Recommendations analytical methods for food additives

chromatograph. Start temperature program when solvent peak emerges. Measure peak heights and calculate peak height ratios of benzoic acidphenylacetic acid. Use average of duplicate ratios. Peak height ratios for duplicate injections should differ ≤5 . Preparation of standard curves Transfer 1.00 mL standard solutions to five 8 mL test tubes with Teflon-lined screw caps. Add 0.20 mL silylating agent to each tube, cap, and let stand 15 min in oven or H 2 O bath at 60 ºC. Inject duplicate 1 µL portions of standard solutions into gas chromatograph. Use same conditions as for test portion solution. Measure peak heights and calculate peak height ratios of benzoic acidphenylacetic acid. Peak height ratios for duplicate injections should differ ≤5 . Plot weight ratios x versus average peak height ratios y for each preservative. Calculate slope and intercept of standard curve by method of least squares. Calculation y – a W ′ Preservative, mgkg ––––– × –– × 1000 [7.1] b W where: b = slope of standard curve a = intercept y = average peak height ratio of preservativeinternal standard W = weight of test portion in g W ′ = weight of internal standard in mg. AOAC liquid chromatographic method for benzoic acid in orange juice 8 Preparation of test samples for HPLC Place 10.0 mL orange juice sample into 50 mL centrifuge tube and centrifuge 5 min at 1500 g. Using 10 mL syringe, precondition C18 cartridge by passing 2 mL methanol through cartridge, followed by 5 mL H 2 O. Pipette 1.0 mL portion of test sample supernate into syringe and through conditioned cartridge. Slowly wash cartridge let eluate drip by slowly pushing plunger with 3.0 mL 2 acetonitrile in hexane and discard eluate. Push syringe plunger 3x, blowing air through cartridge to eliminate excess hexane in cartridge. Add 3.0 mL methanol to syringe. Slowly elute cartridge with 3 mL methanol and collect eluate in 5 mL graduated centrifuge tube. Adjust eluate final volume to 3.0 mL with methanol. Pass eluate through 0.45 µm filter into vial. Recovery test Determine recovery of benzoic acid in juices by dividing spiked juice sample into 2 equal portions. Filter 1 portion through 0.45 µm filter, as control sample, while passing other portion through C18 cartridge and 0.45 µm filter. Calculate recoveries