The feasibility of the production of a reference material for pesticide residue analysis in a cucumber matrix was investigated. Cucumber was spiked at 0.075 mg/kg with each of the 15 selected pesticides (acetamiprid, azoxystrobin, carbendazim, chlorpyrifos, cypermethrin, diazinon, (α + β)-endosulfan, fenitrothion, imazalil, imidacloprid, iprodione, malathion, methomyl, tebuconazole and thiabendazole) respectively. Three different strategies were considered for processing the material, based on the physicochemical properties of the vegetable and the target pesticides. As a result, a frozen spiked slurry of fresh cucumber, a spiked freeze-dried cucumber powder and a freeze-dried cucumber powder spiked by spraying the powder were studied. The effects of processing and aspects related to the reconstitution of the material were evaluated by monitoring the pesticide levels in the three materials. Two separate analytical methods based on LC–MS/MS and GC–MS/MS were developed and validated in-house. The spiked freeze-dried cucumber powder was selected as the most feasible material and more exhaustive studies on homogeneity and stability of the pesticide residues in the matrix were carried out. The results suggested that the between-unit homogeneity was satisfactory with a sample intake of dried material as low as 0.1 g. A 9-week isochronous stability study was undertaken at −20 °C, 4 °C and 18 °C, with −70 °C designated as the reference temperature. The pesticides tested exhibited adequate stability at −20 °C during the 9-week period as well as at −70 °C for a period of 18 months. These results constitute a good basis for the development of a new candidate reference material for selected pesticides in a cucumber matrix.Electronic supplementary materialThe online version of this article (doi:10.1007/s00216-015-8476-x) contains supplementary material, which is available to authorized users.

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The key comparison CCQM-K102: Polybrominated diphenyl ethers in sediment was coordinated by the JRC, Directorate F - Health, Consumers & Reference Materials, Geel (Belgium) under the auspices of the Organic Analysis Working Group (OAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM). Thirteen National Metrology institutes or Designated Institutes and the JRC participated. Participants were requested to report the mass fraction (on a dry mass basis) of BDE 47, 99 and 153 in the freshwater sediment study material. The sediment originated from a river in Belgium and contained PBDEs (and other pollutants) at levels commonly found in environmental samples. The comparison was designed to demonstrate participants' capability of analysing non-polar organic molecules in abiotic dried matrices (approximate range of molecular weights: 100 to 800 g/mol, polarity corresponding to pKow < −2, range of mass fraction: 1–1000 μg/kg). All participants (except one using ultrasonic extraction) applied Pressurised Liquid Extraction or Soxhlet, while the instrumental analysis was performed with GC-MS/MS, GC-MS or GC-HRMS. Isotope Dilution Mass Spectrometry approach was used for quantification (except in one case). The assigned Key Comparison Reference Values (KCRVs) were the medians of thirteen results for BDE 47 and eleven results for BDE 99 and 153, respectively. BDE 47 was assigned a KCRV of 15.60 μg/kg with a combined standard uncertainty of 0.41 μg/kg, BDE 99 was assigned a KCRV of 33.69 μg/kg with a combined standard uncertainty of 0.81 μg/kg and BDE 153 was assigned a KCRV of 6.28 μg/kg with a combined standard uncertainty of 0.28 μg/kg. The k-factor for the estimation of the expanded uncertainty of the KCRVs was chosen as k = 2. The degree of equivalence (with the KCRV) and its uncertainty were calculated for each result. Most of the participants to CCQM-K102 were able to demonstrate or confirm their capabilities in the analysis of non-polar organic molecules in abiotic dried matrices. Throughout the study it became clear that matrix interferences can influence the accurate quantification of the PBDEs, if the analytical methodology applied is not appropriately adapted and optimised. This comparison shows that quantification of PBDEs at the μg/kg low-middle range in a challenging environmental abiotic dried matrix can be achieved with relative expanded uncertainties below 15 % (more than 70 % of participating laboratories), well in line with the best measurement performances in the environmental analysis field. Main text 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 kcdb.bipm.org/. 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).

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The Joint Research Centre (JRC) of the European Commission has recently released two new Certified Reference Materials (CRMs) for the analysis of brominated flame retardants (BFRs): the freshwater sediment ERM-CC537a and the fish tissue ERM-CE102. The production of these CRMs responds to the need of expanding the offer of quality assurance/quality control tools for the analysis of BFRs in the fields of environmental analysis and food control, especially for compliance purposes. The sediment ERM-CC537a carries certified values for polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDD) diastereoisomers in the μg/kg range (dry mass), while the fish tissue ERM-CE102 is certified for PBDEs in the ng/kg range (wet weight). ERM-CC537a is the first reference material ever available with certified values for α-, β- and γ-HBCDD. The assignment of the certified values was performed via an intercomparison of expert laboratories. The evaluation of the data confirms the improving trend, observed in recent years, regarding the comparability of PBDE measurement results. The relative standard deviation (RSD) among laboratories is slightly better for the fish material (8–11%) compared to the sediment (9–15%), despite lower mass fractions in the biota matrix. The RSD of HBCDD data (17%) reveals that they are more challenging analytes. The average measurement uncertainty declared by the participants is about 30%, but an in-depth analysis of their performance reveals that it should be feasible to reduce the uncertainty budget.