Interlaboratory study to improve the quality of trace element determinations in rainwater

This is the first publication which describes the development of a reference material (RM) for the determination of 11 trace elements (Cu, Pb, Mn, Ni, Zn, Fe, Cd, Co, V, As and Al) in rainwater at microgram per liter concentrations. An interlaboratory comparison study for the determination of trace elements in rainwater was carried out for material performance studies to establish analyte concentrations with a stated uncertainty. Fifteen reputed laboratories from Asia, Europe and North America participated in the study. These laboratories used their regular in-house methods to analyze the rainwater samples. The aim of this study is to establish concentration levels of trace elements in rainwater based on interlaboratory study results. Details of the production, homogeneity and stability of the reference sample are given in this article. The organization of the study and the quality assurance measures undertaken at the organizer's laboratory are described. The analytical results obtained from individual laboratories and the analytical methods used for the determination of trace elements in rainwater are discussed. Based on the results obtained from the intercomparison study, certified values as well as informative values are assigned to the 11 trace elements in rainwater.     

External quality assessment schemes for clinical analysis in Russia

 The history and the present condition of external quality assessment (EQA) schemes for clinical laboratories in Russia are described briefly. The creation of EQA programmes started in Russia in the 1980s. Now almost 20 years later these schemes have been transformed. The National External Quality Assessment Scheme ensures quality control in the clinical chemistry sector (more than 2000 laboratories) and is the most powerful scheme in Russia. The (Sistema Vneshnego Kontrola Katchestva, *) (BKK) system, covering about 120 Russian laboratories, and a lot of local regional programmes (mainly in Siberia), is also very active. The purposes and design of the operating programs, reference materials used, algorithms of estimation, modes of result representation and development prospects are considered. The basic obstacle to the development of EQA schemes in Russia is financial restriction.     

Quality assurance in clinical chemistry laboratories in the UK

 Since the mid-1960s quality assurance in clinical chemistry has progressed from a need to define and improve precision and accuracy in analytical test procedures to an all-embracing process of assuring that the whole process of pre-analytical, analytical and post-analytical phases of handling patient samples is managed effectively and efficiently. Automated and computer-controlled equipment has reduced many of the analytical errors, in particular in imprecision, that were present in manual analysis. New management techniques have been developed to control the quality and appropriateness of results. Developments in internal quality control and external quality assessment procedures have enabled laboratories to continually improve the quality of assays. Laboratory accreditation and external quality assessment scheme accreditation have ensured that peer review and peer pressure have been applied to both laboratory and external quality assessment scheme performance. As the NHS reviews its priorities and places more emphasis on primary care provider demands, hospital laboratories will of necessity assist with near patient testing outside the laboratory. This will provide new challenges to the quality of the service provided. Received: 2 July 1998 · Accepted: 1 August 1998     

Developing external quality assessment programmes for primary health: care level in resource limited countries

Laboratory services are an essential component of health care delivery in tropical countries and play a vital role in improving the accuracy of clinical diagnosis and the investigation of disease outbreaks. In developing countries, laboratories face numerous constraints to providing quality services, including poor selection of techniques, difficulties in equipment availability and maintenance, and shortages of supplies, staffing and supervision. Currently in the eastern African countries (Kenya, Tanzania and Uganda), internal quality control procedures are inconsistently carried out in most laboratories. National External Quality Assessment Schemes (EQAS) have been established in all countries addressing a limited number of tests, but are constrained by difficulties of sustainability and poor coverage. The Laboratory Programme of the African Medical and Research Foundation (AMREF) has been operating a simple EQAS for primary heath care laboratories since 1993. Tests addressed are those carried out in primary health care laboratories in eastern Africa. A total of 81 laboratories from 5 countries in the eastern African region have participated in the scheme since 1993 and 9 distributions were submitted since the start of the scheme. No laboratory participated in all distributions; 24 (30%) laboratories participated in 4 or more distributions. Of these, the hospital laboratories in Kenya and Tanzania showed improved average mean scores between the first two and subsequent distributions. The educational benefit of participation in the scheme is emphasised. There was an overall low rate of participation of laboratories (35%) once the scheme was expanded to include laboratories outside direct AMREF project activities. Contributing factors include shortages of staff and lack of time in busy rural laboratories, together with difficulties in communication; however, the voluntary nature and lack of appreciation of the benefits of participation may also play a role. To increase participation in the scheme and to address the quality of laboratory services throughout the region, AMREF is currently developing a Regional EQAS in collaboration with the Ministries of Health of Kenya, Tanzania and Uganda, in affiliation with the World Health Organisation (WHO). The approaches used to establish reference values for haemoglobin samples are discussed. The scheme has also been utilised to examine the performance of different techniques for haemoglobin estimation, demonstrating the inaccuracy of the visual comparator methods. Received: 13 April 2002 Accepted: 5 July 2002     

Performance of total reflection and grazing emission X-ray fluorescence spectrometry for the determination of trace metals in drinking water in relation to other analytical techniques

An intercomparison survey has been carried out in order to evaluate the performance of two related X-ray fluorescence techniques as compared to the achievements of several other analytical techniques applied for trace elements determination in drinking water. A relatively new technique, total reflection X-ray fluorescence (TXRF) and a novel related technique, grazing emission X-ray fluorescence (GEXRF) have been used for the analysis of a mineral water sample. The concentrations of the following elements have been determined: Na, Mg, K, Ca, Ni, Cu, Zn and Sr. The mineral water sample has also been analyzed by a number of other analytical techniques, routinely utilized in drinking water quality control. The analyses were performed in eleven laboratories which reported 286 individual determinations producing 75 laboratory means. From the obtained results, it can be concluded that the TXRF technique is suitable for a direct determination of heavy elements in drinking water (above potassium, Z = 19). This technique can compete with other analytical techniques routinely used in water quality monitoring. First results obtained with GEXRF spectrometry show that this technique can be successfully applied for the determination of low-Z elements in drinking water. However, results for sodium and magnesium were systematically too low, indicating that modifications of the quantification procedure may be required to improve the accuracy of determination for these light elements.     

Performance of total reflection and grazing emission X-ray fluorescence spectrometry for the determination of trace metals in drinking water in relation to other analytical techniques

An intercomparison survey has been carried out in order to evaluate the performance of two related X-ray fluorescence techniques as compared to the achievements of several other analytical techniques applied for trace elements determination in drinking water. A relatively new technique, total reflection X-ray fluorescence (TXRF) and a novel related technique, grazing emission X-ray fluorescence (GEXRF) have been used for the analysis of a mineral water sample. The concentrations of the following elements have been determined: Na, Mg, K, Ca, Ni, Cu, Zn and Sr. The mineral water sample has also been analyzed by a number of other analytical techniques, routinely utilized in drinking water quality control. The analyses were performed in eleven laboratories which reported 286 individual determinations producing 75 laboratory means. From the obtained results, it can be concluded that the TXRF technique is suitable for a direct determination of heavy elements in drinking water (above potassium, Z = 19). This technique can compete with other analytical techniques routinely used in water quality monitoring. First results obtained with GEXRF spectrometry show that this technique can be successfully applied for the determination of low-Z elements in drinking water. However, results for sodium and magnesium were systematically too low, indicating that modifications of the quantification procedure may be required to improve the accuracy of determination for these light elements. Received: 5 January 1998 / Revised: 17 February 1998 / Accepted: 18 February 1998     

Characterization (certification) of Corn Bran (NIST RM 8433), Corn Starch (NIST RM 8432) and Microcrystalline Cellulose (NIST RM 8416) Reference Materials for essential and toxic major, minor and trace elemental constituents

Summary Corn Bran (NIST RM 8433), Corn Starch (NIST RM 8432) and Microcrystalline Cellulose (NIST RM 8416) Reference Materials were characterized for essential and toxic major, minor and trace elemental composition in an interlaboratory cooperative characterization campaign. Extensive application of widely varied analytical methods by analysts in cooperating laboratories yielded 10–29 best estimate and 1–16 informational concentration values for each of these materials. Two materials, Corn Starch and Microcrystalline Cellulose, contain particularly low levels of trace elements. These reference materials are intended for analytical quality control of elemental determinations in corn and plant products as well as other agricultural/food materials with related matrices.Contribution No. 92–146 from Centre for Land and Biological Resources Research     

International Measurement Evaluation Programme: IMEP-9, trace elements in water

The International Measurement Evaluation Programme (IMEP) is an interlaboratory comparison scheme, founded, owned and coordinated by the Institute for Reference Materials and Measurements (IRMM) since 1988. IMEP-9 is the third round of trace elements in water evaluation following IMEP-3 and IMEP-6. Reference values for 15 elements stating total concentrations and combined uncertainties (according to GUM) were established. The reference values were established mainly by isotope dilution mass spectrometry (IDMS) as a primary method of measurement, and values traceable to the SI were obtained. The four elements that could not be certified by IDMS were assigned values by means of other measurement techniques. Results from 201 laboratories from 35 countries and four continents were evaluated against the reference values and the comparability between the laboratories is presented graphically.     

Evaluation of a proficiency test on cadmium and lead in herbal material using assigned reference values

This paper presents an international proficiency testing program (APLAC T065) on two trace elements, cadmium and lead, in an herbal sample, Herba Desmodii Styracifolii. The program was registered with a total of 109 laboratories from 42 countries. The assigned reference values of the analytes for performance assessment were provided by the organizers using an accurate gravimetric isotope dilution inductively coupled plasma-mass spectrometry technique. z-Score was used as the numerical indicator to interpret participants' competence. The between-laboratory variations for cadmium and lead were respectively 18.7% and 19.8% and the consensus values were found to be consistent with the assigned reference values. Twenty-two participants gave at least one unsatisfactory z-score, but the performance of the majority of participants on the analysis of cadmium and lead in herbal matrix was generally good when compared with the assigned reference values.     

IAEA quality control studies on determining trace elements in bioindicators

Twenty laboratories from 17 countries around the world participated in two analytical quality control exercises, coded NAT-5 and NAT-6, on determining trace and minor elements in plant bioindicator samples. 1398 laboratory mean values for 51 elements were submitted for two lichen and two moss materials. The submitted measurement results were evaluated as interlaboratory comparison (IC) exercises and as proficiency tests (PT) following standard procedures developed by the International Atomic Energy Agency (IAEA). The evaluations confirmed good performance of the participating laboratories for many elements. Furthermore, the laboratories performance based on IC criteria improved from the first exercise to the second one. Subsequent NAT-5 evaluation revealed systematic differences between the analytical values obtained non-destructively or after the total sample dissolution and the measurements following nitric acid sample dissolution (without the use of hydrofluoric acid) for some elements. The most critical elements for this kind of discrepancies appeared to be Al, Ca, Cr, Fe, Na, Ni, and Pb. After changing analytical methodologies in the concerned laboratories, more consistent values for those elements were obtained in NAT-6. This revised version was published online in August 2006 with corrections to the Cover Date.     

Intercomparison analysis of coal constituents—Learning by experience

A summary of the various exercises made in the BCR-framework to improve the quality of analysis of coal is given. The paper presents the way coal samples were prepared and their homogeneity as well as the analytical methods used by various participating laboratories. Special attention is given to the determination of sulphur and trace elements. A considerable improvement of results was obtained upon participation in such BCR-exercises.     

The Swiss External Quality Assessment Scheme in Bacteriology and Mycology 1992–1996

 The Swiss External Quality Assessment Scheme in Bacteriology and Mycology was created in 1980 and has been organised since 1983 by the Department of Medical Microbiology in Zurich. The number of Swiss participants has steadily risen from 66 in 1989 to 92 in 1996. Twelve bacterial and fungal strains are sent to the participants in four despatches, each containing three specimens, per year. Scores are allocated per specimen and range between 0 and 1. Participants with mean scores of ≤0.75 are considered poor performers. The mean scores increased from 0.85 in 1992 to 0.91 in 1996. This improvement can be attributed to the educational effect of the external quality control scheme, since all participants receive a detailed discussion for each specimen together with their individual results. On average, both large University and Cantonal (state) laboratories as well as private laboratories show satisfactory performance. In particular, laboratories officially recognised by the Swiss Federal Office of Public Health (SFOPH) rate better than non-recognised participants. Many small regional hospital laboratories, most of them not SFOPH-recognised, are often among the poor performers. They are often managed by technical staff and lack a trained microbiologist. The recently introduced legislation in Switzerland renders participation in external quality assessment schemes compulsory, and all clinical microbiology laboratories are required to employ qualified microbiologists. This will certainly help to improve the quality standards of all laboratories performing microbiological tests. Received: 13 November 1997 · Accepted: 28 December 1997     

Computer-aided quality assurance and certification of reference materials in the DANREF network

A network between 6 Danish laboratories with experience in quality assurance and quality control has been established with the aim of supporting the use and production of high-quality certified reference materials in Denmark. One of the tasks of the network was to develop a PC-program for computer-aided quality assurance and certification of reference materials produced by the network laboratories. This paper describes the design and features of the DANREF PC-program and shows examples of computer-aided evaluation of selected studies on reference materials. The program provides the network laboratories with the possibility to carry out harmonized statistical evaluation and documentation of homogeneity, stability and intercomparison studies in accordance with international guidelines and standards, e.g. ISO guide 35.     

Findings of national proficiency test exercise for the determination of trace elements in edible mushroom reference material

This paper presents the results of the proficiency test exercise conducted in Pakistan for the determination of trace elements in mushroom reference material. Thirteen laboratories from different organizations of the country submitted trace elemental data on Al, As, Br, Ca, Cd, Ce, Cl, Co, Cr, Cs, Cu, Fe, Hg, K, Li, Mg, Mn, Na, P, Pb, Rb Sc, Si, Sm, Sr, Th, Zn. Results for Al, As, Br, Ca, Cd, Cl, Co, Cr, Cs, Cu, Fe, K, Mg, Mn, Na, Rb Sc, and Zn, in the mushroom material were reported by two or more participating laboratories and could be subjected to statistical evaluation. The original data of these trace elements was subjected to a computer program “Histo Version 2.1” provided by IAEA. The four outlier tests, i.e., Dixon, Grubbs, skewness and kurtosis were applied to the data sets. Consensus (overall) mean values, absolute standard deviation, relative standard deviation, standard error, median and range of values for these elements have been reported at a significance level of 0.05.     

Certifying the chemical composition of a biological material — a case study

A worldwide laboratory intercomparison was organized by the International Atomic Energy Agency's Analytical Quality Control Services (AQCS) involving the determination of trace elements in plant materials used for human consumption. The National Institute of Standard and Technology (NIST) Standard Reference Materials Program donated 5 kg of spinach designated for the production of the future Standard Reference Material SRM 1570a to this intercomparison; the AQCS provided a similar amount of cabbage. For the study, 150 units of each material were distributed and 114 laboratories reported results on both materials to AQCS. The results for the spinach, encompassing more than forty elements, have been compiled and evaluated; estimates of the elemental concentrations were made based on statistical evaluations, principles of analytical procedures and the laboratory performance indicated by the results on the cabbage material. Satisfactory estimates were obtained for 27 elements. Comparison with IAEA laboratory and NIST reference data did not reveal any significant bias that might have been introduced by the intercomparison approach or its evaluation.     

The interlaboratory comparison "IMEP-19 trace elements in rice"—a new approach for measurement performance evaluation

The aim of IMEP is to present objectively the quality of chemical measurements. Participants in IMEP compare their reported measurement results with independent external certified reference values with demonstrated traceability and uncertainty, as evaluated according to international guidelines. IMEP-19 focused on measurements of trace elements in rice aiming to support the Commission Regulation (EC) No. 466/2001 on maximum levels for certain contaminants in foodstuff. Measurement results for the elements Cd, Cu, Pb and Zn were reported by 267 field laboratories involved in food analysis from 43 countries. Performance criteria for the evaluation of the reported measurement results in IMEP-19 are suggested. The chosen performance indicators not only take into account the deviation of the reported measurement value from the certified reference value, but also set criteria for maximum and minimum acceptable uncertainty. The IMEP-19 participants' performance is reviewed by means of using new simple graphical tools, called "Naji plots".     

Collaborative study for the quality control of trace element determinations in paint coatings Part 1. Interlaboratory study

Since the adoption of the European Standard EN71: Part 3 on toy safety, there has been dissatisfaction with the poor reproducibility obtained between laboratories using the test method for the determination of the migration of certain elements from paints to toys. This lack of quality control could result in toys being judged unacceptable with regard to the requirements of the EC Directive 88/378/EEC, which creates a potential barrier to trade. In order to improve the methods of measurements and testing, the Standards, Measurements and Testing Programme (SM&T) is currently supporting a project of which the final aim is to produce paint reference materials. The first step of this collaborative project is aimed to assess and possibly improve the state-of-the-art of trace element determinations in paint coatings through an interlaboratory study, the results of which are presented in this paper.