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A rapid dialysis method for the analysis of stevioside SS and rebaudioside A RS in foods was developed. Minced samples 10 g were packed into 30 cm net length dialysis tubing with 30 methanol to increase the dialysis efficiency. The dialysis tubing was put in a 100 mL centrifuge tube, and the total fluid volume was made up to 100 mL with 30 methanol. Dialysis was done with shaking while heating at 50 . The dialysis times were reduced from 48-72 hr in the conventional method to 2 hr under these conditions. The dialysate was loaded on a C18 solid-phase extraction cartridge, and the cartridge was washed with 40 methanol. SS and RS were eluted from the cartridge with 80 methanol, and separated by reversed-phase HPLC. Recovery yields of SS and RS, spiked at 0.02 g/kg in various foods, were 83.0-105.1 and the relative standard deviations were mostly less than 5 .

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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.

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