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Organisationseinheit der BAM
The CCQM-K78.b key comparison was coordinated by the Bureau International des Poids et Mesures (BIPM) on behalf of the CCQM Organic Analysis Working Group (OAWG) of the 'Comité Consultatif pour la Quantité de Matière' (CCQM), for National Measurement Institutes (NMIs) and Designated Institutes (DIs) providing measurement services in organic analysis under the 'Comité International des Poids et Mesures' (CIPM) Mutual Recognition Arrangement (MRA).
This key comparison was conducted as a 'Track A' comparison within the OAWG's 10-year strategic plan. The goal of CCQM-K78.b was to underpin capabilities for the value assignment of calibration solutions containing low polarity/non-polar organic analytes in organic solvents. The selected model system consisted of a two-component pesticide solution in acetonitrile, comprising methoxychlor and trifluralin.
Participants were tasked with assigning the mass fractions, in units of μg/g, of methoxychlor and trifluralin in acetonitrile solution. The mass fraction levels and analytical challenges of the selected analytes were representative of those encountered for calibration solutions of non-polar organic analytes. Participation in CCQM-K78.b allowed for the benchmarking of capabilities for assigning the mass fraction of non-polar organic compounds (pKow < -2) in solution, at mass fractions above 5 μg/g, in an organic solvent. Additionally, the comparison assessed the capabilities for the quantitative assignment of thermally labile compounds.
Participants were provided by the BIPM with ampoules containing methoxychlor and trifluralin in acetonitrile. Each participant reported the mass fraction content of each analyte in μg/g. All participants ensured the metrological traceability of their results through the use of a Primary Reference Material (PRM), which was used to prepare a primary calibrator solution for each analyte using a gravimetric procedure. The twenty participating institutes primarily used analysis procedures based on GC-MS, -IDMS, -MS/MS, -ECD, and -FID, with some participants also using LC-UV for the value assignment.
The analysis of methoxychlor and trifluralin in acetonitrile solution presented several challenges, including the thermal stability of the analytes under selected analytical techniques, control of solvent volatility, and considerable variation in some results using MS-based quantification methods. The mass fraction assignments for methoxychlor and trifluralin, consistent with the key comparison reference values (KCRVs), were achieved with associated relative standard uncertainties of (0.38 - 2.9) % for methoxychlor and (0.35 - 2.5) % for trifluralin.
To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.
The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
The demonstration of competency and equivalence for the assessment of levels of contaminants and nutrients in primary foodstuffs is a priority within the 10-year strategy for the OAWG Track A core comparisons. The measurements are core challenges for reference material producers and providers of calibration Services. This key comparison related to low polarity analytes in a high fat, low protein, low carbohydrate food matrix and Benzo[a]pyrene in edible oil was the model System selected to align with this class within the OAWG strategy. Evidence of successful participation in formal, relevant international comparisons is needed to document measurement capability claims (CMCs) made by national metrology institutes (NMIs) and designated institutes (Dis). 16 National Metrology Institutions participated in the Track A Key Comparison CCQM-K146 Low-Polarity Analyte in high fat food: Benzo[a]pyrene in Olive Oil. Participants were requested to evaluate the mass fractions, expressed in µg/kg, of Benzo[a]pyrene in the olive oil material. The KCRV was determined from the results of all NMIs/DIs participating in the key comparison that used appropriately validated methods with demonstrated metrological traceability. Different methods such as liquid-liquid extraction, GPC and SPE were applied in the sample pretreatment and HPLC-FLD, HPLC-MS/MS, and GC-MS or GC-MS/MS were applied for detection by the participants. The mass fractions for BaP were in the range of (1.78 to 3.09) µg/kg with Standard uncertainties of (0.026 to 0.54) µg/kg, with corresponding relative Standard uncertainties from 0.9% to 21%. Five labs withdrew their result from the Statistical evaluation of the KCRV for technical reasons. One lab was excluded from the KCRV evaluation, as they did not meet the CIPM metrological traceability requirements. A Hierarchical Bayes option was selected for the KCRV value, which was determined as 2.74 µg/kg with a Standard uncertainty of 0.03 µg/kg. The 10 institutes those were included in the calculation of the consensus KCRV all agreed within their Standard uncertainties. Successful participation in CCQM-K146 demonstrates the measurement capabilities in determining mass fraction of organic compounds, with molecular mass of 100 g/mol to 500 g/mol, having low polarity pKow < -2, in mass fraction range from 0.1 µg/kg to 1000 µg/kg in a high fat, low protein, low carbohydrate food matrix.
Solutions of organic analytes of known mass fraction are typically used to calibrate the measurement processes used to determine these compounds in matrix samples. Appropriate value assignments and uncertainty calculations for calibration solutions are critical for accurate measurements. Evidence of successful participation in formal, relevant international comparisons is needed to document measurement capability claims (CMCs) made by national metrology institutes (NMIs) and designated institutes (DIs). To enable NMIs and DIs to update or establish their claims, in 2015 the Organic Analysis Working Group (OAWG) sponsored CCQM-K131 "Low-Polarity Analytes in a Multicomponent Organic Solution: Polycyclic Aromatic Hydrocarbons (PAHs) in Acetonitrile".
Polycyclic aromatic hydrocarbons (PAHs) result from combustion sources and are ubiquitous in environmental samples. The PAH congeners, benz[a]anthracene (BaA), benzo[a]pyrene (BaP), and naphthalene (Nap) were selected as the target analytes for CCQM-K131. These targets span the volatility range of PAHs found in environmental samples and include potentially problematic chromatographic separations. Nineteen NMIs participated in CCQM-K131. The consensus summary mass fractions for the three PAHs are in the range of (5 to 25) μg/g with relative standard deviations of (2.5 to 3.5) %.
Successful participation in CCQM-K131 demonstrates the following measurement capabilities in determining mass fraction of organic compounds of moderate to insignificant volatility, molar mass of 100 g/mol up to 500 g/mol, and polarity pKow < −2 in a multicomponent organic solution ranging in mass fraction from 100 ng/g to 100 μg/g: (1) value assignment of primary reference standards (if in-house purity assessment carried out), (2) value assignment of single and/or multi-component organic solutions, and (3) separation and quantification using gas chromatography or liquid chromatography.
