1. Food (benzoic acid, sorbic acid) testing

3.3 Standard substance 3.3.1 Sodium benzoate (C. H, COONa, CAS No. 532-32-1), purity ≥ 99.0%; Or benzoic acid (C, HCOOH, CAS number 65-85-0), with a purity of ≥ 99.0%, or a national certified standard substance with sub standard substance certificates. 3.3.2 Potassium Sorbate (C.H, KO2, CAS No. 590-00-1). Purity ≥ 99.0%; Or sorbic acid (C.H.O.CAS number: 110-44-1), with a purity of ≥ 99.0%, or a standard substance certified by the country and issued with a certificate of reference substance i. 3.3 Saccharin sodium (C, H, CONNaSOz, CAS number: 128-44-9), with a purity of ≥ 99%, or a standard substance certified by the country and awarded with a certificate of reference substance. 3.4 Preparation of standard solution 3.4.1 Standard stock solution of benzoic acid, sorbic acid, and saccharin sodium (calculated as saccharin) (1000 mg/L): Accurately weigh 0.118 g, 0.134 g, and 0.117 g (accurate to 0.000 1 g) of sodium benzoate, potassium sorbate, and saccharin sodium, dissolve them in water and order them to 100 ml. Store at 4 ° C for a shelf life of 6 months. When using standards for benzoic acid and sorbic acid, it is necessary to dissolve them in methamphetamine and bring them to volume. Sodium saccharin contains crystalline water and needs to be dried at 120 ° C for 4 hours before use. Cool in a vacuum dryer to room temperature before use. 3.4.2 Mixed standard intermediate solution of benzoic acid, sorbic acid, and sodium saccharin (calculated as saccharin) (200mg/L): Accurately pipette 10.0 mL of each of the standard reserve solutions of benzoic acid, sorbic acid, and sodium saccharin into a 50 mL volumetric flask. Dilute to volume with water. Store at 4 ° C for a shelf life of 3 months. 3.4.3 Mixed standard series working solutions of benzoic acid, sorbic acid, and saccharin sodium (calculated by saccharin); Accurately aspirate 0 mL, 0.05 mL, 0.25 mL, 0.50 mL, 1.00 mL, 2.50 mL, 5.00 mL, and 10.0 mL of mixed standard intermediate solutions of benzoic acid, sorbic acid, and saccharin sodium, respectively, and dilute them to 10 mI. Prepare mixed standard series working solutions with mass concentrations of 0 mg/L. 1.00 mg/L. 5.00 mg/L. 10.0 mg/L. 20.0 mg/L. 50.0mg/L. 100mg/L and 200mg/L, respectively. Ready to use and ready to use. 3.5 Materials 3.5.1 Aqueous phase microporous filter membrane: 0.22 pm. 3.5.2 Plastic centrifuge tube: 50 mL. 4 Instruments and equipment 4.1 High performance liquid chromatography: equipped with ultraviolet detector 4.2 Analytical balance: sensitivity of 0.001 g and 0.000 1 go4.3 Vortex oscillator 4.4 Centrifuge: speed> 8000 r/min.4.5 homogenizer. 4.6 Thermostatic water bath pot. 4.7 Ultrasonic generator

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