Use of Dialysis and Liquid-Liquid Extraction for the Determination of Propionic Acid by Gas Chromatography

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.