A simple and efficient method for the determination of propionic acid (PA) in foods was developed. The sample was cleaned up by dialysis, and PA in the resulting solution was extracted into ethyl acetate for GC analysis. Sodium sulfate was used as a salting-out agent in the extraction process, and GC-FID and GC-MS were successfully applied to the determination and confirmation of PA, respectively. The recoveries were in the range of 98.9–104.4% at the addition level of 0.2 g/kg from 6 foods, bread, cake, cheese, worcester sauce, vinegar-pickles and yogurt. To evaluate the performance of the developed method, recoveries from bread, cake and cheese were compared with those of the notified method at the maximal allowable addition level of PA as a preservative for each food. Recoveries of 98.2–99.5% for the developed method and 91.2–92.0% for the notified method were obtained. The analytical limit was 0.1 g/kg in samples for both determination and confirmation.
A GC-MS/MS method for determination of the rodenticide tetramethylenedisulfotetramine was developed. Tetramethylenedisulfotetramine was extracted from the sample with ethyl acetate in the presence of anhydrous sodium sulfate. Then, an aliquot of the extract was evaporated under vacuum, followed by acetonitrile/hexane partitioning, and cleanup with a tandem graphitized carbon/primary secondary amine (PSA) column, prior to GC-MS/MS analysis. The recoveries from 10 processed foods, all of which were fortified at 0.1 mg/kg, were in the range of 85–96%, and the relative standard deviations were less than 7%. The proposed method effectively removed co-extracted matrix components, and matrix effects were negligible in the GC-MS/MS analysis. In addition, no interfering peaks were found in the chromatograms of the blank samples at the retention time of tetramethylenedisulfotetramine, indicating that the method is highly selective. Overall results suggest that the proposed method is suitable for determining tetramethylenedisulfotetramine contained in processed foods.
In Japan, a regulatory limit of 0.5 μg/kg was set in 2015 for aflatoxin M1 (AFM1) in milk. A method using an immunochromatographic kit has been adopted as the official screening method, and criteria for the kit have been set. In order to confirm whether commercial immunochromatographic kits for detecting AFM1 satisfy these criteria, the performance of four kits was evaluated by performing spike-and-recovery experiments using AFM1-free milk samples and milk samples spiked at seven levels (100–700 ng/kg). With the two qualitative kits, determinations of blank samples were all negative and those of the samples spiked at 500 ng/kg were all positive. With the two quantitative kits, the measured values of the blank samples were all less than 100 ng/kg and the recoveries of the samples spiked at 500 ng/kg were all more than 70%. The detection limits of the two quantitative kits were both less than 100 ng/kg. These results indicate that all four immunochromatographic kits meet the criteria and can be used to screen AFM1 in milk.