Interlaboratory study of the Charm ROSA Safe Level Aflatoxin M1 Quantitative lateral flow test for raw bovine milk

An interlaboratory study of 21 public health, state agriculture, and industry laboratories in the United States tested raw commingled bovine milk containing aflatoxin M1 using the Charm Rapid One Step Assay (ROSA) Safe Level Aflatoxin M1 Quantitative lateral flow method. Blind coded sample pairs were fortified with 0, 300, 350, 400, 450, 500, and 550 parts per trillion (ppt) aflatoxin M1. A ROSA reader quantitatively interpreted test strips with ppt readings. Readings < or = 400 ppt were interpreted as negative, and readings >400 ppt were interpreted as positive. Initial positive samples were subsequently assayed 2 additional times. If both retest results were >400 ppt, the sample was called positive/ actionable relative to U.S. and Codex levels, 500 ppt. The concentration of 400 ppt was chosen for the positive/negative interpretation to provide 90% sensitivity with 95% confidence at the 500 ppt legislative level. The combined false negative rate was <5% (4 of 83) for samples at 500 and 550 ppt. The false violatives at 0, 300, 350, 400, and 450 ppt (n = 42 at each level) were 0, 0, 21, 14, and 93%, respectively. The 90% positive concentration with 95% confidence was 503 ppt by probit analysis. The average intralaboratory repeatability was 11% and average interlaboratory reproducibility was 13% for the fortified sample pairs. High-performance liquid chromatography analysis of the study samples by 5 laboratories showed 38% false negatives with the 500 and 550 ppt samples, and a 0% false-violative rate with samples less than the 500 ppt action level.     

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 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     

Comparison of enzyme-linked immunosorbent assay with liquid chromatography-tandem mass spectrometry for the determination of diethylstilbesterol residues in chicken and liver tissues

A competitive enzyme-linked immunosorbent assay (ELISA) was developed for the quantitative detection of the diethylstilbesterol (DES). Polyclonal rabbit antisera, raised against protein conjugate diethylstilbesterol-mono-caroxyl-propyl-ethyl-bovine-serum-albumin (DES-MCPE-BSA), were utilized in immobilized antibody-based and competitive immunoassays. Assay conditions, including concentrations of antisera and horseradish peroxidase, (HRP)-DES, were optimized. The effects of incubation time, surfactant concentration, ionic strength and pH of the medium were also investigated. The typical calibration curve gave an average IC(50) value of 2.4 ng/mL, calibration range from 0.2 to 30.5 ng/mL and a detection limit of 0.07 ng/mL. The specificity of the assay was tested against DES structurally related compounds, and the assay proved highly selective for DES. Assay performance was validated using spiked chicken meat and liver tissue samples. Moreover, it was compared with liquid chromatography-tandem mass spectrometry. The ion pair for quantification of DES was m/z 267.4/251.4, and the linear equation of DES was y = 0.1033x + 0.0126 (r = 0.9960). The two analytical methods can be applied to monitor DES and other steroid residues in foods.     

Reference values of urinary 3,5,6-trichloro-2-pyridinol in the Italian population--validation of analytical method and preliminary results (multicentric study)

The interlaboratory validation of analytical procedures for the assay of urinary 3,5,6-trichloro-2-pyridinol (TCP) in the general Italian population is reported. The determinations were performed by high-resolution gas chromatography (HRGS) with electron capture detection and HRGS with mass spectrometry (MS) in 2 laboratories. The urine samples were from 42 participants from 3 regions of Italy. The results were evaluated by interlaboratory quality control. Urinary TCP concentrations were above the detection limit (1.2 micrograms/L) in 88% of the population, with a mean detectable concentration [GM (GSD)] of 2.8 (1.9) micrograms/g creatinine (creat). (GM, geometric mean; GSD, geometric standard deviation.) The Mann-Whitney U test showed that wine consumption was a statistically significant variable (p < 0.05) for urinary concentrations of TCP. Analysis of variance of the logarithm of urinary TCP versus wine consumption and diet showed a statistically significant fit. The model used explained 30% of the total variance: wine consumption and diet accounted for 37 and 17% respectively of the explained variance.     

Multicenter validation of PCR-based method for detection of Salmonella in chicken and pig samples

As part of a standardization project, an interlaboratory trial including 15 laboratories from 13 European countries was conducted to evaluate the performance of a noproprietary polymerase chain reaction (PCR)-based method for the detection of Salmonella on artificially contaminated chicken rinse and pig swab samples. The 3 levels were 1-10, 10-100, and 100-1000 colony-forming units (CFU)/100 mL. Sample preparations, including inoculation and pre-enrichment in buffered peptone water (BPW), were performed centrally in a German laboratory; the pre-PCR sample preparation (by a resin-based method) and PCR assay (gel electrophoresis detection) were performed by the receiving laboratories. Aliquots of BPW enrichment cultures were sent to the participants, who analyzed them using a thermal lysis procedure followed by a validated Salmonella-specific PCR assay. The results were reported as negative or positive. Outlier results caused, for example, by gross departures from the experimental protocol, were omitted from the analysis. For both the chicken rinse and the pig swab samples, the diagnostic sensitivity was 100%, with 100% accordance (repeatability) and concordance (reproducibility). The diagnostic specificity was 80.1% (with 85.7% accordance and 67.5% concordance) for chicken rinse, and 91.7% (with 100% accordance and 83.3% concordance) for pig swab. Thus, the interlaboratory variation due to personnel, reagents, thermal cyclers, etc., did not affect the performance of the method, which will be proposed as part of a developing international PCR standard.     

Analytical performance of the AtheNA MultiLyte® ANA II assay in sera from lupus patients with multiple positive ANAs

The purpose of this study was to evaluate the precision and accuracy of a commercial multiplexed kit for the measurement of 9 anti-nuclear antibodies (ANAs; anti-SS/A, anti-SS/B, anti-Sm, anti-RNP, anti-Jo-1, anti-Scl-70, anti-dsDNA, anti-Centromere B, and anti-Histone), and to compare these results to a subset of ANAs measured by enzyme-linked immunosorbent assays (ELISA) and immunodiffusion (ID). Sera were obtained from 22 systemic lupus erythematosus (SLE) patients, twelve controls and five others (commercial source) with various autoimmune diseases. ANA results from the AtheNA MultiLyte ANA II Assay (AtheNA) were compared to ELISA results (controls) and patients (ID). The AtheNA interassay coefficients of variation (CVs, N = 39, performed in duplicate; replicated 3x) ranged from 6.2% to 16.7% (mean = 9.8%), while the intra-assay CVs ranged from 5.8% to 14.3% (mean = 10.8%). Compared to results for SLE cases and controls, the sensitivity of AtheNA ranged from 85.7% to 100% (mean = 97.1%), while diagnostic specificity ranged from 16.7% to 100% (mean = 71.6%). There was significant agreement (P values ranging from 0.0001 to 0.03) when analytes coanalyzed by AtheNA and ELISA/ID were evaluated using Cohen's kappa (kappa values ranging from 0.376 to 1.000). No false positive ANA results were observed for either the control or commercial source autoimmune disease sera. These results indicate that the AtheNA assay is a precise and accurate alternative for performing multiple ELISAs or IDs in the diagnosis of autoimmune diseases, especially when the number of sera to be tested is large, such as in clinical screening or epidemiologic studies. It also appears that the AtheNA assay identifies positive ANA specificities which are missed by ID techniques, suggesting that it may have greater analytical sensitivity for some ANAs.     

Quantitative analysis of phylloquinone (vitamin K1) in soy bean oils by high-performance liquid chromatography

A high-performance liquid chromatographic method for determining phylloquinone (vitamin K1) in soy bean oils is described. Resolution of vitamin K1 from interfering peaks of the matrix was obtained after enzymatic digestion, extraction and liquid-solid chromatography on alumina. An isocratic reversed-phase chromatography with UV detection was used in the final stage. The quantitation was carried out by the standard addition method, and the recovery of the whole procedure was 88.2%.     

Determination of vitamin B12 in milk products and selected foods by optical biosensor protein-binding assay: method comparison

Biomolecular interaction analysis was evaluated for the automated determination of vitamin B12 in a range of foods. The analytical technique was configured as a biosensor-based, nonlabeled inhibition protein-binding assay using nonintrinsic R-protein. Sample extraction conditions were optimized, and both ligand specificity and nonspecific binding considerations were evaluated. Performance parameters included a quantitation range of 0.08-2.40 ng/mL, recoveries of 89-106%, agreement against assigned reference values for 3 independent certified food reference materials, and a mean between-laboratory reproducibility relative standard deviation of 4.9%. The proposed method was compared with reference microbiological and radioisotope protein-binding methods for a range of food samples. A wide selection of milks, infant formulas, meats, and liver were evaluated for their vitamin B12 content. The influence of season was studied in herd milk, early lactation was followed for a single animal, and the cobalamin content of bovine, caprine, and ovine milks was compared.     

Method development for the quantitation of ABT-578 in rabbit artery tissue by 96-well liquid-liquid extraction and liquid chromatography/tandem mass spectrometric detection

Quantitative determination of drug concentrations in tissue samples can provide critical information for drug metabolism, kinetics, and toxicity evaluations. For analysis of tissue samples using liquid chromatography/tandem mass spectrometric (LC/MS/MS) detection, homogenization is a critical step in achieving good assay performance. Assay performance can be closely evaluated by spiking the drug directly into tissue samples prior to homogenization. It is especially important to include this assay evaluation for the analysis of artery tissue samples because artery tissue is very elastic, making it quite a challenge to develop an effective procedure for homogenization. An LC/MS/MS assay in 96-well format using liquid-liquid extraction was developed for analyzing ABT-578 in rabbit artery samples. Tissue quality control samples were prepared by spiking ABT-578 stock solutions directly into the tissue before homogenization. The usage of the tissue control samples gives a thorough evaluation of the sample preparation process that includes both homogenization and sample extraction. A 20% blood in saline solution was used as a homogenization solution. Calibration standards were made by spiking ABT-578 into rabbit whole blood. Blood quality control samples were also prepared by spiking ABT-578 into rabbit whole blood. These blood QC samples were used to confirm the validity of the calibration curve. A lower limit of quantitation of 0.050 ng/mL was achieved. The linear dynamic range of blood standards was from 0.050-30.3 ng/mL with the correlation coefficient (r) ranging from 0.9969-0.9996. Overall %CV was between 1.3 and 7.0%, and analytical recovery was between 98.2 and 105.8% for blood QC samples. The %CVs for tissue QC samples were between 6.7 and 13.0%, and analytical recovery after correction was between 93.5 and 114.3%.     

Determination of vitamin K1 isomers in foods by liquid chromatography with C30 bonded-phase column

Vitamin K1 was determined in a variety of foods by using reversed-phase liquid chromatography with a C30 column followed by post-column reduction to the fluorescent hydroquinone derivatives. Lipids were removed by lipase digestion, followed by single extraction into hydrocarbon, and the protocol was extended to selected natural and processed foods. Biologically active trans- and inactive ci-vitamin K1 isomers were measured individually to evaluate the true nutritional status of the products. Method performance parameters confirmed the validity of the technique. The use of the triacontyl-bonded C30 phase for selective phylloquinone isomer measurement extends previously validated AOAC Method 999.15 for vitamin K1 in milk and infant formula to a wider range of foods important in the human diet. The cis-vitamin K1 isomer contributes up to about 15% of total phylloquinone in certain foods.     

Performance of electrolyte assays in the United Kingdom—reference target values

Wales External Quality Assessment Scheme (WEQAS) is one of the largest external quality assessment (EQA) providers in the United Kingdom, with over 600 participants. Over the last two and a half years, reference target values have been used for the electrolyte panel in the WEQAS General Chemistry scheme. Reference methods have a vital role in that they ensure the transfer of accuracy from definitive methods to routine methods. Validated reference methods, using flame emission/atomic absorption spectrometry were established for sodium, potassium, calcium, magnesium and lithium. These methods were validated by direct comparison with the definitive method via the use of primary reference material. Comparison against the all laboratory trimmed mean (ALTM) showed a small mixed systematic error for sodium and potassium, with a maximum bias from the reference value of 1% and 2%, respectively. Lithium and magnesium data showed predominant systematic constant errors of +0.03 and +0.02 mmol/l, respectively. For calcium, ALTM results showed a mixed systematic error with a cross over in the reference range (5% positive bias and constant error of –0.1 mmol/l). Over 40% of participants used the cresolpthalein complexone method, greatly influencing the ALTM value, (11% bias, constant error –0.26 mmol/l). Other methods such as the ion selective electrode (ISE) method were in closer agreement to the reference method (–4% bias, +0.05 mmol/l constant error). The study highlights the pitfalls of using the overall mean data as an accuracy target in EQA schemes.Presented at the 8th Conference on Quality in the Spotlight, 17–18 March 2003, Antwerp, Belgium     

Determination of Vitamins E,D3, and K1 in Plasma by Liquid Chromatography-Atmospheric Pressure Chemical Ionization-Mass Spectrometry Utilizing a Monolithic Column

This paper reports a rapid, simple, and sensitive method for determination of vitamin D3, vitamin E acetate, and vitamin K1 in plasma using atmospheric pressure chemical ionization –high performance liquid chromatography–mass spectrometry. Plasma samples were prepared using solid phase extraction. The separation of compounds was achieved using a C₁₈ monolithic column and a mobile phase composed of methanol and 0.1% formic acid in gradient elution mode at a flow rate of 1.0 mL min^?1. Analytes were ionized using atmospheric chemical ionization in positive mode. Mass spectra were recorded at m/z = 385.23, 473.47, and 451.41 for vitamin D3, vitamin E, and vitamin K1, respectively. Vitamin D2 was used as an internal standard and its mass spectra was recorded at 397.28 m/z. The method was validated using ICH guidelines. The system suitability responses were calculated for retention time, number of theoretical plates, capacity factor, resolution, and the selectivity factor. System validation was evaluated for precision, specificity, and linearity of all compounds. The limits of detection for vitamin D3, vitamin E, and vitamin K1 were determined to be 0.1, 1.36, and 0.052 ng mL^?1, respectively. The accuracy, evaluated as % of recovery, was in the range of 96.4 to 102.4% and precision determined as the coefficient of variation was between 1.24 and 3.6%. The validated method was applied to real plasma samples.     

Selective chemiluminescence method for monitoring of vitamin K homologues in rheumatoid arthritis patients

Vitamin K is a fat-soluble vitamin involved in blood coagulation and bone metabolism. The detection and monitoring of vitamin K homologues in rheumatoid arthritis (RA) patients is a challenging problem due to the smaller concentrations of vitamin K and the presence of several interfering medications. Therefore, this study aimed to develop a new highly sensitive and selective chemiluminescence (CL) method designated to quantify vitamin K homologues in plasma of RA patients including phylloquinone (PK, vitamin K₁), menaquinone-4 (MK-4, vitamin K₂) and menaquinone-7 (MK-7, vitamin K₂). The method was based on the unique photochemical properties of vitamin K homologues that were exploited for selective luminol CL reaction. The correlation coefficients of 0.998 or more were obtained in the concentration ranges of 0.1-100 ng mL⁻¹ vitamin K homologues. The detection limits were 0.03-0.1 ng mL⁻¹ in human plasma for vitamin K homologues. The developed HPLC-CL system was successfully applied for selective determination of vitamin K homologues in plasma of RA patients. The developed method may provide a useful tool for monitoring vitamin K homologues in different clinical studies such as RA, osteoporosis and hepatocellular carcinoma in which vitamin K is intervented.     

Determination of vitamin K in milk and infant formulas by liquid chromatography: collaborative study

A simple procedure for determination of vitamin K1 was developed for routine compliance monitoring of supplemented infant formula and measurement of endogenous levels in milk and milk powders. Samples are digested with lipase and extracted into hexane; and aliquot is evaporated, reconstituted in methanol, and analyzed by reversed-phase LC. Post-column zinc reduction of phylloquinone facilitates detection by fluorescence. The procedure was subjected to an AOAC collaborative study involving 8 materials, each in blind duplicate, across the range of 5-120 micrograms/100 g solids and including NIST 1846 reference material. Thirty-three laboratories returned valid data which were then statistically analyzed for outliers and precision parameters. Mean RSDR (%) was 6.53 (4.33-10.94), with a mean HORRAT value of 0.33 (0.23-0.43) and RSDr:RSDR ratio of 0.74. K1 isomers (cis and trans) were aggregated with conventional C18 columns, but may be selectively estimated with use of the C30 column.     

Phyllohydroquinone (Vitamin K1 H2) and Phylloquinone (Vitamin K1): Purification and Spectral Analysis

Abstract

Simple procedures for the preparation of pure phyllohydroquinone and phylloquinone are described. Phylloquinone is reduced by sodium dithionite and the reduced vitamin is purified by reverse phase high performance liquid chromatography. The essential spectral properties of the pure vitamins in ethanol and methanol are cited. The data provide a convenient spectral method for the accurate determination of the absolute concentrations of the oxidized and reduced vitamins and the rates of oxidation of the reduced vitamin. Pure, dry phyllohydroquinone may be safely stored at -70[ddot]C under nitrogen for a period of months. The stability of Phyllohydroquinone in methanol at 25.0 ± 0.1[ddot]C is also reported.     

Multielement trace determination in SiC powders: assessment of interlaboratory comparisons aimed at the validation and standardization of analytical procedures with direct solid sampling based on ETV ICP OES and DC arc OES

The members of the committee NMP 264 “Chemical analysis of non-oxidic raw and basic materials” of the German Standards Institute (DIN) have organized two interlaboratory comparisons for multielement determination of trace elements in silicon carbide (SiC) powders via direct solid sampling methods. One of the interlaboratory comparisons was based on the application of inductively coupled plasma optical emission spectrometry with electrothermal vaporization (ETV ICP OES), and the other on the application of optical emission spectrometry with direct current arc (DC arc OES). The interlaboratory comparisons were organized and performed in the framework of the development of two standards related to “the determination of mass fractions of metallic impurities in powders and grain sizes of ceramic raw and basic materials” by both methods. SiC powders were used as typical examples of this category of material. The aim of the interlaboratory comparisons was to determine the repeatability and reproducibility of both analytical methods to be standardized. This was an important contribution to the practical applicability of both draft standards. Eight laboratories participated in the interlaboratory comparison with ETV ICP OES and nine in the interlaboratory comparison with DC arc OES. Ten analytes were investigated by ETV ICP OES and eleven by DC arc OES. Six different SiC powders were used for the calibration. The mass fractions of their relevant trace elements were determined after wet chemical digestion. All participants followed the analytical requirements described in the draft standards. In the calculation process, three of the calibration materials were used successively as analytical samples. This was managed in the following manner: the material that had just been used as the analytical sample was excluded from the calibration, so the five other materials were used to establish the calibration plot. The results from the interlaboratory comparisons were summarized and used to determine the repeatability and the reproducibility (expressed as standard deviations) of both methods. The calculation was carried out according to the related standard. The results are specified and discussed in this paper, as are the optimized analytical conditions determined and used by the authors of this paper. For both methods, the repeatability relative standard deviations were <25%, usually ~10%, and the reproducibility relative standard deviations were <35%, usually ~15%. These results were regarded as satifactory for both methods intended for rapid analysis of materials for which decomposition is difficult and time-consuming. Also described are some results from an interlaboratory comparison used to certify one of the materials that had been previously used for validation in both interlaboratory comparisons. Thirty laboratories (from eight countries) participated in this interlaboratory comparison for certification. As examples, accepted results are shown from laboratories that used ETV ICP OES or DC arc OES and had performed calibrations by using solutions or oxides, respectively. The certified mass fractions of the certified reference materials were also compared with the mass fractions determined in the interlaboratory comparisons performed within the framework of method standardization. Good agreement was found for most of the analytes.     

United Nations Environment Programme Capacity Building Pilot Project--training and interlaboratory study on persistent organic pollutant analysis under the Stockholm Convention

Within the framework of a United Nations Environment Programme (UNEP) Capacity Building Project for training of laboratory staff in developing countries on persistent organic pollutant (POP) analysis, an interlaboratory study was organised following an initial evaluation of the performance of laboratories (reality check) and a series of training sessions. The target compounds were polychlorinated biphenyls (PCB) and organochlorine pesticides (OCP). Seven laboratories from five countries (Ecuador, Uruguay, Kenya, Moldova, and Fiji) participated. Most of the laboratories had no experience in determining PCBs. Although chromatograms improved considerably after the training and installation of new gas chromatographic (GC) columns at participating laboratories, the level of performance in the interlaboratory study was essentially on par with the moderate performance level achieved by European POP laboratories in the 1980s. Only some individual results were within +/-20% of the target values. The relative standard deviations (R.S.D.s) in POP concentrations determined by laboratories in a sediment sample were >200% in a number of cases. The results for a certified herring sample were better with at least some R.S.D. values below 50% and most below 100%. Clean up was as one of the main sources of error. After inspection it was ascertained that training of laboratory staff and investments in simple consumables such as glassware and GC columns would help to improve the quality of the analysis more than major investments in expensive instrumentation. Creating an effective network of POP laboratories at different continents together with a series of interlaboratory studies and workshops is suggested to improve the measurements of POPs in these countries.     

Determination of vitamin K homologues by high-performance liquid chromatography with on-line photoreactor and peroxyoxalate chemiluminescence detection

A sensitive and highly selective high-performance liquid chromatography (HPLC) method was developed for the determination of vitamin K homologues including phylloquinone (PK), menaquinone-4 (MK-4) and menaquinone-7 (MK-7) in human plasma using post-column peroxyoxalate chemiluminescence (PO-CL) detection following on-line ultraviolet (UV) irradiation. The method was based on ultraviolet irradiation (254 nm, 15 W) of vitamin K to produce hydrogen peroxide and a fluorescent product at the same time, which can be determined with PO-CL detection. The separation of vitamin K by HPLC was accomplished isocratically on an ODS column within 35 min. The method involves the use of 2-methyl-3-pentadecyl-1,4-naphthoquinone as an internal standard. The detection limits (signal-to-noise ratio = 3) were 32, 38 and 85 fmol for PK, MK-4 and MK-7, respectively. The recoveries of PK, MK-4 and MK-7 were greater than 82% and the inter- and intra-assay R.S.D. values were 1.9-5.4%. The sensitivity and selectivity of this method were sufficient for clinical and nutritional applications.     

Significant improvements in the analysis of perfluorinated compounds in water and fish: Results from an interlaboratory method evaluation study

The 2nd international interlaboratory study (ILS) on perfluorinated compounds (PFCs) in environmental samples was organized to assess the performance of 21 North American and European laboratories on the analysis of PFCs in water and fish. A study protocol was provided to assess accuracy, precision, matrix effects and to study the use of in-house standards. The participants used shared native and mass-labelled standards that were provided for this study to quantify the PFC concentrations in the samples. Matrix effects in the determination of PFCs can be considerable and can decrease the sensitivity, the accuracy and internal standard recoveries. Therefore, two quantification methods were evaluated by all laboratories: standard addition quantification (SAQ) and solvent-based calibration curve quantification (SBCCQ; using mass-labelled internal standards (IS)). The between laboratory reproducibility (i.e. coefficient of variance) was smaller for the SBCCQ results (except for PFBS and PFHxS for which no mass-labelled analogues were available) compared to those obtained by the SAQ method. The within laboratory precision of individual laboratories is good (mean for all PFCs in water 12% and 6.8% in fish). The good performance is partially attributable to the use of well-defined native- and mass-labelled standards. Therefore, the SBCCQ method is recommended. The results show that analytical methods for PFCs in water and fish have improved considerably. Critical steps identified in this study are (i) the use of well-defined native standards for quantification, (ii) the use of mass-labelled internal standards (preferably one for each target compound) and (iii) minimization of matrix effects by a better clean up.