should order from The Royal Society of Chemistry Membership Administration Thomas Graham House Science Park Milton Road Cambridge C64 4WF United Kingdom. Telephone +44 (0) 1223 420066. Fax +44 (0) 1223 423623. E-Mail (Internet) RSC1 @RSC.ORG. C H EM I STRY information Services

ISSN:0267-9477    

DOI:10.1039/JA99510BP001

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

EDITORIAL During the 21st FACSS conference in St Louis USA Dr Jim Harnly US Associate Editor of JAAS and Brenda Holliday interviewed Dr Barry Sharp Chairman of the Editorial Board and Judith Egan-Shultler about their memories of the early days of JAAS. Jim Brenda and I decided that on the occasion of the tenth Anniversary it would be very appropriate to interview founding members of the journal. Really you John Ottaway and Judith do constitute the forefathers (and mother) of the journal! I ’ve heard stories about the train trip when you and John Ottaway hatched the idea. Perhaps you could begin by giving us the full story. Barry exactly the start of it but it was the occasion on which the details came into being. The idea goes back to a time when we had the Old Annual Reports on Analytical Atomic Spectroscopy (ARAAS) which was published each year in the form of a book.ARAAS ran for 14 volumes from 1970-1984 following the seminal Sheffield Atomic Absorption Conference of 1968. In the early days ARAAS was highly regarded in that it was an annual summary of what had gone on in the analytical atomic spectrometry literature and it was pretty comprehensive. However as time went on the world changed and people were not so interested in a publication that was looking back over what was effectively sometimes 18 months to 2 years by the time it had gone into print. The demand was for more immediate information and so although a great deal of work went into ARAAS the evidence was that the sales were declining. I was Chairman of the ARAAS Board at the time when the idea of JAAS came about and within the ARAAS organization there had already been some discussions as to whether we shouldn’t change the format and make it into a review journal.I think that the problem was none of us really knew whether there was a market for it. John Ottaway on the other hand had recently joined ARAAS and was still a relatively new boy at that stage but at the same time he was Chairman of the Analytical Editorial Board which ran The Analyst. He foresaw another problem in that there was an increasing number of atomic spectroscopy papers and these were taking up more and more space in The Analyst. It’s a fact in the publishing world that it’s relatively easy to generate papers but more difficult to sell journals and so if you’ve got a major part of your journal growing rapidly but you’re not actually increasing the sales you’re got a problem.John foresaw that contrary to some comments at the time the Well the train trip wasn’t analytical atomic spectrometry literature would continue to grow and since the RSC had always played a part in publishing that work he felt that there was space for a new vehicle for publication. It was on the train journey from St Pancras Station up to Sheffield one night (I can’t remember what we were both doing in London because at that time I lived in Aberdeen and John lived near Glasgow) when John told me about the idea that he felt there was space for another journal. He asked me what I felt about ARAAS joining in and I said that we had considered the journal format and therefore this would be a happy combination.What really took shape on that journey was the concept of JAAS and I think the name (or the suggestion for the name) and the notion that it would be a primary journal with normal review material but it would also incorporate the annual reviews as a major and differentiating feature. Another concern was (and I think it was a very important one) that whereas The Analyst had always been fairly international it was nevertheless perceived as slightly European particularly by the American market and clearly if any analytical atomic spectrometry journal was going to be successful the American market was important. So I think one of the important conclusions we arrived at was that we had to have an editorial base in the US so that US authors could deal with colleagues and peers whom they knew.The rest of the discussions were on technical matters such as how you could actually go from a once every 12 months publication to an every 2 month publication. A lot of ideas were kicked around and subsequently these were put to the Analytical Editorial Board and the ARAAS Editorial Board and both agreed that a new journal was the best way forward. This was certainly a means of keeping the ARAAS principle going and also being able to market it successfully. I suppose from then on we really got into the nitty gritty of it and market surveys were done. Judith I had been aware for some time that something had to be done about the large increase in submissions to The Analyst as I was working as an Assistant Editor at that time on the analytical journals.It was clear that atomic spectrometry was one area where publications were increasing rapidly. However the first I actually heard about the new journal was from John Ottaway who I knew as Chairman of the Analytical Editorial Board. One advantage of having our offices in London was that people would drop in quite often when in town for meetings so we used to see John fairly regularly as he took his duties as Chairman very seriously. Anyway I was ill for a while and John wrote to me telling me to get well quickly as all sorts of exciting things were happening back at the office and it looked as if we were going to have a new journal to work on. At that time this was a major step for the RSC and I know John had to work very hard on his selling job to all the relevant RSC committees but he managed it in the end and by the time I got back to work things were beginning to happen.In fact from then on things had to move pretty quickly as once a decision had been taken plans had to be made to handle the smooth transfer of the ARAAS material to ASU to ensure continuity of coverage. This was no easy task and I think at one point the only people who fully understood the ASU abstracting system were myself Doug Miles Dave Hickman and Barry-it was very complicated! Brenda right from the start on how you were going to promote this new journal? Barry The strategy first involved doing a market survey and this was carried out by the professional staff at the RSC.Basically it was a circular to the analytical atomic spectroscopy community worldwide to ask them if really there was a market. I guess that’s a difficult question because with library budgets shrinking and they were probably even shrinking in those days people were not naturally inclined to vote for a new journal. Nevertheless I think there were enough people out there who saw that perhaps there would be scope for a new specialist journal so when the market report came back it was reasonably positive. I think it was the case that people were quite happy with the concept that there was space in terms of numbers of publications for another journal they were much less happy about having to pay for it or persuade their library committees to put money up for it Judith comprehensive telephone survey to judge peoples opinions.One thing that So was there a strategy then I think they also did a 2 N Journal of Analytical Atomic Spectrometry January 1995 Vol. 10was a key factor as regards obtaining subscribers to this new journal was that we already had a base on which to work the existing ARAAS subscribers whom we hoped would transfer their subscriptions to JAAS. So we were not starting from scratch so to speak. There was also a worldwide network of people who were or had been at some time associated with ARAAS who we hoped would support the journal with primary papers and subscriptions. Also the vision that John had for this journal was of something quite different to anything already out there in the market place not just because it contained the ASU material.He wanted the journal to be called spectrometry not spectroscopy as he considered it to be a measurement technique being carried out by people in thousands of laboratories all around the world as opposed to the more physical aspects of the science being studied by spectroscopists. The journal was intended to be of interest to everyone involved in any area of spectrometry from students to esteemed professors to heads of research laboratories. John wanted JAAS to become part of the atomic spectrometry community and was very keen to develop the News Pages as being a focus for this large family of people who were all friends not just work colleagues meeting up regularly at conferences around the world. Many people have since said to me that they read the News Pages first and thoroughly enjoy them.They have helped show students that their peers are human after all enjoying the social side of conferences given students the opportunity to write conference reports instead of always writing technical reports kept people in touch with how we are all ageing (gracefully we hope) by publishing lots of photographs and many other bits of information of general interest. Through this unique concept for ajournal John was convinced we would have a success on our hands. Jim When during this start up process did you become involved Judith? My understanding from John was that you were hand picked by him to be his editor. Judith I was appointed as Editor in I think the February of 1985 but just to clarify how cautious the RSC were about any new publishing ventures in those days I was only given a temporary upgrading to Editor.I still had to spend some of my time working on The Analyst as it was still considered to be a big risk and no one thought working on JAAS would ever be a full time job little did they know! Eventually after about 18 months they made the job official and I actually had to apply for my own position. I am flattered that you think John hand picked me but although I know he thought I would be the right person for the type of editor he had in mind I have to say that the decision was purely an RSC Management one. John wanted the Editor to become part of the atomic spectrometry community for the people involved in the field to then feel it was their journal and that they were part of it.The Analytical Journals Staff had always attended major analytical conferences but other RSC journal staff did not. John’s idea was to have a higher profile still at conferences and that I should be out and about as much as possible-not an easy thing for the RSC to appreciate at that time as you can imagine. Our major competitor journals all had academic editors who were obviously going to be at all of these meetings so I had to be there too. I was also co-opted on to the Committee of the Atomic Spectroscopy Group of the RSC to ensure that I knew what was going on in the UK and to help them in any way I could. This led to my involvement with BNASS which I always thoroughly enjoyed. Barry I think that is absolutely right.I didn’t know Judith at this stage. I only knew Phil Weston and some of the analytical editorial staff and people in the Books Department who were producing ARAAS. John did know Judith and I think he felt that she was the right person to get the journal up and running. He obviously saw that she had the right qualities that would give us a presence in the market place and of course that turned out to be a very happy and appropriate choice. I can remember even today meeting Judith. I was in a Hall of Residence in Sheffield at the annual ARAAS meeting and this young woman passed on the stairs and I thought ‘Who the hell is that? I don’t think she’s anything to do with us’. Later in the evening John introduced us and I think she must have come to that meeting with some trepidation and perhaps she was a little surprised when she met the analytical spectroscopy community in the UK because they are a fun loving bunch! Judith I can still remember my first ARAAS/ASU meeting too.I arrived knowing only John and handful1 of other people and walked into this large room where the evening was clearly already going with a swing old friends obviously pleased to see each other. Beer and sandwiches were being consumed in vast quantities and I could see only one other woman (Joan Rooke) in the room. What had I let myself in for was all I could think. I have to say that before the evening was out my awe of many of the major workers in the field whose names I had read hundreds of time in the course of editing had been dispelled they were all so friendly and I was soon made to feel welcome and part of the group.I think one of the reasons for this might have been that I gave them an air of respectability in the discos-it certainly helped them having one woman around to dance with. Returning to the office a few days later with sore feet and feeling a lot more relaxed about the prospect of the task ahead of me it rather surprised my colleagues to know which of the well known analytical scientists were the leaders of the expeditions to the discos. Jim Was the RSC enthusiastic in responding to this idea of a new journal. What was the journal turnover response? Was it something to jump at or did you have a sales job on your hands? Barry No there was a definite sales job to be done and really it was John who carried it through. I don’t think the RSC is unenthusiastic about new publishing ventures in fact like most publishers they are keen to spot new openings but rightly so the people who look after the financial side in the Society have to take a cautious approach and it was those people that John had to convince to go along with the launch of JAAS.Fortunately John had great personality and drive and he managed to carry that through and hence we’ve now got JAAS. Brenda A lot of people associate JAAS now with publishing ICP-MS papers. How did that come about? Barry I think it came about because the early workers in the field recognized that this was a new branch of atomic spectroscopy that would be used and developed largely by scientists who had experience in optical atomic spectrometry not mass spectrometry.JAAS was a new journal without a historical affiliation with particular techniques and therefore was an obvious vehicle for publications in new areas such as ICP-MS. Brenda Is this another example ofthe John Ottaway-Judith persuasive combination . . . ? Judith I think we came along at just the right time for ICP-MS and we all benefitted. Alan Date and Alan Gray’s first paper had appeared in the December 1983 issue of The Analyst and we went to great lengths to have their reprints ready for the Winter Conference in Orlando in January 1984? I know Alan Date who was already part of the atomic spectroscopy community really appreciated this as it was such an exciting time for ICP-MS and he wanted to go to Orlando with his published paper in his hand.I think this attitude towards our authors to Journal of Analytical Atomic Spectrometry January 2995 Vol. 10 3 Nput ourselves out whenever we could help them really paid off as they always seemed to support us from then on having seen what a good service we gave. Alan Gray is on the Advisory Board and has always been very supportive of the journal. Early on we also received excellent papers from the people at VG probably because Robert Hutton had been one of John’s PhD students John could be very persuasive. In the course of time we became the obvious journal for ICP-MS papers which was great. Jim age was also certainly through the involvement with the publishing of the Winter Plasma Conference with Ray Barnes and then some of the Winter Plasma Conferences in Europe.My own observation (that the selection of Judith provided a presence for JAAS) is that this is what is distinctly diflerent about JAAS. Would you care to expand on this. Was it intentional. It sounds like John’s idea. Barry also a reflection of the way the RSC operates its journal publications. Most of the commercial publishers when they set up a new publishing venture appoint an Editorial Board and a Chairman of that Board or an Editor who is a major figure in the academic community. That person will normally be paid and will promote the journal both in terms of getting papers and carrying out some of the editorial work of the journal. The RSC doesn’t work that way. The RSC employs professional Editorial Staff who deal with nearly all the editorial and administrative matters. Editorial Boards are appointed to represent the scientific community at which the journal is aimed to advise on matters of policy and to ensure that appropriate standards are maintained.Now there was a departure with JAAS in the sense that we did take on a major name in the academic field your goodself in an editorial role. We still needed a professional editor but John realized that our professional editor would also have to be a public figure in the analytical community. Judith didn’t come from an analytical research background and it was much to her credit that she was able to gain the confidence of the scientific community so that they wanted to do business with her and publish in JAAS. I think that was one of her achievements in her reign as Editor.Judith Not for the first time I must present my credentials for running JAAS! I don’t know what makes you think I did not have an analytical background but after university I worked in an analytical laboratory for I think the new era of coming of It was intentional but it was four years and then on the editorial staff of the Analytical Journals at the RSC for 7-8 years before taking on JAAS. I would have thought that was a reasonable background for the job! Jim M y personal experiences include attending my first CSI where my job was to take you around Judith and introduce you to all thefigures in atomic spectroscopy and you rapidly became friends with many of the people in the area. With the Editor as a publicfigure this constituted a pursuit of papers which was diflerent from the RSC standard a much more abrasive approach.Barry Yes I think JAAS has broken a lot of new ground in the RSC. The RSC is a learned society and has always taken the view that it had high quality journals and if you had a high quality journal then people would automatically publish with you. I guess over the years that has been borne out but I think again John saw correctly that the world was changing and that there would be competition for papers particulary for quality papers especially in the analytical field and we wouldn’t succeed with that very laid back approach. Judith The CSI in Garmisch which Jim just referred to was my first international meeting in my new role and I was fairly apprehensive about the whole trip.John had told me not to worry as he and all his group would be there. What he did not tell me was that they would not arrive until halfway through the week and I had to fight my own battles until they arrived. Jim was extremely helpful and made sure I met lots of people and was not left to eat dinner on my own. However I had not anticipated how anti-JAAS some people were at that time and I really had some very unfortunate discussions with a number of people prior to John’s arrival of course. When John did finally arrive I was in a state of panic wondering what I had got into but he reassured me it would all calm down and be a success in the end which of course it was and these opponents graciously became friends in the end. He then asked me to organize a Board Lunch for about 25 people for the next day.More panic not speaking any German and not knowing where to start. I used my initiative and I think Jim helped too and we had an excellent meeting and lunch for our new Board. This turned out to be the first of many such events at conferences around the world. I soon realized this was John’s way of getting the best out of people encouraging them to do things they did not think they could do but he knew jolly well they could. John had then wanted me to go on to the Graphite Furnace Post-Symposium in Meersburg. However the next week I went to my first FACSS meeting in Philadelphia and I did not at that time want to be away from home for almost three weeks so I came home. I never guessed that eight years later I would be living just 3 km down the road from such a beautiful place as Meersburg and I now realize what a great opportunity I missed back in 1985.Brenda idea of where papers were going to come from? Barry I think initially we thought papers would come from people who’d been involved in ARAAS or publishing in The Analyst a sort of core group that would at least provide the papers for the first two or three issues but we didn’t have in mind any particular subject areas. I think one of the things we were pleasantly surprised to find when we started getting papers was that we were attracting them from across the spectrum (if I can use that word) of analytical atomic spectrometry. Now I am sometimes asked ‘Is this paper suitable for JAAS because it’s too theoretical? The answer to that is clearly ‘No’.Equally people come up to me and say ‘Is this paper suitable for JAAS you only take theoretical papers is it too applied?’ Happily once again the answer is ‘No’. We interpret our remit very liberally and even our atomic remit I think we interpret as liberally as we can. In these days when speciation is so important it is often difficult to define where the boundary between atomic and other spectroscopies lie. Our view is that to define it would be totally wrong and our approach is to look at each paper as it comes in send it to our referees and make a valued judgement as to whether that paper is of interest to our readers. Whether it’s defined as one kind of spectroscopy or another is not important only whether the readers of JAAS and the potential market for JAAS wants to see that information in print is important and if we think that is the case we will take it.Judith We initially used the same typesetter and printer as The Analyst so that if we were ever short of papers for an issue we could ask authors for their permission to transfer their paper from The Analyst to JAAS. We only ever did this with one paper and that was not because we were short of papers but because we felt that paper would be more appropriate in JAAS. The first issue had 15 excellent papers in it but the second was a bit thinner and more of a struggle to get together with 11 papers. After that though we never looked back never being short of papers. The Analyst certainly did not suffer from the appearance of JAAS Did you at the time have an 4N Journal of Analytical Atomic Spectrometry January 1995 Vol. 10either it was almost as if all the publicity and interest in JAAS renewed peoples interest in The Analyst which did not solve the problem of The Analyst getting larger in fact it went from strength to strength.Brenda particular moment that JAAS is now successful? Were you able to say at one Barry I don’t think there was ever a particular moment. After the first year it was fairly clear that we would be successful both in terms of the input of papers and the likely sales which of course were on a reasonable up-slope at that time. Judith In the late summer of the first year John actually came down to London specifically to argue a case for going to eight issues in the second year.He felt already that the journal was here to stay but eight issues would clearly upset the business plan and the RSC needed convincing. We wanted to introduce two dedicated conference issues. We were in negotiation with Ray Barnes for the Winter Conference and it was felt that papers from BNASS would obviously be more appropriate in JAAS than in The Analyst where they had previously appeared. Conference issues were thought to be a good way of getting new authors to try publishing in the journal and we knew that if we gave them a good service they would stick with us. This proved to be an excellent philosophy as it worked particularly with US authors who attended the Winter Conferences. In his inimitable style John won the day but not without a hard battle.The RSC were still being very careful not having launched a new journal for a long time. Fortunately today they are more aware of the changing areas in scientific publishing and are a bit more adventurous but it was a different matter ten years ago. Over the years the conferences we have covered have expanded to include other major international conferences including the CSI this being yet another example of John’s foresight as to what would make a successful journal. Sadly before the year was out I was actually planning another Special Issue for January 1988 dedicated to the memory of John who died suddenly in October 1986 in the first year of publication of the journal he had worked so hard to get into existence. I believe this was the best issue we ever produced it was certainly not an easy thing to do but the final result was excellent.It was then to Les Ebdon’s credit that he took over the reins as Chairman and succeeded in carrying the journal through its initial few years to the great success it is today. Jim Looking back now after 10 years how would you evaluate the success of JAAS? Has it lived up to your expectations or beyond your expectations? Barry primary material it has exceeded our expectations because I suggest that we’ve become one of the two principle journals for spectrometry and analytical atomic spectrometry and I think the quality of our output matches that of any other journal. Also we’ve been fortunate in receiving a very broad spread of papers from across the various subject areas.Another success has been the continuing publication of the ASU Reviews. ARAAS lasted for 14 years and it was a huge amount of work done annually by about 20-30 people on a purely voluntary basis. Nowadays peoples’ working environments are very different to what they were in 1984 and even more so than in 1970 and no-one I know has that sort of spare time anymore. A group of around 30 people still produce these reviews every year and I think it is a great tribute to the ASU Board and to various Chairman who have kept it going. So on the input side we are more than satisfied but if you look at the actual marketing side of the journal then I guess we wouldn’t be so happy. However all journals would like to think they could sell more issues than they are able.I think in terms of the input of Judith Now being married to one of the ASU authors I can categorically say I do not know why these people do it. The time Ian has to spend on writing his section is incredible but he says it is all time well spent as it is an excellent way of keeping up with current literature. I would like now to apologize to all ASU authors for all the telephone calls and hassling I gave them over the years to get their material in on time and for a quick turnround of their proofs. I can see how difficult this is and how dedicated they must be to stick with it! Jim climate towards journals right now is quite dificult. Of course the whole economic Barry launched say even ten years before we could have enjoyed a substantial period of sales growth.Whereas the sales of JAAS are perfectly adequate we’re not in a period when any journal is increasing its sales. We had hoped at the outset to be on a continuing gradual sales up-slope but what we’ve done is to more-or-less reach an equilibrium. Almost every other journal is losing sales and so to stand still is to do well. Exactly. Had the journal been Brenda Two things that have happened very recently are moving to 12 issues which certainly was as a result of the number of papers sent to JAAS and the production of JAASbase. Do you just want to comment on that? Barry I think the move to 12 issues was inevitable because we have had a very healthy supply of papers. There are technical reasons why it is easy to work on a monthly cycle in terms of production of the journal not least the fact that in a monthly cycle if a paper just misses the deadline it is not held back for two months.So if we are looking at lead times to publication 12 issues a year is helpful. The other aspect of 12 issues is that there is a marketing benefit in that a journal which is dropping on your desk monthly is much more in the forefront of your mind than one that comes in two-monthly. If you are thinking of placing work you’re getting that monthly reminder of the presence of the journal in the market place. Moving on to JAASbase. JAASbase as a suggestion has been around once again for quite a long while originating from the Atomic Spectrometry Updates Board. The Board looks at the abstracts that come into the RSC from all over the world and then writes reviews based upon those abstracts and also extracts tabular information which appears in ASU.We’ve done the hard work and all the hours have gone into it so in a sense after that it should be largely a technical issue to get that into a computer format. So we launched JAASbase. I think everyone who has used JAASbase has found it a very useful product to have. Certainly I use it regularly and my research students wouldn’t be without it. Again it finds itself in a fairly competitive world and computer technology changes so quickly that you’re never quite sure whether you’re doing the right thing at the right time. We envisaged JAASbase as a personal product that would be on peoples’ desks on their PCs or on the PCs that they are running their instruments from. We tried to present it in such a way for example making it a floppy disk based system as opposed to a CD-ROM based system so that it is a low cost personal product rather than being in direct competition with the major on-line data base services.Jim People are asking why it wasn’t put on CD-ROM originally. Barry JAASbase was planned three years ago and the computer market place and technology have moved on since then. We may be in a position where we have to review our policy and think whether perhaps we shouldn’t be looking at incorporating abstracts into JAASbase and offering CD-ROM Journal of Analytical Atomic Spectrometry January 1995 Vol. 10 5Nversions. It would increase the price but it may be that we have to think of more imaginative ways of marketing it perhaps offering it at different levels to different end users.This is an area we’ve got to look at because since we’ve had JAASbase for a couple of years we have probably got enough feedback from the users to know what’s good about it and what isn’t good and clearly where we’ve got negative messages we’ll have to do something about it. Jim Another interesting point which was made to me recently was that for archival purposes it would be nice to have JAAS at the end of the year on CD-ROM as a single compilation of the entire year S features. Barry JAAS is available in electronic format through the journals on-line service but that again is another wire service not available as a packaged product to individuals. Now as you say to have a package on CD-ROM would perhaps be the best way of proceeding but it wouldn’t be a simple issue because we have to decide as we did with JAASbase that the support software is going to be to make it readily searchable and addressable.The Royal Society of Chemistry is very interested in electronic publishing and is looking at ways of introducing it in the Society. The major point that we need to get right is a universally accepted format. Judith As a final comment I would just like to say that the years I spent building up and working on JAAS were great. I definitely had to work hard but I got so much out of it too that I have no complaints at all. This was helped by all of the Editorial Boards and of course the great Assistant Editors who have worked on JAAS all of whom had the same enthusiasm as me for the journal.I appreciated the chance to meet so many wonderful people from all around the globe many of whom have become firm friends this big ‘family’ of atomic spectroscopists becoming important in my life. One thing that we have always been keen to do is to involve students as much as possible in this ‘JAAS family’ and it was always encouraging to see people who were doing their PhDs over the years all now having successful careers of their own. The down side of becoming part of such a family is that the loss of someone is felt very deeply. In the past ten years JAAS and I have lost some good friends starting with John then Alan Date Peter Keliher Frans Maessen and last year Dave Hickman and Klaus Dittrich all of whom were supporters of JAAS and examples of the wonderful people I met in the course of my job.I am sorry that my continued involvement did not work out but having put so much of me into JAAS I do hope that the spirit of JAAS which John knew was necessary to its success and which I and the other members of the editorial team over the years worked so hard at lives on. I have a lot to thank JAAS for including meeting my husband incidentally at my first BNASS meeting in 1986 and hence my baby Julian David. I am sure I will still have the chance to meet some of my friends again at conferences and look forward to reading about the second ten years of JAAS in 2006. Barry I would like to echo Judith’s comments. The greatest pleasure that I have derived from being associated with JAAS has been working with the many friends and colleagues who have contributed to its success. Starting with John and then Judith and then Les Ebdon who did much to build on the excellent start that John had made. I should also like to mention friends from the ASU Board Doug Miles the current chairman and then going back further John Davison and Malcolm Cresser who have been with us from the ARAAS days. I suppose my affiliation with JAAS really began in 1973 when I attended my first ARAAS meeting in Sheffield. Sadly as Judith has mentioned we have lost more than our share of friends and colleagues and of course some of the best scientists in our field. I would add the name of Gordon Kirkbright who was a strong supporter of ARAAS and no doubt would have played an important part in the development of JAAS. Nevertheless ours has always been a very open community and we take great pleasure in seeing younger workers coming through and contributing to the JAASIASU organizations. Similarly and inevitably there are changes in the editorial staff and recently we have had the pleasure of working with our new editorial manager Janice Gordon. I do not know what the future is although I am fairly certain that the next decade will see more substantial changes in the world of journal publishing than we have seen perhaps since the start of ARAAS. My hope is that JAAS will continue to serve the analytical atomic spectrometry community and that those who follow derive as much pleasure from their involvement as I have. 6 N Journal of Analytical Atomic Spectrometry January 1995 Vol. 10

ISSN:0267-9477    

DOI:10.1039/JA995100002N

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

Journal of Analytical Atomic Sped romet ry 1llllll! I Ill llllli!lll1llll CONTENTS ~ NEWS PAGES Editorial Janice M. Gordon Editorial Barry Sharp Judith Egan-Shuttler Editorial Doug Miles History of ARMS John Dawson John Price Atomic Spectrometry Viewpoint Scott Tanner European Synchrotron Radiation Facility Freddy Adams Diary of Conferences and Courses Future Issues 1N 2N 6N 7N 9N 12N 13N 14N PAPERS Decrease of Solvent Water Loading in Inductively Coupled Plasma Mass Spectrometry by Using a Membrane Separator Hiroaki Tao Akira Miyazaki Utilization of Metallic Platforms in Electrothermal Vaporization Inductively Coupled Plasma Mass Spectrometry lsam Marawi Lisa K. Olson Jiansheng Wang Joseph A. Caruso Correction of Mass Bias Drift in Inductively Coupled Plasma Mass Spectrometry Measurements of Zinc Isotope Ratios Using Gallium as an Isotope Ratio Internal Standard Raimund Roehl John Gomez Leslie R.Wood house Determination of Rare Earth Elements in Precambrian Sediments at lsua by Inductively Coupled Plasma Mass Spectrometry Tomonori Uchino Mitsuru Ebihara Determination of Arsenic in Environmental and Biological Samples by Flow Injection Inductively Coupled Plasma Mass Spectrometry Meng-Fen H w g Shiuh-Jen Jiang Chorng-Jev Hwang Electrothermal Graphite Furnace Atomic Absorption Signal for Gold in Organic Matrices Shoji Imai Kyoichi Okuhara Toshiyuki Tanaka Yasuhisa Hayashi Kengo Saito Physical Behaviour of Nickel and Copper Modifiers Used in the Determination of Selenium by Electrothermal Atomic Absorption Spectrometry Tariq M.Mahrnood Huancheng Qiao Kenneth W. Jackson Application of Palladium- and Rhodium-plating of the Graphite Furnace in Electrothermal Atomic Absorption Spectrometry Ewa Bulska Wojciech Jedral Automatic Preparation of Milk Dessert Slurries for the Determination of Trace Amounts of Aluminium by Electrothermal Atomic Absorption Spectrometry Marco A. 2. Arruda Mercedes Gallego Miguel Valcarcel Flashlamp Continuum AAS Time Resolved Spectra Helmut Becker-Ross Stefan Florek Reinhard Tischendorf Gisela R. Schmecher CUMULATIVE AUTHOR INDEX INSTRUCTIONS TO AUTHORS COPYRIGHT LICENCE FORM SUBMISSION ON DISK REFEREEING PROCEDURE AND POLICY 1 7 15 25 31 37 43 49 55 61 65 67 74 76 -L 78 AT 0 M I C S P ECT R 0 M E T R Y U P D AT ES References FACSS Announcement and Call for Papers 1R 1 0267 -9477 C 1995 I 1 .1 - 2 Typeset printed and bound by The Charlesworth Group Huddersfield England 01484 517077Journal of Analytical Atomic Sped romet ry 1llllll! I Ill llllli!lll1llll CONTENTS ~ NEWS PAGES Editorial Janice M. Gordon Editorial Barry Sharp Judith Egan-Shuttler Editorial Doug Miles History of ARMS John Dawson John Price Atomic Spectrometry Viewpoint Scott Tanner European Synchrotron Radiation Facility Freddy Adams Diary of Conferences and Courses Future Issues 1N 2N 6N 7N 9N 12N 13N 14N PAPERS Decrease of Solvent Water Loading in Inductively Coupled Plasma Mass Spectrometry by Using a Membrane Separator Hiroaki Tao Akira Miyazaki Utilization of Metallic Platforms in Electrothermal Vaporization Inductively Coupled Plasma Mass Spectrometry lsam Marawi Lisa K.Olson Jiansheng Wang Joseph A. Caruso Correction of Mass Bias Drift in Inductively Coupled Plasma Mass Spectrometry Measurements of Zinc Isotope Ratios Using Gallium as an Isotope Ratio Internal Standard Raimund Roehl John Gomez Leslie R. Wood house Determination of Rare Earth Elements in Precambrian Sediments at lsua by Inductively Coupled Plasma Mass Spectrometry Tomonori Uchino Mitsuru Ebihara Determination of Arsenic in Environmental and Biological Samples by Flow Injection Inductively Coupled Plasma Mass Spectrometry Meng-Fen H w g Shiuh-Jen Jiang Chorng-Jev Hwang Electrothermal Graphite Furnace Atomic Absorption Signal for Gold in Organic Matrices Shoji Imai Kyoichi Okuhara Toshiyuki Tanaka Yasuhisa Hayashi Kengo Saito Physical Behaviour of Nickel and Copper Modifiers Used in the Determination of Selenium by Electrothermal Atomic Absorption Spectrometry Tariq M.Mahrnood Huancheng Qiao Kenneth W. Jackson Application of Palladium- and Rhodium-plating of the Graphite Furnace in Electrothermal Atomic Absorption Spectrometry Ewa Bulska Wojciech Jedral Automatic Preparation of Milk Dessert Slurries for the Determination of Trace Amounts of Aluminium by Electrothermal Atomic Absorption Spectrometry Marco A. 2. Arruda Mercedes Gallego Miguel Valcarcel Flashlamp Continuum AAS Time Resolved Spectra Helmut Becker-Ross Stefan Florek Reinhard Tischendorf Gisela R. Schmecher CUMULATIVE AUTHOR INDEX INSTRUCTIONS TO AUTHORS COPYRIGHT LICENCE FORM SUBMISSION ON DISK REFEREEING PROCEDURE AND POLICY 1 7 15 25 31 37 43 49 55 61 65 67 74 76 -L 78 AT 0 M I C S P ECT R 0 M E T R Y U P D AT ES References FACSS Announcement and Call for Papers 1R 1 0267 -9477 C 1995 I 1 . 1 - 2 Typeset printed and bound by The Charlesworth Group Huddersfield England 01484 517077

ISSN:0267-9477    

DOI:10.1039/JA99510BX003

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

EDITORIAL Atomic spectrometry updates The birth of JAAS and that of Atomic Spectrometry Updates are inextricably linked. When the idea of a new RSC analytical journal was first mooted by Professor John Ottaway in 1983 it was felt that it would be highly desirable to include within it the material which up to then had been published in book form as Annual Reports on Analytical Atomic Spectroscopy (ARAAS). This strategy had the twin merits of differentiating JAAS from most of its competitors by the inclusion of regular authoritative reviews and of reversing a trend of rising costs and declining sales which was beginning to threaten the hardback editions of ARAAS. A combination of primary papers and well targeted reviews was felt to be a winning formula for the new journal- as history has subsequently shown.Elsewhere in this issue John Dawson and John Price tell the story of ARAAS. For 14 years it fulfilled an important need in the atomic spectroscopy community. It was on this sound foundation that Atomic Spectrometry Updates (ASU) was able to build retaining much of the structure philosophy and above all the hard working team of ARAAS. JAAS six comprehensive critical and authoritative annual reviews of both The aim of ASU is to provide within fundamental and applied aspects of analytical atomic spectrometry. The combined scope of the six Updates closely matches that of JAAS. The coverage of individual updates is reviewed from time to time as new techniques or applications come to prominence to ensure that they reflect current trends. For example in 1991 the Updates covering Instrumentation and Atomization and Excitation were reorganized into Atomic Emission Spectrometry and Advances in AAS and AFS and Related Techniques.Currently in addition to these two Updates the structure is Atomic Mass Spectrometry and X-ray Fluorescence Spectrometry 6 N Journal of Analytical Atomic Spectrometry January 1995 Vol. 10Environmental Analysis Industrial Analysis Metals Chemicals and Advanced Materials and Clinical and Biological Materials Foods and Beverages. schedule by a group of authors that operates on its own annual cycle and organizes its work accordingly. The abstracts on which the reviews are based are generated by Board Members themselves although in recent years because of shear pressure of numbers more reliance has had to be placed on authors’ abstracts and those generated by abstracting services such as Analytical Abstracts and Chemical Abstracts.A measure of both the wider coverage and increased workload of ASU is shown by the fact that in 1986 the total number of abstracts was 2039 compared to 4131 in 1993. In addition to papers in the primary literature ASU also includes in its coverage relevant conferences. Although the information contained in many conference abstracts may be limited- and here on behalf of ASU authors I make a plea for a higher information content in abstracts submitted to conferences-the timely publication of Each review is written to a very tight conference programmes via ASU provides an up-to-date picture of current research in a particular field which I know many readers find particularly helpful.The overseas members of the ASU Editorial Board make an especially valuable contribution by being our eyes and ears throughout the world providing proceedings of conferences that are held in their regions and also by covering foreign language journals. For the first ten years of its life all aspects of the ASU organization from abstract generation through collation and dissemination to writing the Updates have depended entirely on the dedicated efforts of the Editorial Board. The scale of the operation is now such that the databasing aspects of it are being transferred to Thomas Graham House. The generation of abstracts and the preparation of the Updates themselves continues to be undertaken by the Board members. Advances in information technology in recent years have opened up great opportunities in scientific publishing.The RSC has recently launched JAASbase which makes available in computer readable form the ASU bibliographic database. Further innovations such as putting the information contained in ASU tables or even the abstracts themselves on CD-ROM are being actively considered. Feedback from many sources over the last decade has shown that ASU plays a significant role in the success of JAAS. I will shortly be vacating the Chair of the ASU Board which I have felt very privileged to occupy for the past six years. Having joined originally as a junior member of the ARAAS organization in 1981 and having served as Review Co-ordinator and subsequently as General Editor I can testify to the enormous dedication camaraderie and sheer hard work of all the members of the ASU Editorial Board and I take this opportunity to pay tribute to them. I look forward confidently to the successful future of ASU under the Chairmanship of Dr Andrew Ellis as I do to the next ten years of JAAS! DOUG MILES Chairman ASU Editorial Board Journal of Analytical Atomic Spectrometry January 1995 Vol. 10 7 N

ISSN:0267-9477    

DOI:10.1039/JA995100006N

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

Utilization of Metallic Platforms in Electrothermal Vaporization Inductively Coupled Plasma Mass Spectrometry* ISAM MARAWI LISA K. OLSON JIANSHENG WANG AND JOSEPH A. CARUSOT Department of Chemistry University of Cincinnati Cincinnati OHI 45221-01 72 USA A method to improve the analytical performance of hydride trapping on Pd inside a graphite furnace and subsequent determination by ICP-MS was investigated. Strips of tungsten tantalum molybdenum and rhenium were coated (electroplated/sputtered) with palladium and used as platforms inside the graphite furnace. A typical pyrolytic graphite-coated graphite platform was also coated with Pd in the same manner for performance comparisons. Scanning electron microscopy (SEM ) and X-ray fluorescence spectrometry were used to characterize the surfaces.SEM showed a smoother Pd layer covering the metallic substrates when compared with the graphite. An analyte signal reproducibility study revealed that Ta Re and Mo were not ideal substrates for this purpose. The As peaks obtained from trapping on the graphite platform were broadened with a decrease in intensity after a few firings. The Pd-sputtered tungsten platform showed superior performance over the other platforms. The linear dynamic range obtained using this platform was improved by one order of magnitude in the upper limit (from 1 to 100 ng ml-') over that reported using a graphite platform in previous work. The limit of detection of arsenic was found to be 0.01 ng rnl-' within the same range obtained from the graphite platform. Keywords Hydride generation; electrothermal vaporization; inductively coupled plasma mass spectrometry; hydride trapping; metallic platforms Continuous hydride generation for sample introduction in analytical atomic spectrometric techniques is a popular method for the detection of arsenic and other volatile hydride-forming elements in environmental samples.'-12 The popularity of this method is due to several advantages that can lead to superior analytical performance over the more common methods of sample introduction such as solution neb~lization.'~-'~ Graphite furnace (GF) trapping of hydrides at relatively low temperatures in the presence of palladium is a potentially useful technique for analyte preconcentration. Lower concen- tration limits of detection for several volatile hydride-forming elements have been obtained by applying this method with electrothermal (graphite furnace) atomic absorption spec- trometry ( ETAAS),17*'8 microwave-induced plasma atomic emission spectrometry ( MIP-AES)19i20 and inductively coupled plasma mass spectrometry (ICP-MS).21 In the last method (ICP-MS detection) micrograms of Pd solution were deposited on a L'vov platform inside the graphite furnace.After drying the Pd solution the hydrides were vented through the furnace at a temperature between 200 and 600°C. At these tempera- tures the palladium trapped the analytes,22 or possibly they were adsorbed on active graphite sites.23924 When the atomiz- ation temperature was reached (2100-2600 "C) the analytes desorbed from the surface and were instantly purged into the *Presented in part at the 1994 Winter Conference on Plasma f To whom correspondence should be addressed.Spectrochemistry San Diego CA USA January 10-15 1994. Journal of Analytical Atomic Spectrometry ICP-MS using a suitable carrier gas (GF carrier gas) such as argon. Preliminary experiments demonstrated the ability to trap and subsequently determine several elements by ICP-MS in a single run,21 and a detailed performance comparison between the trapping method and the typical ETV and the direct HG was presented.21 The collection efficiency of arsine was found to be near 100% at ultra-trace levels (ngl-'). However collection at higher concentrations was limited. This decrease in efficiency limited the method's linear dynamic range and practical applications.In this work Pd-coated metallic platforms (electroplated/ sputtered) were investigated in an attempt to increase the analyte collection efficiency at higher analyte concentrations. The purpose was to examine the utility of a metallic substrate coated with Pd as a platform inside a graphite furnace for arsine trapping. This paper describes the preparation of these metal platforms and presents evidence of palladium coverage on their surfaces. It also discusses in detail the analyte signal reproducibility over an extended number of firings. EXPERIMENTAL Instrumentation Graphite furnace A modified graphite furnace unit (HGA 300; Perkin-Elmer Norwalk CT USA) was used with a graphite tube without the sample introduction hole (Sherba Analytical Lab Products New Port Richey FL USA) for the collection and atomization of the analyte.The Pd-coated platforms (metallic and graphite) were positioned inside the graphite tube in a manner similar to the L'vov platform. A new graphite tube was used with each different platform. Inductively coupled plasma mass spectrometry A VG Plasma Quad PQ I (VG Elemental Winsford Cheshire UK) was used. The detector was operated in the single-ion monitoring (SIM) mode in which the analyte signal can be collected versus time. The optimized operating conditions for this instrument were described in a previous paper.2' Method Hydride generation Reaction of As in acidic solution (4 moll-' HCl) with sodium tetrahydroborate ( 1 % m/m NaBH in 0.1 mol I-' NaOH) was used for the continuous generation of arsine.A two-channel peristaltic pump was used to feed both the analyte and the reagent solutions at the same flow rate (0.45 ml min-') into a polyethylene reaction tube (10 cm x 0.2 cm id.). The gaseous products (arsine and excess hydrogen) were carried by a purging gas (0.7501min-' argon) to the graphite furnace through a polypropylene porous membrane tube which was Journal of Analytical Atomic Spectrometry January 1995 Vol. 10 7utilized as a gas-liquid separator (GLS). The GLS and the instrumental set-up were described in detail previously.21 Preparation of the metallic platforms Electroplating. Tungsten and tantalum foils 1 mm thick (Johnson Matthey Ward Hill MA USA) were cut to similar dimensions as a typical L'vov platform by an electrodischarge machine (EDM) (Lambda Research Cincinnati OH USA).The platform-shaped metallic strips were etched in a hydroflu- oric acid-nitric acid solution for 4 h. This step was necessary to clean the surface to remove cutting process residues. Prior to plating they were rinsed in ethanol and air dried. The electroplating solution was 10%0 Pd metal in 10% nitric acid and a palladium wire 99.9% pure (Johnson Matthey) was used as an anode. The three platforms W Ta and graphite were each electroplated long enough to form a significant layer of Pd on their surfaces. After the plating they were placed inside a graphite furnace and the temperature was ramped to 2650 "C five times. Those platforms will be identified throughout this paper as graphite 1 tungsten 1 and tantalum 1.Sputtering deposition. Tungsten molybdenum tantalum and rhenium strips 0.1 mm thick (H. Cross Weehawken NJ USA) with the dimensions of a typical L'vov platform were used. As purchased the metallic strips had minimal surface roughness. Prior to sputtering the metallic strips were rinsed in ethanol blown dry with nitrogen and immediately placed in the sputter- ing system. The graphite and metallic strips were arranged in a circle on the substrate holder and sputtered in a single experiment at room temperature. A commercially available palladium plate (100 x 100 mm 0.1 mm thick 99.9% pure; Johnson Matthey) was used as a target for the sputtering source. A 1 pm thick film of palladium was deposited on one side of the platforms. The sputtering experiment was performed by the Material Science Department College of Engineering University of Cincinnati.The sputtered graphite tungsten and tantalum platforms are henceforth identified as graphite 2 tungsten 2 and tantalum 2. Directly after deposition (anealing at high temperature was not carried out) palladium surface roughness and coverage were determined by scanning electron microscopy (SEM) and X-ray fluorescence (XRF) spectrometry. Reagents All solutions were prepared with distilled de-ionized water (resistivity 18 mi2 cm) (Barnsted PCS Boston MA USA). Hydrochloric acid ( 12 moll-' Baker Instra-analyzed reagent; J.T. Baker Phillipsburg NJ USA) and nitric acid (70% certified ACS reagent; Fisher Scientific Fairlawn NJ USA) solutions were prepared by dilution with distilled de-ionized water to the desired concentrations.Sodium tetrahydroborate (NaBH,) (99% powder analytical-reagent grade; Johnson Matthey) solution was prepared by dissolving the powder in 0.1 moll-' NaOH (ACS reagent; Fisher Scientific). Arsenic working standard solution was prepared by serial dilution of a 1000 mg ml-' stock standard solution (atomic absorption standard solution; Aldrich Milwaukee WI USA). The pal- ladium electroplating solution (Baker Newark NJ USA) was used without any modification. Sample Drinking water HPS certified reference material lot No. 390225 (High-Purity Standards Charleston SC USA) and Freeze-Dried Urine (low level non-certified standard) Standard Reference Material SRM 2670 (NIST Gaithersburg MD USA) were analysed for arsenic. One volume of the drinking water was mixed with two volumes of 6 mol 1-1 HCl to give a final acid concentration of 4 moll-l.The urine sample was reconstituted in 4mollM1 HCl following NIST instructions. Procedure The arsine was generated continuously and was introduced into the furnace by the GLS carrier gas during the hydride trapping step of the GF temperature programme only; this step was 30 s in duration in all experiments. A four-way valve (Whitey Highland Heights OH USA) was used to control the carrier gas flowing into the graphite furnace. In one position of this valve only the GLS carrier gas is flowing into the graphite furnace whereas in the other position the GF carrier gas only flows in. The GF carrier gas was argon at a flow rate of 130mlmin-'. The GF carrier gas purged the furnace at all times with the exception of the hydride trapping step.The GF carrier gas transfers the analytes during the atomization step to the plasma. A representative GF tempera- ture programme used in this study is presented graphically in Fig. 1. RESULTS AND DISCUSSION Surface Coverage The XRF counts for Pd obtained from the electroplated tungsten 1 tantalum 1 and graphite 1 platforms were 2633 576 and 827 respectively. These counts represented Pd cover- ages of 48% on W and 29% on Ta. Elements with relative atomic mass less than 19 could not be determined using the XRF instrument utilized in this study so the coverage ratio on the graphite platform could not be determined. Fig. 2(a) (b) and (c) are scanning electron photomicrographs of the Pd film electroplated on the graphite tungsten and tantalum substrates respectively. The scanning electron photomicro- graph for the graphite platform presented in Fig.2(u) shows microscopic aggregates of palladium on the surface with vari- able sizes. Presumably the pyrolysed graphite surface had a limited interaction with Pd. The XRF count and the scanning electron photomicrograph obtained from the graphite platform sputtered with Pd (graph- ite 2 ) were similar to those obtained from the electroplated platform. On the other hand all sputtered metallic platforms had better than 95% Pd coverage. Fig. 3(a) (b) and (c) are scanning electron photomicrographs of the Pd film coating the tungsten 2 molybdenum and rhenium substrates respectively. Trapping Reproducibility The reproducibility of the arsine signal obtained by using each platform was evaluated by examining the relative standard 3000 Clean 2 2500 I;' 2000 2 5 1500 \ OI a E 1000 $ 500 20 40 60 80 100 120 140 160 0 Time/s Fig.1 Graphical representation of a prototype graphite furnace temperature programme 8 Journal of Analytical Atomic Spectrometry January 1995 Vol. 10Fig* Scanning photomicrograph of Pd On Fig. 3 Scanning electron photomicrographs of 1 pm thick fih of Pd (a) graphite (b) tungsten and (c) tantalum. For XRF counts and coverage see Surface Coverage sputtered on (a) tungsten (b) molybdenum and (c) rhenium. XRF counts indicated that Pd was covering more than 95% of these surfaces deviation (s,) for several trapping replicates. After seven blank firings the graphite 1 platform was used in eight trapping experiments with 1.35 ng of arsenic.The peak areas obtained for each of these experiments are presented graphically in Fig. 4(u) The s obtained for the eight trappings performed in this study was less than 26%. Following this study a sub- sequent XRF experiment showed no discernible Pd peak and presumably none of the palladium remained on the surface. The results from SEM supported this finding. Fig. 5(a) is a scanning electron photomicrograph of this surface showing only the dull graphite. After three blank firings the graphite 2 platform was used in 27 trapping experiments with 0.7ng of arsenic. The peak areas obtained for each of these experiments are presented in Fig. 6(u). The over-all s calculated for the 27 trappings per- formed in this study was less than 13%.After the 30 firings an XRF experiment was carried out on this platform the results showed that all of the Pd aggregates were evaporated Journal of Analytical Atomic Spectrometry January 1995 Vol. 10 911 t i 8 10 12 14 I cn v) 3 +I 8 150 0 m 5 100 L 2 (b) 50 m 0 10 20 30 40 50 60 70 150 Ic’ e No. of firings Fig.4 Signal reproducibility from trapping 1.35 ng of As on Pd-electroplated platforms (a) graphite 1 (b) tungsten 1 and (c) tanta- lum. Each bar represents the peak area obtained in a signal trapping experiment and the void areas represent blank firings and these results are similar to those obtained with the electroplated platform. The decrease in the arsenic signal [Fig. 4(a)] and the loss of the sharpness of the As peak realized in this study (see Fig.7) agreed with earlier reports about the effect of palladium on trapping experiments.21,22 When palladium was present inside the graphite tube the analyte collection efficiency was high and the analyte peak was sharp; however when the palladium evaporated (supported by the XRF findings) the trapping efficiency was lost and the analyte peak was much broader. The tungsten 1 platform was fired 75 times and 42 firings were trapping experiments with 1.35 ng of arsenic. The results are plotted in Fig.4(b) where the value obtained from each trapping experiment is presented as a bar and the void areas represent a blank firing. The overall (42 trapping runs) s value calculated is less than 52%. The XRF count showed that less than 2% of the surface was still covered with Pd and Fig.5(b) shows the shiny Pd in the grooves of the shattered tungsten surface after the total of 75 firings. The peak areas obtained with both tungsten 1 and tanta- lum 1 and plotted in Fig. 4(b) and (c) decreased within runs. After several blank firings the signal returned to near its original value and repeated the pattern. A possible explanation for the erratic behavior might be sub-surface involvement in the analyte trapping. This phenomenon will have an unpredict- able effect on the volatilization of the analytes. The analyte peak obtained during the cleaning step shown in Fig.7 (the second peak appearing in both tungsten and tantalum plots) may support this argument. Also a substrate thickness of 1 mm might have been a factor in the substrate-palladium annealing process.Consequently much thinner (0.1 mm) plat- Fig. 5 Scanning electron photomicrographs of the electroplated plat- forms after the reproducibility work; (a) graphite 1 (b) tungsten 1 and (c) tantalum 1 forms were utilized in subsequent experiments (sputtered platforms). The tungsten 2 platform was used for 47 trapping experi- ments with 0.7 ng of arsenic. The results obtained are plotted in Fig. 6(b). The over-all (47 runs) s value calculated is less than 12% and the value calculated for the last 35 runs is less than 5%. The XRF count showed that more than 2% Pd coverage remained on this surface and Fig. 8(a) shows one of the Pd aggregates remaining on the tungsten surface after 82 firings.10 Journal of Analytical Atomic Spectrometry January 1995 VoE. 105 9 13 17 21 25 29 1 5 9 13 17 21 25 29 33 37 41 45 49 . 16 18 20 22 24 26 28 30 No. of firings Fig. 6 Signal reproducibility of 0.7 ng of As trapped on Pd-sputtered platforms (a) graphite 2 (b) tungsten 2 and (c) molybdenum Tungsten 1 2oth firing 7+--4 120 140 160 ' l;O IkO li0 '- Ti me/s Tantalum 1 16th firing Graphite 1 13th firing Fig. 7 Time-resolved signals obtained from trapping of 1.35 ng of arsenic using three different platforms Fig. 8 Scanning electron photomicrographs of the sputtered plat- forms after the reproducibility work (a) tungsten 2 (b) molybdenum and (c) rhenium The tantalum 1 platform was used in 60 firings using the same temperature programme as described before and 44 of those firings were trapping experiments with 1.35 ng of arsenic.The results obtained are plotted in Fig. 4(c). The s value obtained for these experiments was less than 31%. Fig. 5(c) shows the post-trapping scanning electron photomicrograph of this platform. It appeared that the tantalum melted inside the graphite tube. Melting of this platform could have been due to tantalum and palladium forming an alloy with a melting-point lower than the atomization temperature. Fig. 9 is a phasephase diagram of the tantalum-palladium metals and indicates that these two metals can form an alloy with several compositions all of which have melting-points lower than 1950 "C. An attempt to trap using the tantalum 2 platform with a modified temperature programme having an atomiz- ation temperature at 1900 "C was not successful.Presumably at this temperature there was insufficient energy to desorb the arsenic. Similar work was carried out using a sputtered molybdenum platform. As molybdenum and palladium form a binary alloy that melts at temperatures higher than 1755°C,25 the atomiz- ation temperature in the temperature programme was adjusted to 1700°C. Thirty firings were performed on this platform using the modified temperature programme; the last 15 of Journal of Analytical Atomic Spectrometry January 1995 VoZ. 10 1 ITantalum (at.-%) 0 10 20 30 40 50 60 70 80 90 100 3200 I I I I I I I t I 3020°C I 70 2800 1 ( a ) - V 2400 1 = Y +- g 2000 Q E 8 1600 L __--- 1920 & 25°C / - t A- I 1 I I I I I I \ J I - 800 ' ' ' 1 0 10 20 30 40 50 60 70 80 90 100 Tantalum (% m/m) Fig.9 Pd-Ta phase diagram (reproduced from ref. 25 with permission) those firings were trapping experiments with 0.7 ng of As. The s value obtained for these experiments was less than 8%. However the arsenic signal observed was spread over three peaks (Fig. lo) and these peaks corresponded to changes in temperature during the temperature programme. Each peak represents some of the arsenic being volatilized off the surface. It appears as if the modification power of the Pd was lost in the presence of molybdenum and any addition of energy (heating) to the system caused some of the arsenic to be evaporated. A possible explanation for this behaviour is that molybdenum is a very reactive metal and is possibly involved in trapping the arsenic.'' Fig.8(b) shows the post-trapping scanning electron photomicrograph; the XRF count revealed approximately 1% of Pd remaining on this surface. The rhenium platform was also used in a similar manner to the other platforms. The temperature programme was also modified for the reasons mentioned above; the atomization temperature utilized was 1600°C. Fig. ll(a) shows the single- ion monitoring of the first trapping experiment performed on this platform. The increase in the background between 50 and 80s on the time scale represents the arsine that was not trapped inside the furnace; moreover the peak height and area realized during the atomization step between 90 and 120s were lower than those obtained using the other platforms. The signal obtained in the second trapping attempt is presented in Fig.11 (b) and clearly indicates very poor trapping efficiency. 400 u) 2 CI 2 : 2 300 C 2 200 0 a + 4- 100 50 6o i 30 40 i a - Lo 2 80 2 70 * 60 50 40 30 20 10 L 0 4- 90 120 150 0 30 60 Time/s Fig. 11 Time-resolved signal from 0.7 ng of As (ASH,) in an attempt to trap it on a fresh Pd-coated rhenium platform; (a) first run (b) second run. The broad peak appearing between 60 and 90 s represents the As which escaped the trapping during the hydride trapping step of the G F temperature programme (Fig. 1) The poor trapping on this surface could be due to the saturation of the surface with the analyte which possibly formed a refractory complex metallic compound with the palladium. An attempt to volatilize the analyte off the surface at a higher temperature resulted in melting of the platform.Fig. 8(c) shows the surface after the two trapping attempts and the XRF count indicated that about 5% Pd remained on this surface. Peak Shape and Intensity The arsenic peak shape obtained when using different platform substrates after several runs is demonstrated in Fig. 7. The peak obtained from graphite 1 after 13 firings is short and wide; this shape is similar to that observed on trapping the analyte on the wall of an old graphite tube. The peaks that resulted from the metallic substrates were sharper. The second peak due to the cleaning step suggested that subsurface collec- tion or a stable compound formation may be taking place with the substrate metal. A comparison of the peak intensities clearly shows the much higher analyte signal obtained from metallic substrates than that obtained using graphite.The low signal intensity obtained from the experiment employing the graphite 1 platform may be due to the loss of the palladium coating which was also suggested by the XRF count. 0 30 60 90 120 150 Tim e/s Fig. 10 Time-resolved signal from 0.7 ng of As (ASH,) trapped on Pd-sputtered Mo platform. The presence of multiple As peaks after the trapping step suggest the reactivity of Mo with As Memory Effect A new tungsten platform freshly electroplated with Pd was used to study the memory effect. The amount of arsenic (70 ng) utilized was sufficient to saturate the platform. The results 72 Journal of Analytical Atomic Spectrometry January 1995 Vol.10I 1,786,063 I Blank Blank Blank Blank Blank Sample 70 ng Arsenic Blank Blank Blank Fig. 12 Arsenic signals obtained during blank firings due to the memory effect obtained are presented in Fig. 12. The bar height represents the response of the detector to the analyte introduced into the plasma. The blank firings on the abscissa indicated that no arsenic was introduced for trapping in these experiments. The peaks obtained from these blank runs are due to a memory effect. Less than 10% of the original analyte signal was obtained in the first blank firing and Fig. 12 shows that the signal returned to the original background level within seven runs. This result was reasonable considering the high analyte concentration used and the sensitivity of the detector (ICP-MS).Analytical Figures of Merit The limit of detection (LOD) was calculated based on LOD = s/m where s is the standard deviation for a minimum of eight background measurements and m is the slope of the calibration graph. A detection limit for arsenic of 0.01 ngml-I was obtained. The precision of the method was determined by measuring the s for a minimum of six replicates of the standard used for the calibration graph. The s values obtained were less than 10 14 and 11% for concentrations of 1 I0 and 100 ngml-I respectively. Fig. 13 shows the log-log plot of the linear dynamic range over the concentrations mentioned above; the slope of this plot is 1.03. Sample Analysis Prelimenary work to test the accuracy of this method was carried out by the determination of the total arsenic concen- 0 1 2 Log [concentration ( p p b ) l Fig.13 Arsenic linear dynamic range in log space obtained from the trapping study tration in HPS drinking water. The result obtained was 60+ 3 ng ml- ' (average k 2s). This result is lower than that expected i.e. 8OkO.4 ng ml-I. A possible explanation for the low values obtained from the samples is a matrix effect on the hydride generation reaction.26-28 High concentrations of sodium calcium and magnesium in this matrix and the pres- ence of several transition metals may have a retarding effect on the efficiency of the hydride generation reaction. CONCLUSION A thin (0.1 mm thick) tungsten strip coated with Pd has the potential to be utilized as a platform inside a graphite furnace. The plasma discharge sputtered platforms showed superior results to the electroplated platforms.The sputtered tungsten platform retained the palladium for an extended number of firings more than 80 in this study. Utilization of this platform increased the palladium surface area available for analyte trapping which improved the linear dynamic range by an order of magnitude. Also in this study the Pd solution depos- ition step was eliminated which could improve the sample throughput and assist in the automation of this technique. However a number of blank firings (12-20) are necessary for conditioning the surface and could include cleaning and proper annealing of the palladium and tungsten. Pd-coated tantalum molybdenum and rhenium were found not to be suitable for this technique possibly owing to the reactivities of these metals at the temperature used (400 "C).I.M. acknowledges the University of Cincinnati's scholarship fund for their support and E. H. Evans for suggesting the problem. The authors thank professor A. T. Hubbard for helpful discussions. This project received partial support by grant No. ES 04908 and ES 03221 from NIEHS. The authors are also grateful to the Material Science Department for assisting with the SEM and XRF studies and particularly Mr. Ernest Clark whose advice and help were invaluable. REFERENCES 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Le X. C. Cullen W. R. and Reimer K. J. Appl. Organomet. Chem. 1992,6 161. Zhang B. Tao K. and Feng J. J. Anal. At. Spectrom. 1992,7 171. Le X. C. Cullen W.R. Reimer K. J. and Brindle I. D. Anal. Chim. Acta 1992 258 307. Ybanez N. Cervera M. L. and Montoro R. Anal. Chim. Acta 1992 258 61. Rohr U. and Meckel L. Fresenius' J. Anal. Chem. 1992,342,370. Cacho J. Ferreira V. and Nerin C. Analyst 1992 117 31. van Elteren J. T. Haselager N. G. Das H. A. de Ligny C. L. and Agterdenbos J. Anal. Chim. Acta 1991 252 89. Alverez G. H. and Stephen S . G. Anal. Lett. 1991 24 1695. Schramel P. and Xu L. Freesius' J. Anal. Chem. 1991 340 41. Tao H. and Miyazaki A. Anal. Sci. 1991 7 55. Ebdon L. Hill S. J. and Jones P. Talanta 1991 38 607. Hakala E. and Pyy L. J . Anal. At. Spectrom. 1992 7 191. Story W. C. and Caruso J. A. in Preconcentration Techniques for Trace Elements ed. Alfassi Z. B. and Wai C. M. CRC Press Boca Raton FL 1992 p.333. Heitkemper D. T. Wolnik K. A. Fricke F. L. and Caruso J. A. in Inductively Coupled Plasma in Analytical Atomic Spectrometry ed. Montaser A. and Golightly D. W. VCH New York 2nd edn. 1992 p. 781. Nakahara T. Prog. Anal. Spectrosc. 1983 6 163. Janghorbani M. and Bill T. G. Anal. Chem. 1989 61 701. Li Z. McIntosh S. Carnirck G. R. and Slavin W. Spectrochim. Acta Part B 1992 47 701. Doidge P. S. Sturman B. T. and Rettberg T. M. J. At. Anal. Spectrom. 1989 4 251. Matusiewicz H. Sturgeon R. E. and Berman S . S. Spectrochim. Acta Part B 1990 45 209. Bulska E. Tschopel P. Broekaert J. A. C. and Tolg G. Anal. Chim. Acta 1993 271 171. Journal of Analytical Atomic Spectrometry January 1995 Vol. 10 1321 Marawi I. Wang J. and Caruso J. A. Anal. Chim. Acta 1994 291 127. 22 Sturgeon R. E. Willie S. N. Sproule G. I. Robinson P. T. and Berman S. S. Spectrochim. Acta Part B 1989 44 667. 23 Lee D. S. Anal. Chem. 1982 54 1682. 24 Sturgeon R. E. Wille S. N. and Berman S. S. J. Anal. At. Spectrom. 1986 1 115. 25 Binary Alloy Phase Diagrams ASM International Materials Park OH 1986. 26 Smith A. E. Analyst 1975 100 300. 27 Yamamoto Y. and Kumamaru T. Fresenius’ 2. Anal. Chem. 1976,281 353. 28 Pierce F. D. and Brown H. R. Anal. Chem. 1976 48 693. Paper 4/01 51 8E Received March 14 1994 Accepted September 13 1994 14 Journal of Analytical Atomic Spectrometry January 1995 VoZ. 10

ISSN:0267-9477    

DOI:10.1039/JA9951000007

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

ATOMIC SPECTROMETRY VIEWPOINT Scott Tanner SCIEX 55 Glencameron Road Thornhill Ontario L3 T 7P2 Canada During Dr Tanner’s (S.T.) attendance at the Fourth Durham Plasma Conference September 11-16 1994. Dr Robert Hutton (R.H.) a member of the JAAS Editorial board and Brenda Holliday (B.H.) Senior Assistant Editor of JAAS interviewed him about his work on inductively coupled plasma mass spectrometry. Scott Tanner and Robert Hutton B.H. the birth of JAAS and we are hoping to run a series of interviews with leading atomic spectroscopists to hear their views on the current scene. Could you just giue me some background as to your education how you came to work in the field and how you ended up working at SCIEX? S.T. and graduate studies at York University in Toronto where I worked with Diethard Bohme and John Goodings on ion-molecule reaction kinetics and flame ion mass spectrometry.The spatial profiles of ions in the flame were interpreted through the dynamics of ion-molecule chemistry to yield a diagnostic for the neutral flame chemistry leading to the formation of soot. After graduation I joined SCIEX ostensibly to start work on a new project combining a high temperature plasma with a mass spectrometer as a new tool for elemental analysis. At that time the plasma was expected to be a microwave-induced plasma. Unfortunately or fortunately I was waylaid for the first few years into developing methods for determining volatile organics in air and mobile organic analyses eventually spending about 4 years working with the EPA to develop methods for rapid on-site dioxin analyses in Missouri and New 1995 is the 10th Anniversary of I took both my undergraduate Jersey.In this work I developed a new type of direct air sampling glow discharge ionization source. It became apparent that the source was sufficiently intense that the ion optics were space-charge-limited and I began developing a model to calculate space charge. At about the same time I began hearing from my colleagues about problems that they were having with what had become an ICP-MS instrument and realized that in fact their space charge problems were considerably more severe than were mine. The space charge model was adapted for the ICP source and so I really came back into the ICP-MS world through the back door of ion optical calculations.Since then I have tried to further understand the nature of space charge with the hope of solving the problem for ICP-MS. SCIEX of course is a spin-off company from the University of Toronto having been founded by Barry French Neil Reid and Adele Buckley of the Institute for Aerospace Studies (UTIAS). We have always had a close relationship with UTIAS. About 6 years ago now the Ontario provinical government introduced a programme known as the Ontario Technology Fund which was intended to improve technology development in Ontario and specifically to improve the relationship between universities and industry. As part of that contract with the government several of the scientists at SCIEX were then seconded to the university. As a result I’ve been working at the university now for the past 6 or 7 years in a little bit more free-form research than might normally be anticipated in industry.With Barry’s recent retirement from the university we may want to re-evaluate how we deal with the university R.H. Does that mean that you will move back to the factory to the plant? S.T. No. Actually SCIEX is building a new plant considerably closer to my house in fact. However I’ll probably still be staying at the university. It is a good environment to work in being less restrained than the factory might be. R.H. Less telephones? S.T. Definitely. At the factory I still get calls about dioxin analyses the details of which I find difficult to remember now. R.H. One of the aspects that is less well known about you is your gymnastics expertise-tell us a little bit about that.S.T. As a youngster I was in a demonstration acrobatics corps and got serious about gymnastics in my teens. I originally chose York University as my school based on their excellence in gymnastics in Canada. Throughout my varsity career we were the national champions. It’s interesting that most of my team-mates were studying the sciences and a surprising number of us went on to graduate school. By 1975 I was with the national team. At various times I was one of the best on Pommel Horse Vault and Parallel Bars. My relatively short fingers meant I had to struggle a bit to stay on the Horizontal Bar and Rings; that was before looped handgrips were in use. At the 1975 Nationals which were the first of the Olympic Team Trials I suffered a rather severe knee injury which put an end to my aspirations for the 1976 Olympic team.R.H. Did you actually think you could get into the Olympics? S.T. Well yes. B.H. So was it ever a choice between gymnastics and chemistry? S.T. Yes well having not succeeded in 1976 the decision now was whether to persist in gymnastics until the 1980 Games or go on to graduate school. Choosing school was probably the best decision I ever made because the 1980 Olympics were cancelled for the West at least because it was held in Russia and that was politically incorrect in those days. My colleagues on the national team I’m afraid forfeited a lot of the rest of their careers for that competition and I feel very bad for them. So I guess in the long run it was a good choice to put school ahead of gymnastics at that time.R.H. S.T. summer for 2 weeks at the Canadian You don’t coach or anything now? Oh I do a bit. I coach every Journal of Analytical Atomic Spectrometry January 1995 Vol. 10 9 NAdventure Camp in northern Ontario. It’s a great camp specializing in waterskiing and gymnastics. My wife and I coach for 5$ hours a day and enjoy the remainder of the days. I was also involved for a long time with the national technical committee for the Canadian Gymnastics Federation acting as national judging chairman for several years. I learned more about politics there than I wanted to and that I am really not suited for politics! R.H. What did you do after that? S.T. Gymnastics gave way to three and a half years of marathon running.That’s where you learn to push yourself hard and work for a long time at intense effort. Guess that comes in handy now in the laboratory! I helped found the Maple Leaf Runners club and coached at marathon clinics. My best time in six marathons was 2:47:13. R.H. Have you sufered any injuries because of it? S.T. Not really. Actually the running is necessary to maintain sufficient muscular development so that my knee doesn’t incapacitate me. It’s probably a sentence for life now. R.H. Have you been running while you’ve been here? S.T. I ran once on Sunday. Yesterday it was too cold and wet and this morning I had no ambition to get out of bed! R.H. Europe. Would you consider yourself a Europhile in any way? S.T. I’d love to consider myself a Europhile but no I’m not.I clearly have an affinity for England and for Germany probably because those are the countries I’ve been in most often. I have yet to see some of the other interesting countries. Maybe with time I’ll have a chance. R.H. You haven’t travelled any more in Europe than just Germany and the UK? S.T. Not other than the Winter Conference in Spain last year. While a gymnast I travelled through Yugoslavia Rumania and Bulgaria but that was 22 years ago now. So no I haven’t had the opportunity to see the others yet. This is a plug. Who wants me to come where?! B.H. Does your acceptance of invitations depend on where SCIEX thinks the the market is? S.T. I would like to think not. Primarily because I’m not a marketing type of person. As much as speaking at all might be perceived as marketing I try and am encouraged to play the technical role instead.You’ve spent quite a lot of time in B.H. I always find it difficult myself to appreciate the role of scientists employed by instrument companies. How do you break down your role into a company man and being a scientist? S.T. I’m afraid that some academics don’t really understand the distinguishing constraints either. We do a fair amount of fundamental science at SCIEX although it is usually framed by a need for product development. I suppose the major constraint of the dual role is which aspects of the science we can freely discuss in public. R.H. either is what departments people work for. I work for marketing. S.T. Much of our marketing is now done by the joint venture Perkin Elmer-SCIEX.From the scientist’s point of view it’s a nice arrangement because we can do the science and product development without having to then go out and support it with the marketing role. Particularly nice is to be relieved of the service role which I used to have to do before the joint venture came around. What a lot of people don’t realize R.H. You’ve been working now with ICP-MS for quite a long time and are considered as a leader but where would you see the future for the technology? S.T. I was afraid you were going to ask that! The future of ICP-MS-well it’s nice to see good equipment becoming available. I’d have to separate the future of ICP-MS into a couple of areas. One is the development of the base instrument itself. A second is the way that we use that instrument and probably the third is what it is going to be replaced by.I’ll start with the first one. The development of the ICP-MS instrument itself is driven by a number of points of view. From the marketing point of view the sensitivity will probably always remain an issue. Whether or not it’s a real issue for doing real life analyses sensitivity remains an important benchmark for the success of an instrument. I would like to see more interest placed in improving ion transmission efficiency and matrix effects primarily because I perceive from my rather naive analytical point of view that if you can solve the matrix effects then you can analyse real samples. The same goes for mass bias. Of course from my experience everything related to space charge can be improved.That’s the short of it. Resolution of isobaric interferences non-spectroscopic interferences all the standard things we’ve been hearing for years that have not yet been solved. I think the solution may have much to do with the way we introduce the sample. Capillary electrophoresis (CE) should become important and it should provide an interesting challenge from the technical point of view. The resolution achievable with CE and the small sample size required should resolve a number of issues. So I’d like to see CE come along. I guess I have to get onto how we’re going to go beyond the ICP-MS. How will we replace the ICP or what will replace ICP-MS? I think that both of those are blue sky. The ICP is an ideal ion source for handling high concentrations of elements because its performance is not substantially affected by the matrix itself. But it has the deficiency that it may be too efficient at ionization and therefore it puts more strain on the mass spectrometer.Gary Hieftje has been saying that we should separate the atomization and the ionization stages; that’s certainly one approach to it. B.H. Would that lead to more complicated instrumentation? S.T. I hope not. My wish is always to go to the simplest configuration possible. We started off very complicated. Mass spectrometers have always been perhaps unnecessarily complicated devices. Primarily this is a result of the history of the development of mass spectrometry. Also some developers have read ion optical books like Harting and Reed and have adopted a large number of ion optical components for their various attributes.I think the idea is to make these things more and more simple from the mechanical-electricaI point of view. The computer can make it appear simple because virtually anything can be autotuned so there may be less incentive to be creative in simplicity. My personal preference would be to not take too much advantage of the computer. I don’t want to use the computer to allow the developer to stop developing simpler systems. It would be best to use the computer to control yet simpler mechanical systems. R.H. Do you think there is still a case for manually controlled instruments-a scientist’s instrument? S.T. Absolutely. Now when you’re an instrument manufacturer your targets have to have a broader application range so we’re looking for more and more automation but the researcher has to have flexibility. He may be able to have that flexibility in the same automated instrument or he may have to build his own.As a researcher I would prefer not to have my computer control the instrument because I want to know exactly what the instrument is doing. A lot of things can be hidden by computer control and can really disrupt the fundamental information that you could be getting from your instrument. 10 N Journal of Analytical Atomic Spectrometry January 1995 Vol. 10R.H. Tanner’s career? S.T. Well last week I got a promotion! I’m now just one step away from that hallowed realm of Principal Scientist which is of course one of my goals. I’m not sure where else I’ll be going.We’ve introduced the ELAN 6000 this week which is kind of a milestone for me. I wonder what the next step will be. Of course we have a number of research programmes in the lab aimed at solving the remaining problems and looking towards the next generation of instrumentation. It really requires good input on what the customers are going to want in the next round. I had thought of leaving ICP and getting into alternate ionization sources or maybe even moving into other types of analyses. I think however that for the time being the future holds continued involvement in ICP-MS. It’s also quite exciting as we start promoting the ELAN 6000 and I confess that there is some personal pride involved in that as well so it’s an opportunity to cash in a bit on some prior work.R.H. Is this where you become a marketing person? S.T. I suppose so yes. R.H. So overall Scott Tanner will stay in ICP-MS for the foreseeable future? S.T. I think I’ll stay in ICP-MS. I would also like to simultaneously branch out and do some weird things unspecified weird things at the moment. R.H. Do you think you have the flexibility within SCIEX to do that? S.T. Actually yes we do. We’re pretty fortunate in having a fairly generous perception of what R&D should be doing at SCIEX. We are given a mandate to proceed along certain lines but we’re also given the flexibility to ‘blue sky’ things significantly. And as they say evenings and weekends are still available! B.H. that SCIEX has to spend on research? You were talking about ‘blue sky’ stuf S.T.The Ontario Technology Fund really facilitated that because after the contributions from the joint venture were included with the Ontario Government contribution there was a substantial investment made in research development and engineering. One of the objectives of that was to make SCIEX sufficiently successful that it could maintain that sort of funding on its own. That is now becoming a reality so financing the research has not yet been a concern. WhatS the next step for Scott What about the amount of money R.H. Does this mean that you wouldn’t consider going back to university as a full time academic? S.T. No. That’s been seriously considered over the last while. My most recent thinking on that is to determine what the potential gains of an academic position are.I think given the flexibility of my current position both the flexibility that SCIEX provides and the flexibility that working at the University of Toronto provides that there’s probably not a lot to be gained by becoming a professor. In fact there is a lot to be lost in that now I don’t have to worry about my funding and as a professor that would probably be my primary concern. So I think that someday I might consider something other than SCIEX but not right now. R.H. Do you foresee a situation arising where you could hold a position at SCIEX and a position at University? S.T. That has come up; in fact last week was the last time that it came up. I suspect that there is a chance that we might make an arrangement for an adjunct professorship or something.It might be an attractive option although I think that taking an adjunct professorship probably simply adds to the workload! Nonetheless it might be an opportunity to fulfill ambitions in both directions. B.H. teaching? S.T. It usually does but I’m not sure. I guess that I would have to say that it might be desirable at some point to have an adjunct professorship even if it just helps to decide what I’d really like to do. B.H. the moment about the lack of the number of people taking pure science chemistry or physics the numbers are falling away badly. Is this the same in Canada? What can working scientists do? Can they contribute to halt the trend? S.T. Well that’s a little outside of my experience in Canada. But I can say that there is a lot concern about losing scientists from Canada after graduation primarily to the United States.There’s been a vigorous effort on the part of the Natural Sciences and Engineering Research Council in Canada to encourage Canadian scientists to stay in Canada which is actually how I ended up at SCIEX. NSERC offers an Industrial Research Fellowship which sponsors recent research graduates in industry for a period of up to five years. It certainly makes it easier for small industries to get some research strength and it also encourages those scientists to stay in Canada. It’s also why NSERC encourages industry- Would that involve you in any There’s a concern in Britain at academic relationships. While the students are coming through the university system they are exposed to the industrial environment to show that there is in fact some high technology industry in Canada.As for the students I can’t say that I’ve seen any evidence of a decrease in attendance in technical studies. In fact if anything I’d say that there’s been an increase. Though I might say that from my old school perception perhaps I would like to see more emphasis placed on fundamental science rather than the applications of science. B.H. Well I think that all three of us would say that science has been good to us and we have enjoyed being scientists. How can you get this message across to young people? S.T. money and job satisfaction. I’ve got to admit that job satisfaction is much more important to me than financial gain so long as my boss doesn’t hear that! R.H. I think that we also have a situation in the UK whereby insecurity in the science profession may be brought up because of the recession like pressures and people don’t want to move into the sort of area where they don’t know what will happen.I don’t know if there’s a secure job or even a place for a scientist. S.T. Basically if you aren’t conversant in the sciences and the technologies then you just aren’t going to fare well in the future. You just won’t be a participant in the future without a technological base you’ll be a bystander. B.H. There are more attractive sciences that they want to go into. People are moving into computer work because it is seen as generating lots of money and they are not moving into the fundamental science field because it’s not seen as doing that well. S.T.into biotechnology which is a fascinating field. But it takes an enormous amount of effort to get to the point where you can be a developer in that field. R.H. Canadian national. Is this a reasonable observation? S.T. Yes I’m a big fan of Canada so much so that I think consideration of long term tenure elsewhere would be difficult. You must be commenting on the election in Quebec a couple of days ago. I’ve not yet heard the results though I’m certain that the separatists won. Yet it is my expectation that Quebec will remain within Canada. I’d be incredibly disappointed in a break It’s a trade-off between lots of There is an obvious movement You come across as afiercely Journal of Analytical Atomic Spectrometry January 1995 VoE. 10 11 Nup of the country which is what separatism in Quebec would eventually lead to.There are too many ramifications for our way of life that deserves to be maintained and Quebec does not stand to gain from separating. It really is a wonderful place; we have a good mix of cultures a little of Europe everywhere in Canada. R.H. to split up. I think it’s beautiful. Quebec City is so much like Paris very old and full of history. S.T. Quebec is a great city; highly recommended to visit. There was a I can see why the Quebecois want referendum several years ago on the constitution of Canada. The objective of the referendum was to bring Quebec into the constitution and to bring the remaining provinces into agreement. One clause that was proposed for the constitution recognized the distinct status of Quebec. I gather that it was that clause which eventually caused the referendum to fail. Where we stand now is that we don’t have a completed constitution for Canada and there may be some mistrust between English- speaking and French-speaking Canadians as a result of the referendum and the ensuing discussions. God knows we have to work out these differences in order to save our larger distinctly Canadian society. At this point actually the tape ran out and we realized that we were late for the start of the next session. This is roughly how we ended . . . R.H. Look the afternoon session’s already started and I wanted to catch JoaquinS talk. S.T. Right and so do 1. Thanks Brenda for the lunch and for the opportunity to talk. And thanks to you Robert for taking it easy on me! B.H. And thanks to you both. 12N Journal of Analytical Atomic Spectrometry January 1995 Vd. 10

ISSN:0267-9477    

DOI:10.1039/JA995100009N

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

~ - _ _ _ _ _ _ ~ ~ ~ ~ Opening ceremony of the European Synchrotron Radiation Facility (ESRF) The ESRF situated in the beautiful mountain setting of Grenoble. (Photograph reproduced with permission from Artechnique Seyssem France) On September 30 1994 the official inauguration ceremony of the European Synchrotron Radiation facility (ESRF) took place in Grenoble France. The ESRF is presently the world’s most powerful dedicated storage ring for applications of synchrotron radiation. A number of representatives of the 12 European participating countries and many scientists and science administrators attended this short but festive official ceremony. There were official speeches by the French Minister of Higher Education and Research the mayor of the city of Grenoble and the President of the ESRF council and its Director-General followed by a banquet. The highlight of the inauguration event was a guided tour of the remarkable installation itself the impressive-looking storage ring (with a circumference of 844 m) and the many experimental set- ups some ready and now routinely available to outside users some in development or in the planning stage.The event took place in the spacious experimental hall where bikes are used by the busy staff to move from one location to the other. The European synchrotron is a remarkable achievement with a history going back to 1977 when a first report arguing the need to build a European high energy storage ring appeared. This led eventually to an agreement which was signed at the end of 1988 by 11 European countries (Belgium Denmark Finland France Italy Germany Great Britain Norway Spain Sweden and Switzerland) with a 12th country (Holland) becoming associated in 1990.The Society ESRF was created in 1989 and work on the 6 GeV linear accelerator and the storage ring started in 1990. The first electrons were injected in early 1992 and from 1993 onwards selected experiments were possible within the installation. The first official external users have been running their experiments since the beginning of September 1994. ESRF now employs about 400 people. They worked hard and efficiently to have the machine ready in time and within budget and with specifications far exceeding the original design parameters. From 1995 onwards a total of 5000 hours of machine time will be available to outside users (6000 in 1996) on an expanding number of beamlines.The ESRF staff will eventually build 30 ‘public beamlines’ all making full use of insertion devices (undulators and wigglers). Each beamline is adjusted for use with one or more specific methodologies. Individual outside ‘collaborative research groups CRG will be able to build about 10 additional beamlines using the radiation of the bending magnets of the storage ring. Seven public beamlines and 3 CRGs are presently operational (September 1994). The ESRF is the first of the third generation synchrotron sources and will be a unique research tool until the 7 GeV Advanced Photon Source (APS) in Argonne National Laboratories (near Chicago) and the 8 GeV Spring-8 in Harima Science Garden City (near Tokyo) become operational.The third 12N Journal of Analytical Atomic Spectrometry January 1995 Vol. 10generation synchrotrons are very general tools for basic and applied research with applications in physics (e.g. solid-state physics and spectroscopy) crystallography molecular biology medicine material science etc. They are characterized by the high brilliance and unique polarization properties in a continuous spectrum ranging from the mm region to the gamma-ray regime in extremely short pulses (50 ps) and at high stability. The ESRF is a unique tool for analytical chemistry and chemical analysis. Beamline 24 will be designed for microscopical X-ray fluorescence analysis (see K. Janssens et al. JAAS 9 1994 9 151) with possibilities to perform sub-microscopical mapping of the elemental composition and speciation ability by performing analysis in the near absorption edge region of particular elements. Beamline 23 will be devoted to X-ray fluorescence excitation spectroscopy on ultra-dilute systems. Both beamlines are in the design phase. Beamline 11 will be devoted to nuclear resonance and Mossbauer scattering. Several other public and CRG beamlines will enable X-ray absorption spectrometry for the study of local structure and the chemical environment around selected atoms. Surface and interface analysis and characterization will be possible on several other beamlines. FREDDY ADAMS Universiteitsplein-1 B-2610 Antwerpen Wilrijk Belgium Journal of Analytical Atomic Spectrometry January 1995 Vol. 10 13N

ISSN:0267-9477    

DOI:10.1039/JA995100012N

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

DIARY OF CONFERENCES AND COURSES 1995 Pittcon ’95 The Pittsburgh Conferel- on Analytical Chemistry and Applied Spectroscopy March 5-10 New Orleans Louisiana USA Details can be found in J. Anal. At. Spectrom. 1994 9 49N. For further information contact The Pittsburgh Conference 300 Penn Center Boulevard Suite 332 Pittsburgh PA 15235-5503 USA. Telephone (412) 825-3220; toll free (800) 825-3221; fax (412) 825-3224. Fourth International Conference on Pro- gress in Analytical Chemistry in the Steel and Metals Industry May 16-18 Jean Monnet Building Luxembourg Details can be found in J. Anal. At. Spectrom. 1994 9 50N. For details of providing a contribution to the programme or other information contact CEC/CETAS Conference R. Jowitt British Steel plc Technical Teesside Laboratories PO Box 11 Grangetown Middlesbrough Cleveland TS6 6UB.Telephone + 44 642 467144; fax +44 642 460321 43rd ASMS Conference on Mass Spec- trometry and Allied Topics May 21-25 Atlanta GA USA For further details contact ASMS 1201 Don Diego Avenue Santa Fe NM 87501 USA. Telephone 505 989 4517. Fax 505 989 1073. 5th Annual Flow Injection Atomic Spec- troscopy Short Course June 6-8 Amherst Massachusetts USA Details can be found in J . Anal. At. Spectrom. 1994,9 68N. For further information contact Julian F. Tyson Department of Chemistry Lederle GRC Tower University of Massachusetts Box 34510 Amherst MA 01003-4510 USA. Telephone (413) 545 0195; fax (413) 545 4846. SAC 95 Hull UK The Analytical Division of the Royal Society of Chemistry is to hold SAC 95 an International Symposium on Ana- lytical Chemistry at the University of Hull.The symposium and meeting will be based in the Middleton Hall of the University. The Analytical Division holds annu- ally a Research and Development Topics Meeting for postgraduate research work- ers and younger workers in industry and the public services. In 1995 this meeting will be held at the University of Hull as the first part of SAC 95 on Monday July 10th and on the morning of Tuesday July 11th. The meeting nor- mally contains 12-16 oral presentations and about 100 poster presentations and is a popular medium for encouraging younger workers to present their results to a wider audience. The main scientific programme will be organized around plenary invited and contributed papers covering the whole field of analytical chemistry.The targeted areas will include Chiral recognition; Analytical biotechnology; Sensors; Chemometrics; Process analysis; Quality; Workplace monitoring; Legislative requirements; Sampling and sample preparation; Microwave heating; Developments in atomic and molecular spectrometry including ICP-MS and X-ray tech- niques; Capillary electrophoresis; En- vironmental monitoring; Field analysis; Imaging techniques; Hyphenated tech- niques; Sensory analysis; Structure analysis; and Microspectroscopy. Each subject will be introduced by a plenary or invited lecturer supported by original presentations. In some instances update courses or workshops (demonstration of July 9-15 novel equipment or software) will also be included. Where relevant the interdis- ciplinary nature of the work will be emphasised.For further information contact the Secretary Analytical Division The Royal Society of Chemistry Burlington House Piccadilly London W 1V OBN UK. Vth COMTOX Symposium on Toxi- cology and Clinical Chemistry of Metals July 10-13 University of British Columbia Van- couver British Columbia Canada Details can be found in J. Anal. At. Spectrom. 1994 9 26N. Colloquium Spectroscopicum Inter- nationale (CSI) XXIX August 27-September 1 Leipzig Germany Details can be found in J. Anal. At. Spectrom. 1993 8 50N. Colloquium Spectroscopicum Interna- tionale (CSI) XXIX Post Symposium September 1-4 WernigerodelHartz Germany Details can be found in J. Anal. At. Spectrom. 1994 9 46N. ICP-MS Euroanalysis IX September 1-7 Bologna Italy The venue of this Conference will be the ‘Palazzo della Cultura e dei Congressi’ located in the Exhibition and Fair area of Bologna.The conference will aim to cover all branches of Analytical Chemistry with emphasis on the ‘prob- lem solving’ role of the Discipline. The Scientific programme will consist of invited lectures and contributed papers (oral and posters). In order to ensure high scientific quality all contributed Journal of Analytical Atomic Spectrometry January 1995 Vol. 10 13Npapers will be refereed by an inter- national panel. Further information is available from Professor Luigia Sabbatini Euroanalysis IX Dipartimento di Chimica Universita di Bari Via Orabona 4,70126 Bari Italy. 8th International Conference on Coal Science September 10-15 Instituto Nacional del Carbon CSIC Apartado 73 33080 Oviedo Spain Details can be found in J.Anal. At. Spectrom. 1994 9 61N. For further details contact Dr. Juan M. D. Tascon 8th ICCS Scientific Programme Chairman Instituto Nacional del Carbon CSIC Apartado 73 33080 Oviedo Spain. Telephone + 34.8.528.08.00. Fax +34.8.529.76.62. International Symposium on Environ- mental Biomonitoring and Specimen Banking December 17-22 Honolulu Hawaii USA Details can be found in J. Anal. At. Spectrom. 1994 9 59N. For further information contact K. S. Subramanian Environmental Health Directorate Health Canada Tunney's Pasture Ottawa Ontario K1A OL2 Canada (phone 613-957-1874; fax 613-941-4545) or G. V. Iyengar Center for Analytical Chemistry Room 235 B 125 National Institute of Standards and Technology Gaithersburg MD 20899 USA (phone 301-975-6284; fax 301-921-9847) or M.Morita Division of Chemistry and Physics National Institute for Environmental Studies Japan Environmental Agency Yatabe- Machi Tsukuba Ibaraki 305 Japan (phone 81-298-51-6111 ext. 260; fax 8 1-298-56-4678). Sixth Surrey Conference on Plasma Source Spectrometry September 17-20 Jersey UK For further details contact Dr K. Jarvis NERC ICP-MS Facility Centre for Analytical Res. in the Environment (CARE) Imperial College at Silwood Park Buckhurst Road Ascot Berkshire SL57TE UK. Telephone +44(0) 344 294517; fax +44(0) 344 873997. 1996 1996 Winter Conference on Plasma Spectrochemistry January 8-13 Fort Lauderdale Florida USA Details can be found in J. Anal. At.Spectrom. 1994 9 53N. For further information contact Dr R. Barnes ICP Information Newsletter Department of Chemistry Lederle GRC Towers University of Massachusetts Box 34510 Amherst MA 01003-4510 USA. Telephone (413) 545 2294; telefax (413) 545 4490. International Schools and Conferences on X-Ray Analytical Methods January 18-25 Sydney Australia Details can be found in J . Anal. At. Spectrom. 1994 9,47N. For further information contact AXAA '96 Secretariat GPO Box 128 Sydney NSW 2001 Australia. Telephone 61 2 262 2277. Fax 61 2 262 2323. Telex AA 17651 1 TRHOST. Analytica Conference 96 April 23-26 Munich Germany Details can be found in J. Anal. At. Spectrom. 1994 2 69N. For further information contact Messe Munchen GmbH Messegelande D-80325 Munchen Germany. Tele- phone +49 89 51 07-0; telex 5 212 086 ameg d; fax +49 89 51 07-177. 14 N Journal of Analytical Atomic Spectrometry January 1995 Vol. 10

ISSN:0267-9477    

DOI:10.1039/JA995100013N

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

FUTURE ISSUES WILL INCLUDE- Optimization of Operating Conditions for Precise Measurement of Zirconium and Hafnium Isotope Ratios by Induc- tively Coupled Plasma Mass Spec- trometry (ICP-MS)-Qianli Xie and R. Kerrich Solid Sampling Electrothermal Vaporiza- tion Inductively Coupled Plasma Mass Spectrometry for the Determination of Arsenic in Standard Reference Materials of Plant Origin-Frank Vanhaecke Sylvie Boonen Luc Moens and Richard Dams Laser Ablation Sampling with Indus- tively Coupled Plasma Atomic Emission Spectrometry for the Analysis of Proto- typic Glasses-Richard E. RUSSO W. T. Chan M. F. Bryant and W. F. Kinard Trace Enrichment and Determination of Gold by Flow Injection Inductively Coupled Plasma Spectrometry Part 11. Inductively Coupled Plasma Mass Spec- trometry-M. Gomez and Cameron W.McLeod Continuous Hydride Generation Low Pressure Microwave Induced Plasma Atomic Emission Spectrometry for the Determination of Arsenic Antimony and Selenium-Florian Lunzer Rosario Per- eiro-Garcia Nerea Bordel-Garcia and Alfred0 Sanz-Medel Interference-Free Determination of Sel- enium@) at Environmental Levels by Capillary Gas Chromatography Micro- wave Induced Plasma Atomic Emission Spectrometry after Volatilization with Sodium Tetraethylborate-M. B. de la Calle Guntinas Ryszard Lobinski and Freddy C. Adams Spectrometer System for Simultaneous Multi-element Electrothermal Atomiza- tion Atomic Absorption Spectroscopy Using Line Sources and Zeeman Effect Background Correction-Bernard Rad- ziuk G. Rodel H. Stenz H. Becker-Ross and S. Florek Determination of Organometallic Species by Gas Chromatography Induc- tively Coupled Plasma Mass Spec- trometry-Andreas Prange and Jantzen Eckard Determination of Beryllium in Drinking and Waste Water by Tungsten-Furnace Atomic Absorption Spectrometry- Tomas Cernohorsky and Stan Kotrly Direct Determination of Samarium Neodymium Ratio in Geological Mate- rials by ICP-Quadrupole Mass Spec- trometry with Cryogenic Desolva- tion Comparison with Isotope Dilution Thermal Ionization Mass Spectrometry -Christian Pin and Philippe Telouk 14 N Journal of Analytical Atomic Spectrometry January 1995 Vol. 10

ISSN:0267-9477    

DOI:10.1039/JA995100014N

出版商:RSC    

年代:1995

数据来源: RSC

摘要:

Correction of Mass Bias Drift in Inductively Coupled Plasma Mass Spectrometry Measurements of Zinc Isotope Ratios Using Gallium as an Isotope Ratio Internal Standard* RAIMUND ROEHL AND JOHN GOMEZ California Public Health Foundation 2151 Berkeley Way Berkeley CA 94704 USA LESLIE R. WOODHOUSE Department of Nutritional Sciences University of California at Berkeley Berkeley CA 94720 USA Gallium was used as an isotope ratio internal standard to correct the mass-bias drift of an inductively coupled plasma mass spectrometer employed for zinc isotope ratio determinations. The Zn isotope ratios were measured to establish dietary Zn absorption in nutritional studies using 67Zn aZn and "Zn as tracers and &Zn as the reference isotope. Natural abundance Zn standards were analysed before and after each group of five samples.All samples and standards were adjusted to a common Zn concentration and spiked with Ga to obtain a 69Ga intensity roughly equal to that of &Zn. The measured 7'Ga:69Ga ratios served to monitor and correct for changes of the instrumental mass bias. Adding the two Ga isotopes to the data acquisition programme increased the cycle time of the mass spectrometer by only 25% and had no discernible effect on the precision of individual Zn isotope ratio determinations. Three different methods for correcting the measured Zn isotope ratios for mass-bias drift were compared (i) simple division of the Zn isotope ratios by the Ga isotope ratios; (ii) correction based on a power law; and (iii) correction by a regressien method which uses the relationships between the temporal changes of the 71Ga 69Ga ratio and the three Zn isotope ratios for each analytical batch.The correction based on regression consistently gave the best results because it avoided undercorrection or overcorrection of mass-bias drift; even when there was little or no correlation between the drift of the Zn and Ga isotope ratios the range of variation of the corrected data was not increased. On the average the regression correction method reduced the drift of the Zn isotope ratios by a factor of 2.5. The study included the derivation of equations which can be used to predict the achievable improvement in precision for the simple division and regression correction methods directly from the measured data i.e. without actually applying the corrections.Keywords Isotope ratio internal standard; inductively coupled plasma mass spectrometry; mass bias drift correction; gallium; zinc Inductively coupled plasma mass spectrometry (ICP-MS) con- tinues to gain importance in biological and nutritional studies using isotope tracers. The attractive features of ICP-MS are its applicability to almost all elements of the Periodic Table and its excellent sensitivity high sample throughput and ability * Presented at the 1994 Winter Conference on Plasma Spectrochemistry San Diego CA USA January 10-15 1994. I Journal of I Analytical I Atomic Spectrometry to determine isotope ratios with a good degree of short-term precision. Over the past two years the present authors have collabor- ated on studies of human Zn metabolism using 67Zn 68Zn and 70Zn tracers with 66Zn as the reference isotope.'-3 The samples analysed included purified extracts of human blood plasma urine and faecal material.Because of the large number of specimens ICP-MS is better suited for the isotope ratio measurements than thermal ionization mass spectrometry (TIM S). One limitation of isotope ratio determinations by ICP-MS with quadrupole instruments is that the measured ratios are subject to a small amount of mass bias (discrimination). This means that the observed isotope ratios differ slightly from those generally accepted for a given element; the relative differences of observed and accepted values typically range from 0 to 5%. The mass bias observed in ICP-MS can change with time due to variations in instrument conditions.Although the mass bias itself and its drift can partially be monitored and corrected for by frequently analysing solutions containing Zn isotopes at natural i.e. known abundances this approach does not provide a correction for each individual sample. Correction schemes which are based solely on analyses of natural abundance standards usually require the assumption that the mass-bias drift is linear with respect to time between analyses of the standards. Since the correction calculations in this case also demand considerable operator involvement e.g. manual parsing of the data the linear interpolation method was not evaluated in this study. A more direct approach to the correction of mass-dependent drift has been suggested by Longerich et u L ~ who added TI as an internal standard element with a constant isotope ratio to samples that were analysed for Pb isotopes.Changes in the observed T1 isotope ratio were used to correct the readings for the Pb isotopes for each individual sample. The correction equations were based on a power law designed to account for the mass difference of the isotopes forming a given ratio. A detailed evaluation of that method has been published by Ketterer et al.' Amarasiriwardena et aL6 reported the use of Ga to monitor changing ICP-MS response factors for Zn isotopes. However those workers did not correct the "Zn 68Zn ratios measured in their study based on the observed 71Ga 69Ga ratios 'since small variations in these two isotope ratios are not always correlated'.The Ga isotope ratios merely served to indicate the presence of excessive drift or noise and the need for instrument maintenance. The purpose of the present study was to demonstrate that Journal of Analytical Atomic Spectrometry January 1995 Vol. 10 15Ga can be used effectively as an isotope ratio internal standard (IRIS) to correct for mass-bias drift in Zn isotope ratio measurements by ICP-MS. Gallium is an almost ideal IRIS for Zn isotope ratio measurements because it is a rare element with a mass close to that of Zn. It has two isotopes of comparable abundance 69Ga and 71Ga neither of which suffers elemental isobaric interferences from singly charged ions (Fig. 1). One possible drawback of Ga is that its ionization potential of 6.00 eV is quite different from that of Zn (9.39 eV).This means that Ga and Zn may respond differently to changes in plasma conditions; however this should not affect the isotope ratios of the two elements. Potential interferences in the determination of the Zn isotopes from singly charged species or in the determination of either Zn or Ga from doubly charged ions of Bay La Ce and Pr can be avoided by appropriate sample clean-up procedures (cf. under Experiment a1 ). To implement the gallium IRIS method natural abundance Zn standards were analysed before and after each group of five samples. The Zn isotopes 67Zn 68Zn and 70Zn served as tracers in the nutritional studies and 66Zn was employed as the reference isotope. All samples and standards were adjusted to a common Zn concentration of 250 or 500 pg 1-' and spiked with Ga to obtain a 69Ga intensity roughly equal to that of 66Zn.Use of the more abundant 64Zn as the reference isotope would have limited the total Zn concentration to a lower level (to avoid detector shutdown for 64Zn) and resulted in lower count rates for the least abundant 70Zn isotope. Concentration levels of both elements were selected to maintain count rates with an ultrasonic nebulizer which yielded average isotope ratios with standard errors of the mean of <0.17% (corre- sponding to relative standard deviations (RSDs) of <0.5% for ten replicate measurements). Four isotope ratios 67Zn 66Zn 68Zn 66Zn 70Zn 66Zn and 71Ga 69Ga were measured for each sample or standard. Changes in the 71Ga 69Ga ratio were used to correct the observed Zn isotope ratios.Three different methods for correcting the measured Zn isotope ratios for mass-bias drift were evaluated and compared (i) simple division of the Zn isotope ratios by the Ga isotope ratios; (ii) correction based on the power law equations given by Longerich et al.;4 and (iii) correction by a regression method. For the latter method the results for the natural abundance Zn standards were examined and the relationships between the drift of the 71Ga 69Ga ratio and the three Zn isotope ratios were established through linear regression. This approach to correcting for mass-bias drift is analogous to the analyte-inter- nal reference correlated method (AIRCM) described by Lorber and Goldbart7 for ICP atomic emission measurements with internal standards.All three correction schemes evaluatd in this study are described in more detail under Theory. The performance of the three mass-bias drift correction methods was evaluated for several case studies with different drift behaviour. This evaluation focused on the results for the 70 r 1 60 8 50 40 Dm 30 C 3 a .2 20 2 10 - n u ~ ~~ 64 65 66 67 68 69 70 71 Atomic mass Fig. 1 Relative abundances of zinc and gallium isotopes natural abundance standards because they are the only samples for which the true Zn isotope ratios are known. It was found that the regression correction method consistently gave the best results in terms of reducing the variability of isotope ratios measured for the natural abundance standards. By using customized corrections for each batch of analyses it was possible to avoid undercorrection or overcorrection of mass- bias drift which can occur with fixed correction equations.The shortcomings of the drift correction by simple division and the superior performance of the correction based on regression could be explained by considering the mathematical and statistical principles underlying those two methods. EXPERIMENTAL All isotope ratio measurements were carried out with a Perkin- Elmer SCIEX Elan 500 ICP mass spectrometer equipped with a Cetac U-5OOOAT ultrasonic nebulizer (Cetac Technologies) and a Gibson 212B autosampler (Gilson Medical Electronics). Table 1 gives the instrumental conditions used in this study. The samples analysed were purified extracts of human urine. Zinc was extracted and purified using a modification of the method published by Friel et aL8 All acids used in the preparation of samples for ICP-MS were ultrapure double sub-boiling distilled in quartz.The acids and NH40H were obtained from Seastar Chemicals and all other chemicals were from Sigma. Approximately 40 ml of thawed acidified urine was centrifuged at 5000 m s-' to remove any solids. The pH of the urine was adjusted to 5.3 f 0.2 with NaOH and 0.07 ml of 8.0moll-' ammonium acetate was added. The urine was applied to 2.0 ml Bio-Rad Chelex 100 columns (Bio-Rad Laboratories) which had been converted to the NH4+ form by adding 10 ml of 2.0 ml I-' NH40H and rinsing with 15 ml of water to remove the excess NH40H. The urinary macro- minerals (Cay Mg Na and K) were eluted off the Chelex 100 columns with 5 ml of 2.0 moll-' ammonium acetate and the trace elements were eluted with 10ml of 2,5moll-' HN03 and collected.The trace element fraction containing the Zn was evaporated to dryness made up in 2.5mol1-' HCl and applied to Bio-Rad AGl-X8 columns (0.8 ml) equilibrated in 2.5moll-' HCl. Zinc was eluted off the columns with 0.005moll-' HCl after washing the resin with ten column volumes each of 2.5mol1-' HCl and 0.5mol1-' HCl. The pure Zn fractions were evaporated to dryness in Teflon beakers on a hot-plate and diluted with 1% v/v HN03 to Zn concen- trations of typically 250 or 500 pg 1-' based on measurements by flame atomic absorption spectrometry (Smith-Hieftje 22 spectrometer Thermo Jarrell Ash). Prior to analysis by ICP-MS samples were spiked with the Ga IRIS to a final concentration of 0.02-0.046 mg 1-'. The Zn and Ga concentrations were selected such that 66Zn Table 1 Instrumentation and data acquisition parameters ICP-MS (Perkin-Elmer SCIEX Elan 500) Forward power/kW Plasma gas flow rate/l min-' Intermediate gas flow rate/l min-' Nebulizer gas flow rate/l min-l Sample flow rate/ml min-l Heater temperature/"C Condenser temperature/"(= Data acquisition Dwell time Ultrasonic nebulizer (Cetac U-5OOOAT) Sweeps per reading Readings per replicate Number of replicates Points per spectral peak 1.25 14 1.4 1.4 1 .o 140 5 35 ms for 70Zn 7 ms for 200 1 10 1 all other nuclides 16 Journal of Analytical Atomic Spectrometry January 1995 Vol.10and 69Ga yielded intensities in the 2 x 105-5 x lo5 counts s-’ range.This avoided potential signal losses due to gain suppres- sion at high count rates and ensured comparable precision (counting statistics) for all samples and standards. All ICP-MS measurements were made over a three month period rep- resenting a variety of conditions in terms of prior instrument use and detector response. A natural abundance Zn standard was analysed before and after each group of five samples. Individual sample analyses required 4 min (including sample wash-out time) and the total analysis time for sample batches ranged from 1.1 to 4.5 h. Adding the two Ga isotopes to the data acquisition programme increased the cycle time of the mass spectrometer by only 25% and had no discernible effect on the precision of individual Zn isotope ratio determinations. It should be noted that the dwell time for 70Zn was five times longer than for the other nuclides to obtain 70Zn 66Zn ratios with a repeatability comparable to that of the other isotope ratios (Table 1).The acquired isotope ratio data were saved in ASCII format report files and the regression and mass-bias correction calcu- lations were carried out off-line using the commercially avail- able spreadsheet programs Quattro Pro (Borland) or Excel (Microsoft). Quattro Pro was also used for the modelling calculations described under Theory. THEORY Internal reference (standardization) methods relate temporal variations of an analyte signal to those of a reference signal. The reference signal should be constant when noise drift or matrix interferences are absent. Any observed variations in the reference signal are considered to be due to some perturbation of the measurement system and are used to correct the analyte signal based on the assumed relationship between the two signals.The success of the correction depends largely on the assumptions about the nature of that relationship. It should be noted that when internal standardization is applied to isotope ratio measurements the two ‘signals’ are isotope ratios rather than intensities. Correction by Simple Division The simplest assumption about the relationship between the analyte and reference signals is that variations in the analyte signal are directly proportional to variations in the reference signal. In this case the correction is performed by dividing the analyte signals for all samples and standards by the correspond- ing reference signals.This approach which has been termed the line ratio internal reference method (LRIRM) by Lorber and Goldbart? is widely used in determinations of elemental concentrations by ICP atomic emission spectrometry and ICP-MS. The Myers-Tracy correction methodg is a well- known example of the LRIRM. In this paper the LRIRM is also referred to as ‘correction by simple division’. Before applying any corrections to the data collected for this study the results for the natural abundance Zn standards in each batch of analyses were normalized by setting the isotope ratios measured for the first standard equal to 1.000. Although this normalization was not necessary for the correc- tion calculations it made it easier to compare the relative drift of the Ga and Zn isotope ratios with time (cf. Figs.5-7). The LRIRM was implemented by applying eqn. ( 1 ) to the normalized isotope ratios for the natural abundance Zn standards MZn (..zn). where the left superscript N indicates normalized ratios M stands for the isotope masses 67,68 or 70 and the subscripts c and m denote corrected and measured ratios respectively. As mentioned in the introduction the performance of the LRIRM was tested by applying it only to the results for the natural abundance standards because they are the only samples for which the true Zn isotope ratios are known. For a perfect internal reference method the drift-corrected normalized Zn isotope ratios for those standards should all be 1.000.The effectiveness of any internal reference method can be discussed in terms of a precision improvement factor p which is the ratio between the RSDs of the uncorrected and corrected signals for the analyte (indicated by the subscript A) RSDA (uncorrected) = RSDA (corrected) It should be noted that the RSDs in eqn. (2) include both short-term variations from one sample to another (noise) and long-term variations within an analytical batch (drift). They do not refer to the repeatability of individual measurements (analysis repeats) that are averaged to produce the results for a single sample. In the context of this paper precision improve- ment means that the variability of results for identical standards within a batch is reduced.An internal reference method which accomplishes that actually improves the accuracy of the results for individual samples. For the LRIRM the achievable improvement in precision can be predicted from the coefficient of correlation r between the analyte and internal reference signals and a noise pro- portionality factor n which is the ratio between the RSD of the analyte signal and that of the reference signal RSDR. RSDA RSDR n = - (3) Using this definition for n which differs somewhat from that given by Myers and Tracy,g the precision improvement factor for the LRIRM is predicted by eqn. (4). n J2TC-G PLRIRM = (4) Myers and Tracy defined the noise proportionality factor (for which they used the symbol b) the same way as given in eqn. (3) only for cases with completely proportional deviations in the two signals.For cases without complete correlation they defined it as the ‘slope of the linear regression representing the least squares best fit of the experimental set of point^'.^ With this latter definition the noise proportionality factor becomes zero when the two signals are totally uncorrelated. Close inspection of eqn. (4) reveals that in order to achieve any improvement in the precision of the analyte signal ( p > l) two conditions must be met (i) r must be positive and close to 1.00; and ( i i ) n must also be close to 1.00. There are many practical situations when those conditions are not met and when the LRIRM actually results in an overcorrection or increase in noise (p < 1). The precision improvement factors found for three analytical batches examined in this study are listed in Table 2 in the Discussion section.For purposes of illustration it is convenient to plot the logarithm of the precision improvement factor p so that combinations of n and r resulting in improved precision yield positive values whereas a degradation of precision is indicated by negative values. A log(p) of 1.0 means that precision is improved by a factor of ten whereas a log(p) of - 1.0 indicates that precision is degraded by a factor of ten. Fig. 2 dramatically illustrates the very limited range of r and n values for which the LRIRM improves precision. For all combinations of r and n represented by the shaded area in that figure the LRIRM results in negative log( p ) values. Journal of Analytical Atomic Spectrometry January 1995 Vol.10 171.5 5 Fig.2 Three-dimensional surface plot of the logarithm of the pre- cision improvement factor p as a function of the correlation coefficient r and the noise proportionality factor n for correction by simple division (LRIRM) Correction Using Power Law The application of an internal reference method to isotope ratio measurements by ICP-MS was first reported by Longerich et aL4 who assumed that the relationships between the analyte signals (three different Pb isotope ratios) and the reference signal (the 205Tl '03Tl ratio) could be described by equations based on a power law. Those equations were designed to account for the mass differences between the isotopes forming a given ratio. Power law correction equations are widely used in TIMS to correct for mass fractionation effects in the ion source." Russell et a1.l' and Wasserburg et a1." compared a variety of fractionation 'laws' including those based on linear power exponential and Rayleigh distillation law equations.Both groups of authors concluded that the fractionation process in thermal ionization sources is still not well understood and that there is no universally best correction method. At this time there does not appear to be a theoretical basis for the assumption that the power law accurately describes the mass bias observed in quadrupole ICP-MS instruments. However Longerich et ~ 1 . ~ and Ketterer et al.' found empiri- cally that the power law correction works well for Pb isotope ratio measurements with T1 as the internal standard.In the present study the power law correction was applied to the normalized Zn isotope ratios for the natural abundance Zn standards using eqns. (5)-(7). N f 67Zn\ 67Zn \66Zn) (%)c= 71Ga [ ( 6*Ga),lii2 70Zn ( %)c 70Zn (s) The superscripts and subscripts are the same as for eqn. (1). No attempt was made to model the potential improvement in precision that can be achieved with the power law correction method because its performance is largely dependent on how well the power law predicts the actual behaviour of each of the analyte isotope ratios. It should be noted however that for the 68Zn 66Zn ratio the results of the power law correction and the LRIRM are identical because 68Zn and 66Zn have the same mass difference as 71Ga and 69Ga.Correction Using Regression In this internal reference method the mathematical relation- ships used for the correction are derived from regression analysis of experimental data for the analyte and reference signals rather than being based on a priori assumptions. Lorber and Goldbart7 called this approach the analyte-internal reference correlated method (AIRCM). The terms 'regression correction method' and AIRCM are used interchangeably in this paper. In a very generalized implementation of the AIRCM the functional relationships between the analyte and the reference signals may be found by least squares fitting a power series of the form y = bo + blx + b2x2 + ... + b,x" to a set of experimen- tal data where y and x represent the analyte and reference signals respectively.However for small signal fluctuations the quadratic and higher terms can be neglectedY7 resulting in linear correction equations. Since this could be verified in the present study using multivariate regression analysis the relationships between the changes of the 71Ga 69Ga ratio and those of the three Zn isotope ratios were determined by linear regression yielding equations of the form where superscripts and subscripts are the same as for eqn. (1) and bo and bl are the intercepts and slopes of the regression lines. This procedure was performed separately for each analyt- ical batch using the normalized results for the natural abun- dance Zn standards. The normalized Zn isotope ratios for all standards within a batch were then corrected for mass-bias drift using eqn.(9) N/MZn\ where b is the slope of the regression curve relating the relative drift of the Zn and Ga isotope ratios for the natural abundance zinc standards and the superscripts and subscripts are the same as for eqn. (1). The intercepts of the regression lines boy were not used in the correction calculations based on eqn. (9). This made it easier to visually compare the relative drift of the Zn isotope ratios with and without the applied correction (cf. Figs. 5-7 below). It had no effect on the precision improvement achieved by the regression correction method. In cases in which intercepts were significantly different from zero the normalized and corrected isotope ratios for the natural abundance standards within a batch were systemati- cally shifted by a mean value of bo from their ideal values of 1.000.The regression line intercepts were taken into account in the calculations correcting the results for actual samples for the mass bias itself. Mass-bias drift correction of the sample 18 Journal of Analytical Atomic Spectrometry January 1995 Vol. 10Zn isotope ratios was accomplished by applying eqn. (10). This equation is identical to eqn. (9) except that the Zn isotope ratios are not normalized. The mass bias itself was corrected using eqn. (1 l) (11) where the subscript f indicates the final isotope ratios the subscript c denotes the drift-corrected ratios the subscript n indicates the literature values for the natural abundance ratios and the term with the left superscript S is the mean of the experimentally determined isotope ratios for the natural abun- dance standards (after drift correction).It should be noted that the latter term is (1 + b,) times as large as the isotope ratio measured for the first standard in a batch. The improvement in precision that can be achieved with the AIRCM depends only on the coefficient of correlation between the reference and analyte signals and not on the noise pro- portionality factor n. The variance of the analyte signal before correction is aAZ and the regression accounts for r2 of this variance. Therefore the variance remaining after the correction is (1 - r)crA2 and the RSD of the corrected signal is RSDA (corrected) = RSDA (uncorrected) x 41 - r2 (12) Inserting eqn. (12) into eqn. (2) yields the predicted precision improvement factor for the regression correction 1 PAIRCM = - JS Eqn.(13) is symmetrical with respect to r i.e. the regression correction works equally well for positive and negative corre- lations between the analyte and reference signals. This is illustrated in Fig. 3. More importantly eqn. (13) and Fig. 3 show that the regression correction cannot degrade the pre- 1 .o Fig.3 Three-dimensional surface plot of the logarithm of the pre- cision improvement factor p as a function of the correlation coefficient r and the noise proportionality factor n for the regression correction method (AIRCM) cision of the analyte signal because even when r=0 the precision improvement factor is still 1.00. This somewhat surprising result can be understood by inspecting eqn.(9) above. Regression analysis of two completely uncorrelated signals yields a regression line with a slope b l of zero. In this case the corrected and uncorrected signals are identical and PAIRCM equals 1.00. A comparison of Figs. 2 and 3 clearly demonstrates the much broader useful application range of the AIRCM relative to the LRIRM. The PAIRCM values calcu- lated for three batches of samples are given in Table 2 in the Discussion section. Model Calculations In addition to applying different correction methods to the experimental data we also carried out model calculations to test the validity of the equations presented in this section over a broader range of conditions in terms of noise and drift than was possible with the experimental data available at this time.Eqns. (4) and ( 13) which predict the precision improvements expected for the LRIRM and AIRCM were tested by creating a variety of artificial data sets with variable amounts of Gaussian noise and systematic drift. Each data set contained 1000 numbers. After selecting one data set to represent the analyte and a different one to represent the reference the correlation coefficient noise proportionality factor and slope of the regression line were calculated. Then the 'analyte' data set was subjected to the two correction methods. A comparison of the actually observed and theoretically predicted precision improvement factors p is shown in Fig. 4. There was excellent agreement between the actual performance of both methods and theory (r > 0.9999) supporting the general validity of the derived equations.RESULTS A total of eleven case studies were evaluated for this work each one representing the results for a single batch of samples. Three of those case studies were selected for more detailed discussion in this paper because they represent the range of analytical results. For the other eight case studies the drift 2.0 1.5 1 .o - W 6 0.5 d - Q 0 - -0.5 -1.0 *AA A A I 0 0.5 1 .o 1.5 2.0 -1.0 -0.5 log( p predicted) Fig. 4 Comparison of observed and predicted logarithms of precision improvement factors p based on model calculations using the A LRIRM and 0 AIRCM Journal of Analytical Atomic Spectrometry January 1995 Vol. 10 19behaviour was intermediate between that found in the three selected cases. In eight of the eleven cases there was a significant and systematic drift of the mass bias for the Zn and Ga isotope ratios.The largest drift observed on a single day was close to 4% compared with the results for the first natural abundance standard in a batch. There was no apparent relationship between the extent of drift of the isotope ratios and the drift of the raw intensities for the individual isotopes. In two cases the raw intensity for the 66Zn reference isotope changed by more than 30% over a 3-4 h period while the isotope ratios varied less than & 1.5%. It is noteworthy that the mass bias most often increased with time during an analytical session. This may have been due to temperature effects or to gradual pressure changes in the quadrupole vacuum chamber.The degree to which the individual Zn isotope ratios followed the 71Ga 69Ga ratio was quite variable both in terms of the magnitude of the correlation coefficients and the slopes of the regression lines. Correlation coefficients for the three Zn isotope ratios and 11 case studies varied between 0.3282 and 0.9913. They were typically lowest for cases with very little drift. The slopes of the regression lines ranged from - 1.74 to 1.93; about 18% of all calculated values were negative. For each of the three selected case studies four figures are presented in this section; all of them are based on results for the natural abundance Zn standards [Figs. 5-7 (a)-(d)]. The first figure [(a)] shows the temporal changes of the Ga and Zn isotope ratios relative to the values measured for the first standard analysed in a given batch.The other three figures [(b)-(d)] show the results obtained with the simple division correction (LRIRM) the power law correction and the regression correction (AIRCM) respectively. 1.02 Case 1 In this analytical batch all isotope ratios systematically increased with time [Fig. 5(a)]. The Ga IRIS followed the 68Zn 66Zn ratio most closely while the 67Zn 66Zn ratio changed at a slower rate (about 0.5 x ) and the 70Zn 66Zn ratio drifted more rapidly [about 2 x see Fig. 5 ( a ) ] . Consequently the simple division method undercorrected the 70Zn 66Zn ratio and overcorrected the 67Zn:66Zn ratio [Fig. 5(b)]. The power law and regression corrections were almost equally successful in removing drift for the natural abundance Zn standards [Fig. 5(c) and ( d ) ] .Of the 11 data sets examined for this study this was the only one for which the power law correction performed that well. It should be noted that with a limited range of mass-bias drift of a few percent the power law correction method gives very similar results to the regression method with fixed slopes of the regression lines of 0.5 1 and 2 respectively. This is due to the fact that the functions y=x1I2 y = x and y = x 2 have first derivatives with the approximate values of 0.5 1.0 and 2.0 when x is close to 1.00. (a) - Case 2 The results from this analytical batch demonstrate a failure of the power law correction. The Ga IRIS closely followed the 67Zn 66Zn and 70Zn 66Zn ratios. In comparison the 68Zn 66Zn ratio drifted more slowly [Fig.6 ( a ) ] . Since this behaviour is very different from that assumed for the power law correction [eqns. (5)-( 7 ) ] the 67Zn 66Zn ratios were undercorrected and the 68Zn 66Zn and 70Zn 66Zn ratios were overcorrected by this method [Fig. 6 ( c ) ] . Even the simple division correction method produced better results for the 67Zn 66Zn and 70Zn:66Zn ratios [Fig. 6 ( b ) ] . However by far the best results 1 l . O 1 ~ .oo !E 0.98 0.99 i I I I J 0 1 2 3 4 0.98 ' t 0 1 2 3 4 'Tirnelh Fig. 5 Results of case study 1. (a) Relative mass bias drift for the 67Zr1 66Zn (V) 68Zn 66Zn (+ ) "Zn 66Zn (A) and 71Ga 69Ga (m) ratios with time. Results for the Zn isotope ratios after correction using (b) simple division (c) the power law equations and ( d ) the regression correction method 20 Journal of Analytical Atomic Spectrometry January 1995 Vol.10al - a t ( C) 1.01 1 .oo 0.99 0.98 I 0 1 2 3 4 0 1 2 3 4 Time/h Fig. 6 Results of case study 2. (a) Relative mass bias drift for the 67Zn 66Zn (V) 68Zn 66Zn (+) "Zn 66Zn (A) and 71Ga 69Ga (m) ratios with time. Results for the Zn isotope ratios after (b) correction using simple division (c) the power law equations and (d) the regression correction method 1.00 I 0.99 - 0.98 ' I I I I I 0 1 2 3 4 5 0.99 I 1 . 1 I I 0 1 2 3 4 5 Time/h Fig. 7 Results of case study 3. (a) Relative mass bias drift for the 67Zn 66Zn (V) 68Zn &Zn (+) 70Zn 66Zn (A) and 7'Ga 69Ga (m) ratios with time. Results for the Zn isotope ratios after (b) correction using simple division (c) the power law equations and (d) the regression correction method Journal of Analytical Atomic Spectrometry January 1995 VoZ.10 21were achieved with the regression correction method which removed all systematic drift from the Zn isotope ratio data [Fig. 6(d)]. Case 3 This batch of samples required a total analysis time of 4.5 h and included nine natural abundance Zn standards. The original data for the standards showed only random variations within the error limits of the measurements; there was no systematic drift of the isotope ratios with time [Fig. 7(a)]. Owing to the absence of a strong correlation between the Ga IRIS and Zn isotope ratios (r < 0.523) the simple division and power law correction methods actually increased the overall spread of the data [Fig.7(b) and (c)]. The regression correction on the other hand had no adverse effect on the variation range of the Zn isotope ratio results [Fig. 7 ( d ) ] as was expected from theory. DISCUSSION Table2 is a compilation of the coefficients of correlation between the normalized Ga and Zn isotope ratios as well as the regression line slopes noise proportionality factors and precision improvement factors with their logarithms for the three case studies and three correction methods. The precision improvement factors listed were calculated from the experimen- tal data before and after correction and not from the predictive eqns. (4) and ( 1 3 ) given under Theory. For case studies 1 and 2 (Figs. 5 and 6) all correlation coefficients were in the range 0.813-0.991.The slopes of the regression lines for the 67Zn:66Zn ratio were 0.433 and 0.968 while those for the 68Zn:66Zn ratio were 0.901 and 0.535 and those for the 70Zn 66Zn ratio were 1.94 and 1.1 1 respectively. Figs. 5(b) and 6(b) confirm the theoretical prediction that the simple division correction method (LRIRM) only performs well when the correlation coefficient r is close to +1.00 and the slope of the regression line is also close to + 1.00. As Table 2 shows the regression line slope is approximately equal to the noise proportionality factor n for high values of r. The power law correction method is similarly restrictive in that it only performs well when r is close to $1.00 and the slopes of the regression lines are close to 0.500 for the 67Zn:66Zn ratio close to 1.00 for the 68Zn:66Zn ratio and close to 2.00 for the 70Zn:66Zn ratio.As pointed out earlier this type of relationship was rarely observed. For all 11 case studies the regression line slopes for the 67Zn 66Zn 68Zn 66Zn and 70Zn 66Zn ratios averaged 0.312 & 0.840 0.541 0.432 and 1.021 & 0.727 respectively. The IRIS/regression method always showed the best per- formance among the three correction methods tested. The RSD of the drift-corrected data for an entire batch was typically of a magnitude similar to the standard error of the mean of the individual isotope ratio determinations of 0.17%. This is illustrated by Figs. 5(d) 6 ( d ) and 7(d). The residual RSDs for all Zn isotope ratios in the three selected cases ranged from 0.09 to 0.32% with a mean value of 0.18%.The highest reduction in drift was obtained in case study 2 in which the precision of the 70Zn:66Zn ratio was improved by a factor of 7.6 (Table 2). Considering all 11 case studies the regression correction method reduced the variability of the three Zn isotope ratios for the natural abundance standards by an average factor of 2.5. The method performed equally well for all three Zn isotope ratios. By establishing the relationships between the analyte and reference isotope ratios for each analytical batch the regression correction method is very flexible. A particularly attractive feature of this method is that it can be applied to all situations without fear of degrading precision. Case study 3 illustrates that the regression correction does not increase the spread of the data even when the variations of analyte and reference isotope ratios are only weakly correlated.When there is no correlation at all the results remain unchanged. Negative correlations between analyte and reference isotope ratios are equally effective in reducing mass bias drift as positive ones. The degrees to which the IRIS/regression method can improve precision for a given analytical batch can be predicted directly from the coefficient of correlation between the analyte and reference isotope ratios using eqn. (13). This allows the analyst to decide quickly whether carrying out the correction calculations is worthwhile. It also means that any improve- ments in precision are statistically significant even if they are small because the improvements are inherent in the deposition (ie.correlation) of the experimental data. Although the correc- tion must be carried out off-line after a batch of analyses is completed the computations are relatively simple and can be performed easily with modern spreadsheet software. The regression method presented in this paper can also be applied to other types of ICP-MS measurements using internal standardization such as the conventional determination of elemental concentrations. In the area of isotope ratio measure- ments by ICP-MS the correction of mass-bias drift is particu- larly important in situations in which small errors in the experimentally measured isotope ratios are amplified by the calculations used to determine a derived quantity.This is the case in the computation of relative enrichments of isotope tracers3 and in the determination of elemental concentrations by isotope dilution mass spectrometry.12 Financial support for this work from the California Department of Health Services Hazardous Materials Laboratory (contract 91- 12843) is gratefully acknowledged. Table 2 Coefficients of correlation (r) between the normalized "Ga 69Ga ratio and the normalized Zn isotope ratios regression line slopes (bl) noise proportionality factors (n) and the precision improvement factors and their logarithms for the three case studies and three correction methods r bl n PLRIRM PAIRCM P ~ o w e r law LOg(PLRIRM) - Log(PPower law) LOg(PAIRCM) 0.8128 0.4333 0.5349 0.828 1.683 1.718 0.082 0.226 0.235 0.9437 0.9012 0.9544 2.844 2.844 3.027 0.460 0.460 0.48 1 0.9629 1.9361 1.9917 1.871 3.639 3.673 0.272 0.561 0.565 0.9885 0.9678 0.9787 6.486 1.991 6.622 0.812 0.229 0.821 0.9863 0.5348 0.5459 1.153 1.153 6.081 0.062 0.062 0.784 0.99 13 1.1117 1.1189 6.067 1.233 7.586 0.783 0.09 1 0.880 0.3282 0.1725 0.5237 0.542 0.883 1.059 - 0.266 - 0.054 0.025 0.5231 0.1827 0.3490 0.401 0.401 1.175 - 0.397 - 0.397 0.070 0.4600 0.3743 0.8117 0.849 0.561 1.125 .0.07 1 .0.251 0.051 22 Journal of Analytical Atomic Spectrometry January 1995 Vol. 10REFERENCES Morgan P. N. Woodhouse L. R. Serfass R. E. Roehl R. and King J. C. FASEB J. 1993 7 A279. Morgan P. N. Woodhouse L. R. Abrams S. A. Serfass R. E. Roehl R. and King J. C. FASEB J. 1994 8 A918. Woodhouse L. R. Morgan P. N. King J. C. Roehl R. and Gomez J. ICP lnf. Newsl. 1994 20 25. Longerich H. P. Fryer B. J. and Strong D. F. Spectrochim. Acta Part B 1987 42 39. Ketterer M. E. Peters M. J. and Tisdale P. J. J. Anal. At. Spectrom. 1991 6 439. Amarasiriwardena C. J. Krusheva A. Foner H. Argentine M. D. and Barnes R. M. J. Anal. At. Spectrom. 1992 7 915. Lorber A. and Goldbart Z. Anal. Chem. 1984 56 37. 8 Friel J. K. Naake V. L. Miller L. V. Fennessey P. V. and Hambidge K. M. Am. J. Clin. Nutr. 1992 55 473. 9 Myers S. A. and Tracy D. H. Spectrochim. Acta Part B 1983 38 1227. 10 Wasserburg G. J. Jacobsen S. B. DePaolo D. J. McCulloch M. T. and Wen T. Geochim. Cosmochim. Acta 1981 45 2311. 11 Russell W. A. Papanastassiou D. A. and Tombrello T. A. Geochim. Cosmochim. Acta 1978 42 1075. 12 Chiba K. Inamoto I. and Saeki M. J. Anal. At. Spectrom. 1992 7 115. Paper 4/01519C Received March 14 1994 Accepted September 12 1994 Journal of Analytical Atomic Spectrometry January 1995 Vol. 10 23

ISSN:0267-9477    

DOI:10.1039/JA9951000015

出版商:RSC    

年代:1995

数据来源: RSC