Report of the first interlaboratory comparison : plasticisers in gasket and oil

The Institute for Health and Consumer Protection (IHCP) of the European Commission's Directorate- General Joint Research Centre hosts the Community Reference Laboratory for Food Contact Materials (CRL-FCM). One of its core tasks is to organize interlaboratory comparisons (ILCs) among appointed National Reference Laboratories (NRLs). This report presents the results of the first ILC of the CRLFCM which focused on the determination of Plasticisers content in PVC Gasket and in Oil matrix. The test materials used in this exercise were virgin gasket lids coming from industrial sources for the proficiency exercise part A. For the second part of the exercise an industrial source of sunflower oil was used and spiked with several plasticisers by the CRL-FCM. There were 41 participants to whom samples were dispatched 34 of which submitted results for at least 1 analyte-material. 21 laboratories reported results for more than 10 analyte-material combination out of 14 required. The homogeneity studies were performed by the CRL-FCM laboratory. The assigned value and its uncertainty for part A, virgin gaskets, were obtained after applying the robust statistics to the results obtained from the participants. The assigned values for part B, oil samples, were those obtained based on formulation, from the gravimetric measurements used to spike the material. The uncertainty of the assigned values for oil samples was calculated combining the uncertainty of the spiking procedure with a contribution for the between-bottle homogeneity. Participants were invited to report four replicates measurements. This was done by most of the participants. Laboratory results were rated with z and z' scores in accordance with ISO 13528 [1] Standard deviations for proficiency assessment (also called target standard deviations) were set based on Horwitz equation for substances in the two oil samples. For the plasticisers in the two gasket samples the target standard deviation was set by the organizers to 15% in order to fulfil the required criteria for sufficient homogeneity of the sample within the lots.