Interlaboratory comparison study for the determination of halogenated hydrocarbons in water

Sixty laboratories of five different countries participated in a large-scale interlaboratory comparison test for the determination of halogenated hydrocarbons in water. Participants used their in-house method with 44 laboratories applying head space GC ECD analysis and 5 using liquid/liquid extraction. A set of two artificially produced samples was prepared; the halogenated hydrocarbons investigated were trichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, trichloromethane, tetrachloromethane, 1,1-dichloroethylene, dichloromethane, dibromochloromethane, bromodichloromethane, 1,2-dichloroethane and tribromomethane. The procedure of sample preparation, storage and distribution was monitored by an extensive quality assurance system including homogeneity tests, stability tests, and trend analysis of the submitted data. The analytical results submitted by the participants exhibited RSD values of up to 35% and outlier rates of up to 19%. The percentage of false positive and false negative results was at the highest 12% for selected substances. Recovery rates varying from 86% to 106% proved the correctness of the analytical results submitted by the participants and showed that the procedure developed in this study for sample preparation and distribution is well suited for the performance of large-scale interlaboratory comparison tests of halogenated hydrocarbons in water. Received: 7 December 1998 / Revised: 23 March 1999 / Accepted: 24 March 1999     

Physiological reference values: a shared business? Report of the second European symposium on clinical laboratory and in vitro diagnostics industry

The Catalan Association of Clinical Laboratory Sciences, with the support of its corporative members, organized the second European symposium devoted to physiological reference values, in Barcelona. The objectives were: (i) to discuss ways to develop a common strategy among clinical laboratories and the in vitro diagnostic (IVD) industry for the generation of physiological reference values related to biological quantities of medical interest; and (ii) to establish consensus between both groups regarding the interpretation of the requirements related to physiological reference values contained in the European (EU) Directive 98/79-EC and in the EN-ISO 15189:2003 standard. The symposium was divided into four parts in which different aspects of the reference values were discussed: legal and normative aspects, alternatives to the production of own reference values, methodology, and diffusion and teaching. The main conclusions were the need to clarify the requirements described by the EU Directive 98/79-EC and EN-ISO 15189:2003 regarding reference values, and the need for cooperation between industry, clinical laboratories, and health authorities to achieve common reference intervals, including multicentric reference intervals.     

Quality issues in proficiency testing

 Proficiency testing is a means of assessing the ability of laboratories to competently perform specific tests and/or measurements. It supplements a laboratory's own internal quality control procedure by providing an additional external audit of their testing capability and provides laboratories with a sound basis for continuous improvement. It is also a means towards achieving comparability of measurement between laboratories. Participation is one of the few ways in which a laboratory can compare its performance with that of other laboratories. Good performance in proficiency testing schemes provides independent evidence and hence reassurance to the laboratory and its clients that its procedures, test methods and other laboratory operations are under control. For test results to have any credibility, they must be traceable to a standard of measurement, preferably in terms of SI units, and must be accompanied by a statement of uncertainty. Analytical chemists are coming to realise that this is just as true in their field as it is for physical measurements, and applies equally to proficiency testing results and laboratory test reports. Recent approaches toward ensuring the quality and comparability of proficiency testing schemes and the means of evaluating proficiency test results are described. These have led to the drafting of guidelines and subsequently to the development of international requirements for the competence of scheme providers. Received: 2 January 1999 · Accepted: 7 April 1999     

External quality assessment schemes for clinical laboratories

 The clinical routine laboratory generally utilizes cheap, easy and rapid measurement procedures ("methods") in order to meet the requirement for the production of many analytical results (500–3000 per day) of hundreds of different types. The measurement procedures are optimized for the analysis of native patients' samples, but are frequently sensitive to deviation of the composition of the matrix from that in normal fresh samples. The inherent lack of stability of patient samples means that control samples need to be stabilized. The method of stabilization is critical. Furthermore, the method of "spiking" samples with pathological material is a matter of concern. Generally, minimally processed patients' samples should be used in external quality assessment (EQA) schemes. Consensus values are currently the most popular for use as a guide to the best results from participating laboratories in EQA schemes; these often work fairly well. However, the uncertainty and traceability of this type of value is unknown, and in some cases may even be misleading, tending to preserve bad routine methods when these are dominant in the participating laboratories. Reference measurement procedure (RMP) values are recommended to provide scientifically based information, to facilitate the proper choice of methods in the routine laboratories, and to validate the suitability of control materials in EQA schemes. The present paper provides selected examples from a study comparing consensus values with RMP values on lyophilized sera, and also presents results on a fresh frozen thawed serum for the study of commutability. Received: 8 November 1995 Accepted: 8 May 1996     

External quality assessment in microbiology: comparison of results from Belgian and Canadian laboratories with regard to their ability to identify <Emphasis Type="Italic">Streptococcus pyogenes</Emphasis>

Clinical Microbiology Proficiency Testing (CMPT; Canada) and the Institute of Public Health (IPH; Belgium) set up a joint external quality assessment (EQA) project in which they sent identical simulated clinical samples to their respective participants. Samples were sent out as throat swabs containing Streptococcus pyogenes (as pathogen) and viridans streptococci (as commensal). Results from identification by the Belgian laboratories were excellent: 99.5% detected the group A streptococci. About 10% of the Canadian laboratories reported the absence of reportable β-haemolytic streptococci, although for most of them the issue was one of non-examination of small or pin-point streptococci. Overall, Canadian and Belgian laboratories performed well in this EQA; the joint project clearly showed that although many similarities exist, there are differences between laboratories in treating EQA samples and reporting results.     

The European way to go: Virtual Central Laboratory

In clinical pharmaceutical trials often one central laboratory is used for the analysis of routine parameters, the so-called safety parameters. In many countries the heads of laboratory departments question the quality of such analysis in terms of quality of samples after transport, continuity of patient related medical laboratory information before, during and after the trial; turn around time; alerting procedures and consultancy to requesting physicians. On the other hand, the pharmaceutical industry prefers to work with central laboratories since they can claim certification or accreditation. Also the use of one set of reference values is an important issue, as well as electronic data transfer to the trial organizer's database. The concept of a Virtual Central Laboratory (VCL), initiated in the Netherlands, tries to solve this conflicting situation. In the concept, local hospital laboratories receive computer-assisted aid in the identification of patients, trials, visits and requests. The laboratory data are transformed using calibrator sets to produce a homogeneous data set across laboratories, resulting in one set of reference values. The data are electronically transferred to a central computer from which they are send in any desired format to the trial organizer's database. Participating laboratories are obliged to work towards accreditation. The VCL acts as a central counterpart for both the pharmaceutical industry and local laboratories. The concept offers advantages to the pharmaceutical industry, the investigator and local laboratories.     

Definition of assigned values for proficiency tests in water analysis

The definition of an assigned value is usually achieved by calculating mean values from the data (with different methods) or by designating reference laboratories. Neither method is completely satisfactory. In this paper a new method is presented for the definition of the assigned value for spiked samples with an unknown content of the analyte in the matrix. The method consists of two parts. The first is the estimation of the assigned values from the spiked amounts and the content in the matrix, based on the results of reference laboratories. The other is the designation of these reference laboratories by comparing their results with the assigned values. Because each of these parts requires the other, an iterative procedure is necessary. As an example, the results of a proficiency test for the analysis of copper in wastewater are used to compare the calculated values with those from other methods, e.g., the Huber estimation. Received: 25 September 2000 Accepted: 9 December 2000     

A critical comparison of on-line coupling IC-ICP-(AES, MS) with competing analytical methods for ultra trace analysis of microelectronic materials

On-line coupling of ion chromatography and atomic spectrometry (IC-ICP-(AES, MS)) are compared to so-called reference methods and other competing methods for ultra trace characterization of solid microelectronic materials. The comparison is based on analytical data gained for well characterized samples by a number of different laboratories. The matrices used for comparison are Mo, Mo-oxide, MoSi_x, W, W-oxide, WSi_x, metallic As, red P and Re. The analyte elements accessible by IC-ICP-(AES, MS) and with reference values for at least one other method are Ag, Al, Ba, Ca, Cd, Cr, Co, Cu, Fe, K, Mg, Mn, Na, Ni, Ti, Tl, Th, U and Zn. The agreement of results of IC-ICP-(AES, MS) with those of isotope dilution mass spectrometry (IDMS) and radiochemical activation analyses (RNAA) shows good accuracy for most elements and some contamination problems with ubiquitous elements. A correlation of IC-ICP-(AES, MS) and GDMS results is undoubtful, but the discrepancies are rather high. As further technique ETV-ICP-MS is compared, whose results are in reasonable agreement with IC-ICP-(AES, MS). Details on some new applications as well as of some new methodological enhancements of on-line coupling IC-ICP(AES, MS) for the matrices As and P were included. Received: 8 December 1998 / Revised: 23 March 1999 / Accepted: 28 March 1999     

Simultaneous determination of p-phenylenediamines and aminophenols in hair dye products: interlaboratory study

An isocratic HPLC method routinely used in the National Laboratory for Food and Drug Analysis of Taiwan was validated for the simultaneous determination of six aminophenols and phenylenediamines in commercial hair dyes. After extraction of the commercial hair dye product, the dye intermediates were determined by HPLC. Recoveries from the extraction were between 91.6 and 96.5%. The method was then evaluated in an interlaboratory collaborative study according to AOAC guidelines. Five laboratories in Taiwan participated in the study that analyzed the test product, which was preanalyzed by two laboratories to ensure acceptable homogeneity. The RSD(r) and RSD(R) values of the measurements obtained for the dye intermediates in the product were < or = 3.75 and < or = 5.95%, respectively. The method demonstrated acceptable reproducibility, as evidenced by HorRat values of 0.82- 0.97. The applicability of the method to the determination of oxidative hair dye components was further demonstrated in analyses of two different products. The method is thus proposed to be used by manufacturers and laboratories to evaluate the quality of commercial hair dyes containing the six aminophenols and phenylenediamines.     

Performance evaluation of polycyclic aromatic hydrocarbons analysis in sediment from proficiency testing with metrological reference values

This paper describes a metrological approach to evaluate the measurement capability of laboratories participating in two proficiency testing (PT) programmes involving the analysis of five polycyclic aromatic hydrocarbons (PAHs) in sediment samples. Reference values of PAHs in the programmes for performance assessment were obtained from an accurate isotope dilution gas chromatography mass spectrometry (ID-GCMS) method which was thoroughly validated and verified. Isotope dilution mass spectrometry (IDMS) technique usually has a well-defined measurement uncertainty budget and a traceability link to an International System of Units. Provision of the metrological reference values in PT enables the establishment of a technical platform to assess the actual competence of the participating laboratories in sediment PAHs analysis. Results of the PT programmes showed that about 80 % of the laboratories employed gas chromatography in their analyses and the remaining used liquid chromatography. Irrespective of the techniques being used, however, the majority of the participating laboratories were observed to underestimate values in which the mean values of the five reported PAHs were less than those of the ID-GCMS-derived reference values by 13–20 %. Only 41–44 % of the participating laboratories were able to achieve satisfactory z-scores. The present study revealed that the reinforcement of the capability for accurate measurement of PAHs in sediment samples in laboratories worldwide should be addressed.     

Performance of Canadian clinical laboratories processing throat culture proficiency testing surveys

Proficiency testing results obtained from simulated throat swab cultures sent between 1999 and 2013 were analyzed to evaluate the ability of participants to process, analyze, and properly report results for these cultures. Eight percent of all pathogen-positive samples were reported as false negatives, and 11 % of the pathogen-negative ones were reported as false positives. More than 90 % of the participants achieved acceptable grades in each of the proficiency testing samples containing Streptococcus pyogenes. Laboratories were less successful in reporting other significant pathogens including group C and G streptococcus and Arcanobacterium haemolyticum, although an overall increase in performance was observed for each subsequent survey. Most laboratories recognized other respiratory pathogens as not being agents of pharyngitis; a common issue with these specimens was the suggestion of the organism’s clinical significance when their presence was reported. The presence of small colony-forming β-hemolytic streptococcus (Streptococcus anginosus group) proved to be challenging for many laboratories as 66 % of all unacceptable grades for pathogen-negative throat swabs occurred in these PT samples. Moreover, performance in this group did not improve with subsequent surveys. Results obtained in this study support the added value of clinical relevancy challenges for proficiency testing as laboratories that may not have problems with the analytical aspect of the testing process struggle with the appropriate interpretation of results.     

Abundance ratios of mercury isotopes by 6s6p3P1-intermediate state excitation with resonance ionization mass spectrometry

The isotope-selective excitation of mercury via the 6s6p ³ P ₁ intermediate state excitation is studied with two-color resonance ionization mass spectrometry to determine abundance ratios of stable mercury isotopes. Lifetime, isotopic shifts, and hyperfine structure (HFS) splittings are measured. Atomic hyperfine interaction constants are determined. Line strengths of the ten components of the 6s ^{2 1}S₀→ 6s6p ³ P ₁ transition are used for isotope ratio determinations. Ion signal intensities of even-mass components directly give the isotopic abundance, in contrast to the odd-mass components, for which the sum of the HFS components results in an anomalously high response for the isotopic abundance. The laser bandwidth dependence of the excitation and population probabilities of magnetic HFS sublevels due to linear polarization of the radiation are discussed. These considerations yield reasonable values for the apparent odd-mass isotope abundance. Received: 13 November 1998 / Revised: 18 January 1999 / Accepted: 21 January 1999     

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     

Pesticide analysis in ground water. Statistical evaluation of certification data of a multicomponent reference material

21 laboratories participated in the certification of a multicomponent ampouled reference material containing 24 pesticides. This paper describes the statistical analysis of the unbalanced data set returned by the participants in the certification. The simplest method of certification is achieved when laboratories report all the required data. In practice, however, with complex analytical methods such as multicomponent analyses of organic compounds, laboratories are not able to report all the required data. The response for each determinand in the material has been modelled in a three-factor nested model. For computational comfort the model has been rephrased into a general linear model. The statistical problems with unbalanced data are discussed in relation to ISO 5725 and ISO Guide 35. Tests for homogeneity are exact and uninfluenced by the unbalance in data. Unbalanced data cause dependencies between mean squares above the second lowest level of the model, thus exact hypothesis testing is not possible at higher levels. Approximate tests for variation between rounds and laboratories has been constructed by means of Satterthwaite’s formula [1]. A graphical plot of deviances from certified values has been applied to illustrate laboratory performance. Received: 25 May 1997 / Revised: 6 December 1997 / Accepted: 15 January 1998     

An Interlaboratory Comparison of a Standardised EDTA Extraction Procedure for the Analysis of Available Trace Elements in Two Quality Control Soils

Abstract

A standardised EDTA extraction procedure was tested collaboratively by six laboratories using two in-house reference soils identified as soil A and soil B. The extracts were analysed for Zn, Cu, Pb and Mn by Inductively Coupled Plasma Spectrometry. Concentrations of extractable elements in soil A were generally much lower than those found in soil B. All laboratories produced some extreme outlying results, most of these were produced in soil B. Results for Mn were the most variable, with a range of 63.4–100.3 μg g^?1 in soil A and 226.4–415.3 μg g^?1 in soil B. In both soils, one laboratory reported high values for Zn and Mn and, one laboratory, for soil B, produced values for all four elements which were consistently low.

If outlying results are ignored, the results from most laboratories were in reasonable agreement for all elements except Mn.     

Measurement of sugar content by multidimensional analysis and mid-infrared spectroscopy

The advent of more and more powerful micro-computers has allowed the introduction of multidimensional analysis in research laboratories. Complex mathematical treatments are now possible within a few seconds. Prediction equations that linked sucrose, fructose, glucose, total sugars and reducing sugars concentrations to the spectral data, were established by regression on the principal components. Very high correlation coefficient values between the first ten axes and the chemical values were obtained. The bias and standard deviation (S.D.) values obtained between reference and predicted values were good. From such aqueous biological samples containing a ternary mixture of sucrose, fructose and glucose it was possible to (i) identify the characteristic IR bands of these different sugars (and their combination: reducing sugars, total sugars)-using spectral pattern; and (ii) to specifically measure their concentrations with good accuracy.     

Initial Results From the Non-Methane Hydrocarbon Intercomparison Experiment

The Non-Methane Hydrocarbon Intercomparison Experiment (NOMHICE) is described. This experiment has been designed to evaluate analytical techniques currently being used by scientists throughout the world to measure ambient atmospheric hydrocarbon concentrations. NOMHICE consists of a series of planned experiments designed to identify existing problems in participating scientist's laboratories and to correct them. The various experimental steps (or phases) have been scheduled in order of increasing complexity so that problems can be addressed as they arise. Results are presented for the initial phases of this program. Phase 1 involved the circulation of a 2 component gravimetrically prepared standard to 40 laboratories throughout the world. Participants were asked to quantify but not identify the components. Phase 2 involved the circulation of a more complex 16 component gravimetrically prepared mixture to 32 participants. Participants were asked to identify and quantify the components. Further tasks are described which will be carried out in the future.     

An error model for evaluation and interpretation of proficiency testing

Data from proficiency testing can be used to increase our knowledge of the performance of populations of laboratories, individual laboratories and different measurement methods. To support the evaluation and interpretation of results from proficiency testing an error model containing different random and systematic components is presented. From a single round of a proficiency testing scheme the total variation in a population of laboratories can be estimated. With results from several rounds the random variation can be separated into a laboratory and time component and for individual laboratories it is then also possible to evaluate stability and bias in relation to the population mean. By comparing results from laboratories using different methods systematic differences between methods may be indicated. By using results from several rounds a systematic difference can be partitioned into two components: a common systematic difference, possibly depending on the level, and a sample-specific component. It is essential to distinguish between these two components as the former may be eliminated by a correction while the latter must be treated as a random component in the evaluation of uncertainty. Received: 20 November 2000 Accepted: 3 January 2001