Proficiency test on the determination of mineral oil in sunflower oil

Following the discovery of mineral oil contamination of Ukrainian sunflower oil in April 2008, the Institute for Reference Materials and Measurements (IRMM) of the European Commission's joint Research Centre (IRC) was requested by the Directorate General Health and Consumers (DG SANCO) to organise a proficiency test on the determination of mineral oil in sunflower oil. The aim or this test was to evaluate the comparability of analysis results gained by laboratories in the EU and the Ukraine. The organisation of the study and the evaluation of the results were done in accordance with "The International Harmonised Protocol for the Proficiency "'resting of Analytical Chemistry Laboratories" and ISO Guide 43. Altogether 62 laboratories from 19 EU member states, Switzerland and the Ukraine subscribed for participation in the study. Four test samples at concentration levels between about 100 and 350 mg/kg, comprising contaminated crude sunflower oil, contaminated refined sunflower oil, and spiked sunflower oil, and a solution of mineral oil in n-heptane were dispatched to the participants. The participants were asked to determine the mineral oil content of the test samples by application or their in-house analysis methods. In total, 55 sets or results were reported to the organisers of the study. The performance of laboratories was expressed by v.-scores for the oil samples and by relative bias for the mineral oil solution in n-heptane. The percentage of successful laboratories in the determination of the mineral oil content of sunflower oil was for all sunflower oil test materials about 80%.