GB5009.34—2016 Method for determination of sulfur dioxide in foods
GB5009.34—2016 Determination of sulfur dioxide in foods Sulphur dioxide rapid tester in food Model: KSO2-GB (GB5009.34 standard distillation method instrument) Product introduction: The sample is quickly distilled for 2-5 minutes, and it has safety protection function, high cost performance, saving time and effort. national standards of People's Republic of China GB5009.34—2016 National food safety standards 2016-08-31 released 2017-03-01 implementation People's Republic National Health and Family Planning Commission released GB5009.34—2016 Foreword This standard replaces GB/T5009.34—2003 “Determination of sulfites in foodâ€. Compared with GB/T5009.34-2003, this standard is mainly revised as follows: ———The standard name was changed to “Determination of Sulfur Dioxide in Foods National Food Safety Standardsâ€; --- Delete the first method and Appendix A; --- The original second method of distillation was changed to titration. GB5009.34—2016 1 National food safety standards Determination of sulfur dioxide in food 1 Scope This standard specifies the method for determination of total sulfur dioxide in foods such as preserved fruits, dried vegetables, rice flour, vermicelli, sugar, edible fungi and wine. This standard applies to the determination of total sulfur dioxide in foods such as preserved fruits, dried vegetables, rice flour, vermicelli, sugar, edible fungi and wine. 2 Principle The sample was acidified and distilled in a closed vessel, and the distillate was absorbed with a lead acetate solution. The absorbed solution is acidified with hydrochloric acid, and the iodine standard Quasi-solution titration, the sulfur dioxide content in the sample is calculated according to the amount of iodine standard solution consumed. 3 reagents and materials Unless otherwise stated, the reagents used in this method are of analytical grade and the water is the third grade water specified in GB/T6682. 3.1 Reagents 3.1.1 Hydrochloric acid (HCl). 3.1.2 Sulfuric acid (H2SO4). 3.1.3 Soluble starch [(C6H10O5)n]. 3.1.4 Sodium hydroxide (NaOH). 3.1.5 Sodium carbonate (Na2CO3). 3.1.6 Lead acetate (C4H6O4Pb). 3.1.7 Sodium thiosulfate (Na2S2O3·5H2O) or anhydrous sodium thiosulfate (Na2S2O3). 3.1.8 Iodine (I2). 3.1.9 Potassium iodide (KI). 3.2 reagent preparation 3.2.1 Hydrochloric acid solution (1+1): Measure 50 mL of hydrochloric acid, slowly pour into 50 mL of water, and stir while stirring. 3.2.2 Sulfuric acid solution (1+9): Measure 10 mL of sulfuric acid, slowly pour into 90 mL of water, and stir while stirring. 3.2.3 Starch indicator solution (10g/L): Weigh 1g of soluble starch, make a paste with a little water, slowly pour into 100mL boiling water, add Stir, boil for 2min, let cool for use, ready to use. 3.2.4 Lead acetate solution (20g/L): Weigh 2g of lead acetate, dissolve it in a small amount of water and dilute to 100mL. 3.3 Standards Potassium dichromate (K2Cr2O7), excellent grade purity, purity ≥99%. 3.4 standard solution preparation 3.4.1 Sodium thiosulfate standard solution (0.1mol/L): Weigh 25g of sodium thiosulfate containing water of crystallization or 16g of anhydrous sodium thiosulfate GB5009.34—2016 2 In 1000 mL of freshly boiled cold water, add 0.4 g of sodium hydroxide or 0.2 g of sodium carbonate, shake well, store in a brown bottle, place for two weeks, filter, and calibrate the exact concentration with potassium dichromate standard solution. Or purchase a certified sodium thiosulfate standard solution. 3.4.2 Iodine standard solution [c (1/2I2)=0.10mol/L]: Weigh 13g of iodine and 35g of potassium iodide, add about 100mL of water, add 3 drops of hydrochloric acid after dissolution, dilute to 1000mL with water, filter and transfer to brown bottle . Calibration with sodium thiosulfate standard solution before use. 3.4.3 Potassium dichromate standard solution [c (1/6K2Cr2O7)=0.1000mol/L]: accurately weigh 4.903g of potassium dichromate which has been dried to constant weight in an electric oven at 120 °C ± 2 °C, dissolved in The water was transferred to a 1000 mL volumetric flask and brought to volume. Or purchase a certified potassium dichromate standard solution. 3.4.4 Iodine standard solution [c (1/2I2) = 0.01000 mol/L]: The 0.1000 mol/L iodine standard solution was diluted 10 times with water. 4 Instruments and equipment 4.1 Full glass distiller: 500 mL, or equivalent distillation equipment. 4.2 Acid burette: 25mL or 50mL. 4.3 Shear mill. 4.4 Iodometric flask: 500mL. 5 Analysis steps 5.1 Sample preparation Fruits, dried vegetables, rice noodles, vermicelli and edible fungi are appropriately cut into small pieces, then cut with a shearing mill, stirred evenly, and set aside. 5.2 Sample distillation Weigh 5g of uniform sample (accurate to 0.001g, depending on the amount of sample), the liquid sample can directly draw 5.00mL ~ 10.00mL sample, placed in the distillation flask. Add 250 mL of water, install a condensing device, insert the lower end of the condensing tube into the surface of the iodine measuring flask pre-prepared with 25 mL of lead acetate absorbing solution, then add 10 mL of hydrochloric acid solution to the retort, immediately cover it, and heat and distill. When the distillate was about 200 mL, the lower end of the condenser was removed from the liquid surface and distilled for another 1 min. Rinse the portion of the device inserted with the lead acetate solution with a small amount of distilled water. At the same time, do a blank test. 5.3 Titration 10 mL of hydrochloric acid and 1 mL of starch indicating solution were sequentially added to the removed iodine measuring flask, and the mixture was shaken with an iodine standard solution until the color of the solution became blue and did not fade within 30 s, and the volume of the iodine standard titration solution consumed was recorded. 6 Expression of analysis results The content of sulfur dioxide in the sample is calculated according to formula (1): X = (V -V0) × 0.032 × c × 1000 m ..............................(1) In the formula: X ———The total content of sulfur dioxide (in terms of SO 2 ) in the sample, in grams per kilogram (g / kg) or grams per liter (g / L); V ——— volume of iodine standard solution used for titrating the sample, in milliliters (mL); V0 ———The volume of iodine standard solution used in the blank test, in milliliters (mL); 0.032———1mL iodine standard solution [c (1/2I2)=1.0mol/L] is equivalent to the mass of sulfur dioxide, the unit is gram (g); c ———Iodine standard solution concentration in moles per liter (mol/L); GB5009.34—2016 3 m ———The mass or volume of the sample in grams (g) or milliliters (mL). The calculated results are expressed as the arithmetic mean of two independent determinations obtained under repetitive conditions. When the sulfur dioxide content is ≥1 g/kg (L), the results retain three significant figures; when the sulfur dioxide content is <1 g/kg (L) The result retains two significant digits. 7 precision The absolute difference between two independent test results obtained under repeatability conditions shall not exceed 10% of the arithmetic mean. 8 other When taking 5g solid sample, the detection limit (LOD) of the method is 3.0mg/kg, the limit of quantification is 10.0mg/kg; when taking 10mL liquid sample, the detection limit (LOD) of the method is 1.5mg/L. The limit of quantification is 5.0 mg/L. 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