Greetings from down-under and a Happy New Year to all our readers. This is our second CITAC News and it contains articles relating to previous and current CITAC activity. I hope these are of interest to you.
1996 was a busy year commencing with our annual pilgrimage in March to Pittcon, in (very cold) Chicago. A full report on the activities carried out there appeared in the 14th issue of the VAM Bulletin. At the main CITAC Working Group meeting, a review of all current tasks was undertaken. It was at this meeting that Bernard King, who had been Chairman of CITAC since its inception in 1993, handed over to me. Big shoes to fill indeed! We are all grateful to Bernard for his tireless efforts and I thank him for his continuing support and guidance. The membership of the group was reviewed in Chicago and I am pleased to see that we are now further "internationalised" with most regions in the world now being represented (refer back page). The debate must span all continents.
In September, CITAC and Eurachem conducted a 2 day workshop at Noordwijkerhout in the Netherlands. This was attended by 60 delegates. A workshop on traceability and comparability in analytical chemistry usually "stiffens the sinews and summons up the blood" and this gathering was no exception! It was pleasing to note that there was consensus on some of the broader issues but there is still much to do and this includes addressing the misunderstandings caused by language. We cannot allow ourselves to get "bogged down" by semantic debate about definitions when having group discussions on fundamental concepts but we do need to understand and agree on terms like traceability, standard, validation, verification etc etc. I applaud the efforts in the excellent bimonthly Springer Journal "Accreditation & Quality Assurance" to tackle this problem. A full report on the Netherlands workshop will appear in this journal shortly.
I was particularly pleased to see CITAC work so closely and successfully with Eurachem - CITAC I believe has a very important role in harmonising (but not duplicating) activity already undertaken by other bodies and we should further develop our relations with other relevant national & international groups - time is too short for us to sit with different hats behind closed doors; and there are not enough "practitioners" to go around, particularly at a time when honorary contributions (in time and money) from key people are already at a premium.
Throughout the year, a lot of work has also been carried out by correspondence and ad-hoc meetings. I thank my colleagues for their efforts which will again be reviewed at the next working group meeting on Monday 17 March in association with Pittcon 97 in Atlanta. The working group will also address the pressing subject of the need (or otherwise) to restructure (formalise) CITAC. A draft MOU has been prepared and will be reviewed. Attention will also be given to future CITAC funding strategies - we are currently solely dependent on the voluntary contributions from our sponsors - refer page (3). In addition to the main working group meeting, CITAC will also conduct a symposium on world-wide interlaboratory comparisons on Sunday 16 March and will also be involved in another symposium on traceability and QA, in the context of world trade, on Thursday 20 March.
Later this year, we also hope to conduct some CITAC activity in association with BERM (Antwerp, April 21-25) and the International Congress on Analytical Chemistry (Moscow, June 15-21). Plans for CITAC activity in 1998 are already underway and this includes meetings and workshops in Sydney (in association with the ILAC conference) between 18-23 October.
Dr Terry Quinn, Director of BIPM has stated previously that "it is actually impossible to state whether the quantity of lead in drinking water ten years ago is less or more than the quantity found today". Unfortunately the results of recent studies like IMEP 6 support this - see page (7) - in this case results for copper & cadmium are displayed. The results of other studies, some of which will be reviewed at the CITAC symposium in Atlanta, also show cause for concern but we must not be discouraged. The challenge is there and we must, like all good chemists, find solutions. The further development of metrology in chemistry will assist this process but it must translate down (or is it up?) the traceability chain to working level measurements.
I feel confident that CITAC, in association with other groups, can make further progress in providing mechanisms to improve the traceability and comparability of analytical results and I look forward to a continuation of the mentally stimulating debate and the emergence of practical solutions.
I wish you all the very best for 1997 & look forward to meeting "old" friends (and hopefully making new ones!) at our forthcoming events. If you do require further information about CITAC please do not hesitate to contact the secretariat at:
The CITAC Secretariat
Tel + 44 181 943 7614 Fax + 44 181 943 2767 Email citac@lgc.co.uk
Regards,
Alan Squirrell
The "CITAC '94 Hong Kong Symposium" was held at the Grand Hyatt Hotel in Hong Kong on 14 and 15 October 1994 immediately before the 1994 International Laboratory Accreditation Conference (ILAC) meeting. This two-day Symposium, jointly organised by the Hong Kong Chemical Society and the CITAC Working Group with support from the Government Laboratory, was well attended by over 80 local and overseas participants from 16 countries.
The two-day discussion, which was built on previous meetings held in Atlanta and Chicago, USA, provided an opportunity for laboratory leaders and scientists from around the world to further consider the needs and input from the Far East and Pacific rim countries to develop the CITAC initiatives. In the first day's program, the Government Chemist of Hong Kong was invited to give an opening address followed by Dr. B King, Chairman of CITAC Working Group, and Dr T L Ting, Chairman of the Local Organising Committee. The scientific program then began with Dr King's presentation entitled "International Collaboration - Why We Need to Agree to Agree" which facilitated intense debate on international collaborative activities. The Workshop which followed was well attended and generated a lot of useful discussions on quality of analytical measurements. The theme of a record Workshop held in the afternoon was about measurement traceability and uncertainty, and resulted in an overwhelming agreement amongst participants that a harmonised international guidance should be produced for laboratories on how to maintain the traceability of measurements as well as to arrive at an agreement on the calculation of uncertainty.
"Validation of Analytical Methods", the first presentation of the second day of the Symposium, emphasised the key principles under which laboratories should observe to improve the quality of analytical measurements. Use of validated methods, reference materials, implementation of quality assurance protocols, participation in proficiency testing programs and laboratory accreditation schemes were the issues discussed under "Foundation of quality" in the second session. The final session of the second day discussion focused on regional efforts in collaboration work, presented by Dr T L Ting of the Government Laboratory, Hong Kong, followed by Professor Yasuda of Japan, and Professor Huang of China.
The Symposium in Hong Kong has succeeded in providing a valuable forum for the exchange of views on quality issues of analytical measurements. It also created an excellent opportunity for the local testing laboratories in establishing links with overseas laboratories and standards agencies.
Tai Lun Ting-Government
Laboratory Hong Kong
_________________________
I would like to again thank our marvellous hosts in Hong Kong - I look forward to future
events in the Asia-Pacific Region.
-- Alan Squirrell
As a follow-up to the 3rd CITAC Workshop on Education and Training of Analytical Chemists held in New Orleans, USA in March 1995, the Government Laboratory of Hong Kong organised a one-day seminar on education and training of chemists in February 1996 at the Metropole Hotel, Kowloon. Prof. Julian Tyson of the University of Massachusetts, USA, one of the key-note speakers of the 3rd CITAC Workshop, was invited to conduct the seminar and a workshop entitled "Curriculum Reform - Identifying Why and How". The issues of education and training of analytical chemists in the USA and UK, and a review of curricula of university chemistry courses in Hong Kong were discussed at the seminar and the workshop with a view to harmonising the curriculum structure of local chemistry education. The seminar, being the first of its kind in Hong Kong, was well attended by some 50 professionals and academics from the public service and the six local universities that adopted either UK or USA education system.
Tai Lun Ting-Government Laboratory Hong Kong
The need for a best practice QA guide for R & D and non-routine analysis originated in EURACHEM but the initiative was then taken by CITAC in 1995. One of the first steps was the formation of a common EURACHEM/CITAC Working Group in London, October 1995. The common activities of EURACHEM and CITAC should help to avoid duplicate work and ease international harmonization and acceptance.
The WG comprises about 10 full members and roughly 30 only corresponding members. Additionally up to now at least 30 other interested people have contributed to the work by sending comments from all around the world. Prof. Cammann, University of Munster, Germany, was elected as chairman of the WG representing EURACHEM as Dr Steck, BASF AG, Germany, does on behalf of CITAC. To date, two meetings of the WG have been held - May 1996 (Prague) and December 1996 (Ludwigshafen).
The new guide is aimed at analytical staff, clients, qualify and technical managers in testing laboratories as well as assessors or peers. The emphasis of advice is on QA best practice and on the application of good analytical science. Though not specifically oriented towards accreditation the guide will probably also have a section on external verification dealing with the accreditation of R & D and NR laboratories. However as the guide will not be oriented around accreditation advice will mainly not be prescriptive. The current concept of the guide is founded on a nested structure encompassing three fields (Analytical Task, Technical Quality Elements and Organisational Quality Elements). The guide tries to avoid following any one particular existing quality management standard as this could necessary limit the applicability of the guidance.
The contents discussed in Prague are listed in the following:
The guide will offer a flow chart which can be used as useful "decision tree" for the various stages of the analytical task.
It is hoped that the WG can offer a draft version to the analytical community for comment early next year, at least at Pittcon '97 in March.
Werner Steck - BASF Germany
Professor Dr Wolfhard Wegscheider was elected CITAC Vice-Chair in December, 1996, by a secret ballot of CITAC Working Group members.
Wolfhard Wegscheider is Professor of General and Analytical Chemistry at the University Leoben and co-owner of a small commercial laboratory in Austria. He earned an engineering degree in chemistry and a doctoral degree in analytical chemistry from the Graz University of Technology, before winning a Fulbright Scholarship for postdoc work in Denver, Colorado, in the USA.
His research interests are fundamentals of analytical instrumentation, trace analysis by spectroscopic methods and chemometrics. Currently he serves as Austrian delegate to EURACHEM.
In his election address to CITAC working Group members, Prof. Dr Wegscheider regarded CITAC as a forum for the most widespread proliferation of quality matters in analytical chemistry. He said that it had the potential of developing into a well-respected partner of other world-wide organisations, such as ISO, IUPAC and ILAC.
"It is my vision", wrote Prof. Dr. Wegscheider, "to develop CITAC into a more balanced body representing laboratories on all continents and subcontinents. This also relates to the need to further harmonise not only issued international documents but also their interpretation through mutual discussion and co-ordination." Prof. Dr Wegscheider will remain as Vice chair until 1998, when he will take over as CITAC Chair from Alan Squirrell.
Keith Marshall - CITAC Secretariat UK
We now have a CITAC homepage http://www.vtt.fi/ket/citac. Look us up on the web and please let the secretariat know if you have any suggestions about additional material. Our thanks to Veikko Komppa for making this possible.
The International Laboratory Accreditation Cooperation (ILAC) has recently resolved to work closely with CITAC. This is most welcome as the main aim and objective of both groups is to improve the reliability of test results. The ILAC home page (www.ilac.org) cross-references the CITAC homepage (see above).
We are indebted to the organisations who continue to sponsor CITAC's activities. In 1995/6, contributions were received from:
If your organisation would like to make a small donation this year please do not hesitate to contact the CITAC Secretariat. Thank you.
The European standard for General criteria for the operation of testing laboratories (EN45001:1989) is widely applicable to a variety of types of measurement. It has long been accepted that in certain areas, for example chemical testing, some form of supplementary interpretation was appropriate to assist laboratories implement EN 45001. With that in mind a joint EURACHEM and WELAC working group produced such a document, which was published in April 1993. This document rapidly became established as an important guide and its value was also recognised outside Europe where in many areas accreditation against ISO Guide 25 derived standards was often poorly developed. Even where accreditation was not necessarily seen as the obvious way of assuring quality it was recognised that a guide stating best practice in chemical measurement would be very useful. As a result the original EURACHEM/WELAC text was revised by CITAC to produce a guide which whilst still acknowledging the value of accreditation placed less emphasis on it and concentrated more on good quality assurance practice. The CITAC Guide was accordingly published in December 1995 and has since met with critical acclaim. The guide is primarily aimed at routine work although there is some mention of additional measures to be adopted for non-routine work. However a sister guide, covering specifically non-routine work and research & development, is currently under development (refer page 2).
The adoption of ISO Guide 25 and derived standards as the prime means of assuring quality in testing and calibration laboratories continues to progress strongly. Whereas ten years ago, there were very few mature schemes outside of Europe, excepting of course Australia, Hong Kong and New Zealand, now more and more countries are setting up their own national schemes and ILAC (the International Laboratory Accreditation Conference) now has more than 40 members.
Although the CITAC Guide was not developed specifically with accreditation in mind CITAC has been gratified to note that ILAC has recently passed a resolution to ".. consider the use of CITAC Guide 1 by laboratory accreditation bodies and analytical chemical laboratories".
The future may well see revisions of these guides. Work is currently in hand within ISO/CASCO to revise ISO Guide 25 and make it more of a standard. Although still in draft form it appears significantly different to previous editions. The terminology used in the drafts together with a greatly changed layout are consistent with convergence with the ISO 9000 series of standards, themselves currently the subject of revision by ISO/TC 176. What effect these revisions have on the existing chemistry guides remain to be seen, since the actual QA practices required probably will not change a great deal. What would be more interesting and almost certainly require more wide-ranging alteration would be the scenario where ISO Guide 25 and ISO 9000 were amalgamated to form a single, all-embracing laboratory standard. Whether or not this will happen remains to be seen. There are no such stated plans from the standards bodies at present but recently a number of surveys have been carried out to look at the satisfaction of accreditation and certification users, i.e. laboratories, with the standards. An international survey organised by ILAC has considered the merits of accreditation versus certification although no report has been seen. A recent survey carried out by LGC in the UK looked at numerous aspects of quality systems. Among the conclusions it was noted that by far and away the preferred option would be harmonisation of the quality standards. There is no intention to publish this report in full however it is intended to publish a detailed summary of the report in a journal in the near future.
The EURACHEM/WELAC Guide is available from LGC, enquiries should be directed to Mr D Binney, Technology Access Group, Laboratory of the Government Chemist, Queens Road, Teddington, Middlesex TW11 0LY, UK Fax +44 181 943 2767.
The CITAC Guide 1 is available from the Royal Society of Chemistry (contact Jenny McCluskey), Thomas Graham House, Science Park, Cambridge, CB4 4WF, UK Fax +44 1223 423429.
If you have any problems obtaining either guide please contact the CITAC Secretariat at LGC.
References
Traceability is universally recognised as one of the basic prerequisites for comparability of the results of measurements made in different laboratories, in different countries, and of the conclusions drawn from these results.
In the field of physical measurements traceability is implemented by means of a hierarchical system of measurement standards terminating at international or national standards for SI units. Therefore the discussion on how to implement traceability in the field of chemical measurements (viz. in quantitative chemical analysis) has mainly been devoted to the pro's and con's of building up an analogous hierarchy of measurement standards. Due to the focus on metrology system aspects, the fundamental practical problem of how to actually link a measurement result to one or several reference standards such that it can be considered traceable was largely left untouched. Therefore CITAC is developing a guidance document which sets out basic principles, and describes detailed procedures, for establishing traceability of analytical results in practice. It will be applicable to all fields of chemical composition analysis, but also to measurements of physico-chemical parameters and other quantities of relevance to chemical analysis.
Evidently requirements (ii) and (iii) call for standardization. For the units of physical quantities the standardization problem was solved by establishing the International System of Units (SI) in 1960. The confusion about different uncertainty measures continued beyond that date. Only recently a candidate standard uncertainty measure with the potential of world-wide acceptance has appeared. This is the "standard uncertainty" proposed by the Guide to the Expression of Uncertainty in Measurement.
The remaining requirement (i) is the most demanding one. For short, known uncertainty means that in the uncertainty budget of the measurement no major contribution has been overlooked, and that the quantification and combination of uncertainty contributions has been done correctly. Traceability, where applicable, simultaneously solves all these problems by comparison between measured values and corresponding reference values.
In practice there are basically two different strategies for making use of comparisons between measured values and reference values: calibration and verification. For short, in calibration the comparison results are used to derive measurement results from raw measured data, while in verification measurement results are tested for compatibility with acknowledged reference values. In calibration different methods are used, depending on the type of task. For example, calibration can refer to a measuring system or to a measurement standard. In the case of a measuring system, the purpose of calibration can be determination and correction of bias or determination of the relationship between the values of measured responses and the measurand, i.e. the target quantity to be measured.
metrological calibration, i.e. determination of bias;
analytical calibration, i.e. determination of response characteristics;
verification, i.e. testing consistency with reference data.
For each of these categories different procedures are available. Among others, the following options apply:
single-level or a multi-level comparison;
interpolation or regression;
uncertainty propagation or statistical analysis of residual scattering.
In the CITAC guidance document the main traceability strategies will be explained, and corresponding procedures will be elaborated in detail. The descriptions will be given in general terms using the established definitions of metrology, mainly taken from the International Vocabulary of Basic and General Terms in Metrology. Evaluation and expression of uncertainties will conform with the Guide to the Expression of Uncertainty in Measurement. The presentation will be technical, by necessity, making use of statistical tools on the level of the Guide.
For determining the uncertainty of a candidate analytical method, the method is applied to appropriate reference samples. The results are compared with the reference values attributed to the reference samples. Alternatively, the candidate method and a reference method are applied in parallel to appropriate samples. The results of the candidate method are compared with those of the reference method. First, the measurement results and the corresponding reference values are compared, taking into account the relevant uncertainties. Second, if significant bias is found, a bias correction for the specified measuring range is derived. Third, the uncertainty of the results of future measurements, including bias correction, is calculated by combination of two contributions: The uncertainty of the uncorrected measurement result and the uncertainty of the correction.
For determining the relationship between instrumental response and the target quantity to be measured - typically the content of a specified analyte in a specified matrix - the response is measured on calibration samples of known analyte content, covering the measuring range. From the comparison between the measured responses and the reference values of the analyte content, the parameters of the response curve (e.g. slope and intercept of a straight line) are derived, including the uncertainties of these parameters. By means of these data, the analyte content of an unknown sample can be predicted from its measured response, and from the uncertainty of the measured response, and from the uncertainty of the measured response and the uncertainties of the response curve parameters the uncertainty of the predicted analyte content can be calculated.
For examining whether a measurement result is consistent with a corresponding reference value, the observed difference is tested for significance against the relevant uncertainty - typically a combination of the uncertainties on the measurement result and on the reference value. Using appropriate statistics, this significance test can be organised in a single- level or multi-level mode.
The International Measurement Evaluation Program (IMEP) has now completed its 6th measurement round, (IMEP-6) Trace Elements in Water. An overview of the results was recently presented at a EURACHEM/CITAC workshop and attracted considerable interest from the delegates. They will be reviewed again at the forthcoming CITAC Symposium in Atlanta (March 1997).
The IMEP is co-ordinated from the Institute for Reference Materials and Measurements (IRMM) and run under the support and auspices of IUPAC, EURACHEM, EUROMET and CITAC. The program aims at being a tool for field laboratories to compare their results to SI-traceable values and is offered also to regulating and accrediting bodies. Samples with undisclosed values are sent to interested laboratories which return their measurement result with a statement of uncertainty claiming to contain the "true value". The SI-traceable values are established by Isotope Dilution Mass Spectrometry (IDMS) which has the potential to be a primary method of measurement. For IMEP-6, this was done in collaboration with NIST (USA) and University of Regensburg (Germany). Uncertainty ranges are evaluated according to ISO-BIPM and EURACHEM guidelines. A strategy of IMEP is that the SI-traceable values (certified values), which will serve as references, should be obtained by means of well understood measurement processes. Values established by other techniques and serving as references in the IMEP are referred to as "assigned values". IMEP rounds are run in cases where the objective evaluation of measurement results are important, e.g. for toxic and life-essential elements in water and body fluids.
In IMEP-6, fourteen trace elements (Ag, B, Ba, Cd, Cu, Fe, Li, Mo, Ni, Pb, Rb, Sr, T1 and Zn) were under investigation in a synthetic and a natural water material. Some 200 laboratories in 30 countries participated to this IMEP round of which 29 participants were regionally co- ordinated from Chile. The first results from the certification work and evaluation of participants' results will soon appear and a more extensive publication is scheduled for 1997.
| Table 1, IMEP-rounds planned in near future | |||
|---|---|---|---|
| elements of interest | |||
| IMEP-7 | Trace elements in human serum | Ca, Cl, Cu, Fe, K, Li, Mg, Na, Se, Zn | 1997-98 |
| IMEP-8 | n( |
1997-99 | |
| IMEP-9 | Trace elements in water | Same as in IMEP-6 and similar to IMEP-3 |
1997-98 |
IMEP-rounds planned in near future are shown in Table 1. IMEP-7, Trace Elements in Human Serum, is planned in close co-operation with organisers of external quality assurance programs in the Nordic countries. There will, however, be room for approximately 150 international participants. Laboratories interested in this or in any other future round, or simply in more information, please contact IRMM.
Mrs Lutgart Van Nevel Tel: +32(0)14 571 702; Fax: +32(0) 584 273; 14 591 978 Dr Philip Taylor Tel: +32(0)14 571 615; Fax: +32(0)14 584 273; 591 978 Paul De Bièvre, Ulf Ömemark, Lutgart Van Nevel and Philip Taylor Institute for Reference Materials and Measurements European Commission-JRC Retieseweg, B-2440 GEEL (Belgium)