Interlaboratory Comparison Tests Research Articles

Neutron Activation Analysis: A Primary (Ratio) Method to Determine SI-Traceable Values of Element Content in Complex Samples

The metrological principles of neutron activation analysis are discussed. It has been demonstrated that this method can provide elemental amount of substance with values fully traceable to the SI. The method has been used by several laboratories worldwide in a number of CCQM key comparisons – interlaboratory comparison tests at the highest metrological level – supplying results equivalent to values from other methods for elemental or isotopic analysis in complex samples without the need to perform chemical destruction and dissolution of these samples. The CCQM accepted therefore in April 2007 the claim that neutron activation analysis should have the similar status as the methods originally listed by the CCQM as 'primary methods of measurement'. Analytical characteristics and scope of application are given.

A multiplex RT-PCR assay for the rapid and differential diagnosis of classical swine fever and other pestivirus infections

Classical swine fever is a highly contagious viral disease causing severe economic losses in pig production almost worldwide. All pestivirus species can infect pigs, therefore accurate and rapid pestivirus detection and differentiation is of great importance to assure control measures in swine farming. Here we describe the development and evaluation of a novel multiplex, highly sensitive and specific RT-PCR for the simultaneous detection and rapid differentiation between CSFV and other pestivirus infections in swine. The universal and differential detection was based on primers designed to amplify a fragment of the 5′ non-coding genome region for the detection of pestiviruses and a fragment of the NS5B gene for the detection of classical swine fever virus. The assay proved to be specific when different pestivirus strains from swine and ruminants were evaluated. The analytical sensitivity was estimated to be as little as 0.89TCID50. The assay analysis of 30 tissue homogenate samples from naturally infected and non-CSF infected animals and 40 standard serum samples evaluated as part of two European Inter-laboratory Comparison Tests conducted by the European Community Reference Laboratory, Hanover, Germany proved that the multiplex RT-PCR method provides a rapid, highly sensitive, and cost-effective laboratory diagnosis for classical swine fever and other pestivirus infections in swine.

Results of Stability Tests on Reference Materials Being Stored by JSAC, JSAC 0302, JSAC 0311, JSAC 0401, JSAC 0501, JSAC 0602-2, JSAC PT0711 and JSAC PT0721

In Mar. ’06 to May ’08, the Japan Society for Chemical Analysis has operated stability tests on seven reference materials being stored by JSAC : JSAC 0302-river water for the analysis of inorganic components, JSAC 0311-wastewater for the analysis of dioxins, and so on. Interlaboratory comparison tests were performed with the participation of 6 laboratories for each reference material. In the tests, reference materials in storing were analyzed for the same components as in their certification or assignation. En numbers defined in ISO Guide 43-1 and En' numbers that derived from En were calculated from the test results and certified/assigned values in order to quantify the deviation of test results from the certified/assigned values. The stability of a reference material can be evaluated through the absolute value of its En' number. As a result, almost all results of stability tests of every reference material showed good relations with their certified/assigned values. Therefore, it was concluded that the reference materials tested here were stable.

Bluetongue virus: European Community inter-laboratory comparison tests to evaluate ELISA and RT-PCR detection methods

European Community national reference laboratories participated in two inter-laboratory comparison tests in 2006 to evaluate the sensitivity and specificity of their ‘in-house’ ELISA and RT-PCR assays for the detection of bluetongue virus (BTV) antibodies and RNA. The first ring trial determined the ability of laboratories to detect antibodies to all 24 serotypes of BTV. The second ring trial, which included both antisera and EDTA blood samples from animals experimentally infected with the northern European strain of BTV-8, determined the ability of laboratories to detect BTV-8 antibodies and RNA, as well as the diagnostic sensitivity of the assays. A total of six C-ELISAs, six real-time RT-PCR and three conventional RT-PCR assays were used. All C-ELISAs were capable of detecting the BTV serotypes currently circulating in Europe (BTV-1, 2, 4, 8, 9 and 16), however some assays displayed inconsistencies in the detection of other serotypes, particularly BTV-19. All C-ELISAs detected BTV-8 antibodies in cattle and sheep by 21 dpi, while the majority of assays detected antibodies by 9 dpi in cattle and 8 dpi in sheep. All the RT-PCR assays were able to detect BTV-8, although the real-time assays were more sensitive compared to the conventional assays. The majority of real-time RT-PCR assays detected BTV RNA as early as 2 dpi in cattle and 3 dpi in sheep. These two ring trails provide evidence that national reference laboratories within the EC are capable of detecting BTV antibodies and RNA and provide specificity and sensitivity information on the detection methods currently available.

The renewed airflow standard system in Japan for 5–1000 m 3/h

The airflow standard system in Japan for the middle range (5–1000 m 3/h) has been renewed since 2002. The constant volume tank to realize the standard was replaced to have better performance at higher pressure, although its principle is exactly the same as its predecessor. Otherwise, most hardware for the system is unchanged, however the software for controling the measurements is improved to give the capability for tele-calibration on a unique basis. The facility also has a unique time measurement system based on analog-to-digital (A/D) conversion to analyze instantaneous behaviors of flowmeters. This paper describes the outline of the renewed standard system together with some results from inter-laboratory comparison tests, in which very good consistency of the renewed system with other facilities, including its own predecessor, are shown.

Preparation and Certification of New Reference Materials, Combustion Dust (JSAC 0511 and JSAC 0512) for Determination of Dioxins

The Japan Society for Analytical Chemistry has developed two new certified reference materials (CRMs) for analyses of dioxins (polychlorodibenzo-p-dioxins and polychlorodibenzofurans) and coplanar polychlorobiphenyls. A project team was organized to prepare two kinds of combustion dust and to certify the concentration of dioxins and polychlorobiphenyls. An interlaboratory comparison test was performed by participants from 23 laboratories. In a statistical analysis, z scores in a robust method were applied to reject outliers, followed by the usual statistical procedure. The presented CRMs are expected to be useful for the quality assurance and the quality control of dioxins analysis.

Evaluation of Results of an Interlaboratory Comparison Test on Determination of Acrylamide in Crispbread Samples

The European Commission's Directorate General Joint Research Centre has organized several proficiency tests on the determination of acrylamide (AA) in food. This paper presents the results and outcome of a proficiency test that focused on the determination of AA in crispbread samples. One of the goals was the identification of the influence of different parameters such as analyte extraction or instrument calibration on the analytical results. A set of samples, containing 3 different crispbread samples as well as extracts of one crispbread sample and AA standard solutions, was shipped to each participant. A total of 42 European laboratories reported analytical results that were evaluated by applying internationally accepted protocols and procedures. The study found that, for each sample, the results of 4-8 laboratories were outside the range formed by the target value plus or minus the 2-fold of the target standard deviation; thus, they did not perform satisfactorily. In transferring this knowledge to the data of monitoring databases of AA in food, care must be taken that data are quality controlled, as it is likely that some of them may be biased.

Preparation and Certification of the Reference Materials, Marine Sediment for the Determination of Dioxins and Polychlorobiphenyls

The Japan Society for Analytical Chemistry has developed two new certified reference materials (CRMs) for dioxins: coplanar PCBs and 1 ~ 10 chlorinated PCB homologues. A project team has been organized to prepare 2 kinds of marine sediment and to certify the concentration of dioxins and polychlorobiphenyls. An interlaboratory comparison test was performed by participants from 24 laboratories. In a statistical analysis, the z scores in robust method were applied to reject outliers, followed by the usual statistical procedure. The presented CRMs are expected to be useful for the quality assurance and quality control of dioxins analysis.

Confirmation of Synthetic Glucocorticoids with Liquid Chromatography/Mass Spectrometry: Organization and Results of an International Interlaboratory Comparison Test

Within the framework of a European Union (EU) research project entitled "Food Safety Screening: Synthetic Glucocorticoids (QLK1-1999-00122)," an international interlaboratory ring test was organized to compare and evaluate different liquid chromatography/mass spectrometry (LC/MS) confirmatory methods that are applied in European monitoring programs for detecting the use of synthetic glucocorticoids. Liver and urine samples of bovines treated with synthetic glucocorticoids were collected and sent to the participants of the study for analysis. Participants received 3 liver and 3 urine samples and were free to use either their own LC/MS method or an LC/MS-based method developed during the EU research project. The residue concentrations in the samples were calculated as the mean of the concentrations reported by each laboratory. The mean dexamethasone concentration of liver sample L1 was calculated as 2.27 microg/kg [relative standard deviation (RSD) 43%, n = 9], which exceeds the maximum residue level (MRL) of 2 microg/kg. Three of the 9 laboratories (33%) reported concentration levels less than 2 microg/kg, resulting in obviously false compliant results. The overall mean concentration of flumethasone in liver sample L2 was calculated as 3.27 microg/kg (RSD 33%, n = 8). Applying a comparable limit for flumethasone of 2 microg/kg, 8 of the 9 laboratories would have obtained a correct noncompliant result. As for the blank liver sample, 1 participant found a false noncompliant result. The urine sample U1 contained prednisolone residues at a mean concentration of 1.58 microg/kg (RSD 43%, n = 9). Four out of 9 results were less than a theoretical minimum required performance level (MRPL) of 2 microg/kg. The calculated concentration of dexamethasone in urine sample U3 was 5.21 microg/kg (RSD 62%, n = 9). One of the 9 results was lower than 2 microg/kg. Urine sample U2 was correctly reported as blank by all participants.

Results from Two Interlaboratory Comparison Tests Organized in Germany and at the EU Level for Analysis of Acrylamide in Food

After the publication of high levels of acrylamide (AA) in food, many research activities started all over the world in order to determine the occurrence and the concentration of this substance in various types of food. As no validated methods were available at that time, interlaboratory studies on the determination of AA in food were of the highest priority. Under the boundary conditions of applying well-established evaluation schemes, the results of 2 studies conducted by the Federal Institute for Risk Assessment (BfR) in Germany and by the European Commission's Directorate General Joint Research Center (JRC) exhibited an overall acceptable performance of the participants in these studies. Nevertheless, many laboratories showed problems in determining AA in food with a complex matrix such as cocoa. The results of analysis also showed a broader variation of AA for samples with low AA concentrations and indicated a bias of the results obtained by gas chromatography-mass spectrometry without derivatization. Improvements of the performance of some laboratories appeared to be necessary.

Quality management in reference tests for the diagnosis of classical swine fever

Inter-laboratory comparison tests for the diagnosis of classical swine fever (CSF) have been established by the national swine fever laboratories of European Union (EU) Member States. They provide a method of measuring both the quality of the results of diagnostic tests performed by laboratories and the competence with which they were performed. The objective is that all laboratories obtain the same result when investigating the same sample. This study evaluates the results of serological and virological reference tests for CSF (neutralisation test and virus isolation) performed over a period of three years. The sensitivity of the serological diagnosis for the detection of CSF antibodies was very good and revealed a tolerance limit of the scored antibody titres of one dilution step. Results on the same sample in two consecutive years were similar. The variation of the scored antibody titres was larger when testing sera with a low CSF antibody titre. The interpretation of the antibody titres as 'CSF positive or negative' was only slightly altered by these variations. The backtitration of a neutralisation test (used as a control measure) is a more mathematical value which does not correlate directly with the biological system. Commercial CSF antibody enzyme-linked immunosorbent assays still display a lower sensitivity on individual samples compared to the reference neutralisation test. Classical swine fever virus isolation was well established in all participating laboratories and caused very few problems. Specificity of CSF diagnosis by investigating CSF antibody and CSF virus negative sera was not problematic either. In general, the reference tests for CSF diagnosis are well established in the EU. They are based on living systems, e.g. cells and virus, and consequently they have a different tolerance limit than pure mathematical values. What is important is that the interpretation of the test result is identical in all laboratories.

Preparation and certification of new reference materials Forest soils (JSAC 0421 and JSAC 0422) for the determination of dioxins

The Japan Society for Analytical Chemistry has developed two new certified reference materials (CRMs) for dioxins and coplanar PCBs. A project team was organized to prepare 2 kinds of forest soil and to certify the concentration of dioxins. An interlaboratory comparison test was performed with the participation of 15 laboratories. In a statistical, analysis, z-scores in the "robust method" were applied to estimate the degree of bias of reported data from the mean value in order to reject any data with a big bias, and was followed by the usual statistical procedure. The presented CRMs are expected to be useful for the quality assurance and quality control of dioxins analysis.

Preliminary study to prepare a reference material of styrene metabolites - mandelic acid and phenylglyoxylic acid - in human urine

A preliminary batch of the reference material was prepared by freeze-drying pooled urine samples obtained from healthy persons occupationally exposed to styrene. Tests for homogeneity and stability were performed by determining urine concentrations of mandelic (MA) and phenylglyoxylic acids (PGA). The urinary MA and PGA concentrations were followed over an 8-month period using high performance liquid chromatography (HPLC). No changes of the concentration values were found. Pure PA and PGA from Merck and Fluka, respectively, were used for traceability purposes, because certified or standard reference materials for MA and PGA do not exist. Control material ClinChek-Urine Control (Recipe) was analysed simultaneously. The mean values of MA and PGA compared well with the means of control samples and fell within the control range. The certified values and their uncertainties were evaluated from the results of interlaboratory comparisons, homogeneity (277.0 ± 7.4 mg L−1 for MA and 148.0 ± 4.7 mg L−1 for FGA) and stability tests. The values are unweighted arithmetical averages of accepted results and their uncertainties are combined uncertainties enlarged by coefficient k=1, evaluated from the standard uncertainties of the interlaboratory comparison, homogeneity and stability tests.

INTER-LABORATORY COMPARISON OF PLANT ANALYSIS ACCURACY IN MEXICO

Laboratories seeking accreditation based on norm ISO 17025 are requested to satisfy several requirements such as: traceability of measurements (i.e., the use of certified reference material linked to SI units), participation in inter-laboratory comparison or proficiency testing programs, and determination of the uncertainty of the measurements. One of the objective of the present work was to evaluate the accuracy of analytical measurements conducted by Mexican soil and plant analytical facilities, using certified reference material as recommended by the metrological methods. The statistics used to evaluate the accuracy was the Mean Square Error as recommended by The Mexico's Metrological National Center (CENAM). Most laboratories did not produce reliable results. It is important to have long term programs like this and more reference materials available to achieve better accuracy. The results of the intercomparison exercises allowed to identify the laboratories that generate reliable results.

Quality Assurance and Quality Control in Diagnostic Molecular Biology

The newest forms of clinical diagnostic testing are based upon tools gleaned from molecular biology. Manipulations of RNA and DNA from various tissue sources (e.g., skin, blood, urine, excised tumor) can provide valuable information about an individual's genetic status or the basis or potential for metastasis of a tumor. As of 2002, over 200 laboratories in the United States provide clinical services. Particularly when such information is to be used to provide genetic counseling or determine treatment, care must be taken to ensure accuracy in the generation and reporting of results. This unit outlines the aspects of quality assurance that are important in nucleic acid-based diagnostic testing. More specifically, it describes the three elements of a quality assurance program: the directors qualifications, on-site laboratory inspection, and interlaboratory comparison and proficiency testing. The unit also discusses how to evaluate if a particular genetic test is suitable for clinical testing.

Fehlende Präzisionsdaten ermitteln

In the context of the DIN EN ISO/IEC 17025 standard the interest in materials testing is focusing again on precise data. This paper describes a procedure by which plausible precise data can be calculated from insufficient data of interlaboratory comparison tests by the help of additional information. Such calculations made obvious that insufficient precise data cannot be excluded a priori in respective standards and that the assessment of result uncertainties can be significantly influenced by unknown subjective effects during testing.

Determination of zearalenone in grains by high-performance liquid chromatography–tandem mass spectrometry after solid-phase extraction with RP-18 columns or immunoaffinity columns

In this paper a robust, sensitive and selective LC–MS–MS method for the determination of zearalenone (ZON) in several cereals is described. Sample preparation was performed by extraction of the commodities with a mixture of acetonitrile and water followed by solid-phase extraction with RP-18 columns or immunoaffinity columns. The selective determination of ZON was achieved with an atmospheric pressure chemical ionization interface. Using the negative ion mode a detection limit of 0.5 μg/kg and a determination limit of 1 μg/kg grain was achieved, which is by a factor of 100 more sensitive than the positive ion mode. Zearalanone (ZAN), which does not occur in nature, was used as internal standard for quantification. A linear working range from 1.0 μg/kg to 1000 μg/kg could be achieved in grains with a standard deviation of 4% and recovery rates around 100%. All these results were independent from the grain matrices (maize, barley, oats, wheat) when ZAN was used as internal standard. Sample preparation with RP-18 and immunoaffinity materials gave comparable results. In addition, the method was successfully used for the investigation of naturally contaminated maize samples in the course of an interlaboratory comparison test.

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.

Interlaboratory comparative tests in the system for accrediting analytical laboratories

Interlaboratory comparative tests ICT are used for checking the technical proficiency of laboratories during accreditation or inspection under the system for accrediting analytical laboratories or centers. The main tasks are formulated for the metrological support to these tests handled by ICT.

Quality assurance in analytical measurement

The peculiarities of analytical measurement require to check characteristics of the error (its components) of the obtained analysis results to assure the quality of the measurements. This article deals with the various quality assurance procedures and algorithms which are used to check the quality indices, i.e. the accuracy, reproducibility, certainty and repeatability of analytical measurements: These procedures include: laboratory rapid control; Intra-laboratory statistical control (statistical selection control by alternative attribute, statistical selection control by quantity method of periodic check of the analysis procedure for conformity to the specified requirements) and external control (inter-laboratory control checks, inter-laboratory comparison tests, and intra-laboratory control algorithms carried out by the appropriate supervisory body.) in the separately taken laboratory. The respective algorithms, control plans and control requirements, specified according to the different control aims and assurance tasks, enable the quality and certianty of analytical information obtained in laboratories in Russia to be assured.