The certification of the mass fraction of pesticides in cucumber : ERM-BC403 : certification report

This report describes the production of ERM®-BC403, which is a cucumber material certified for the mass fraction of selected pesticides. This material was produced following ISO Guide 34:2009 [1] and is certified in accordance with ISO Guide 35:2006 [2]. Cucumbers from a biodynamic farm were used as base material. The cucumbers were transformed into slurry, freeze-dried and cryogenically milled. The obtained product was partially reconstituted with water and a separate portion was spiked with a pesticide mixture. The contaminated portion was then mixed with the rest of the material, homogenised and accurately dispensed into 100-ml vials. A second freeze-drying cycle was applied with the vials placed directly in the freeze-dryer. Prior to analysis the resulting sponge of dry cucumber must be reconstituted with a specific volume of water. Between-unit homogeneity was quantified and stability during dispatch and storage were assessed in accordance with ISO Guide 35:2006 [2]. The material was characterised by an interlaboratory comparison of laboratories of demonstrated competence and adhering to ISO/IEC 17025 [3]. Technically invalid results were removed but no outliers were eliminated on statistical grounds only. Uncertainties of the certified values were calculated in accordance with the Guide to the Expression of Uncertainty in Measurement (GUM) [4] and include uncertainties related to possible inhomogeneity, instability and characterisation. The material is intended for the quality control / assessment of method performance. As with any reference material, it can be used for establishing control charts or used for validation of analytical methods. The CRM is available in sets of two glass vials containing each approximately 3.2 g of dried material. The vials were sealed under an atmosphere of argon. The minimum amount of sample to be used is 2.5 g of the reconstituted material.