An interlaboratory study was performed to evaluate the equivalence between an official method and a modified method of evaporation residue test using three food-simulating solvents (water, 4% acetic acid and 20% ethanol), based on the Japanese Food Sanitation Law for food contact products. Twenty-three laboratories participated, and tested the evaporation residues of nine test solutions as blind duplicates. For evaporation, a water bath was used in the official method, and a hot plate in the modified method. In most laboratories, the test solutions were heated until just prior to evaporation to dryness, and then allowed to dry under residual heat. Statistical analysis revealed that there was no significant difference between the two methods, regardless of the heating equipment used. Accordingly, the modified method provides performance equal to the official method, and is available as an alternative method.
Keywords: evaporation residue; food contact product; interlaboratory study; migration test; performance evaluation.