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GB 5009.256-2025: National food safety standard - Determination of Phosphates in Foods Delivery: 9 seconds. True-PDF full-copy in English & invoice will be downloaded + auto-delivered via email. See step-by-step procedure Status: Valid GB 5009.256: Historical versions
Similar standardsGB 5009.256-2025: National food safety standard - Determination of Phosphates in Foods---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GB5009.256-2025GB NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA National Food Safety Standard - Determination of Phosphates in Foods Issued on: MARCH 16, 2025 Implemented on: SEPTEMBER 16, 2025 Issued by. National Health Commission of the People’s Republic of China; State Administration for Market Regulation. Table of ContentsForeword... 3 1 Scope... 4 Method I - Determination of 4 Phosphates in Foods... 4 2 Principle... 4 3 Reagents and Materials... 4 4 Instruments and Equipment... 6 5 Analytical Steps... 6 6 Expression of Analytical Results... 9 7 Precision... 10 8 Detection Limit and Quantitation Limit... 10 Method II - Determination of Total Content of Phosphate Radicals (PO43) in Foods 11 9 Principle... 11 10 Reagents and Materials... 11 11 Instruments and Equipment... 12 12 Analytical Steps... 13 13 Expression of Analytical Results... 14 14 Precision... 15 15 Detection Limit and Quantitation Limit... 15 Appendix A Ion Chromatogram of Standard Solutions of 4 Phosphates... 16 Appendix B Conversion Factors of Polyphosphate... 17 Appendix C Ion Chromatograms of Standard Solutions of Phosphates... 18 National Food Safety Standard - Determination of Phosphates in Foods1 ScopeThis Standard specifies the determination method for phosphates in foods in terms of phosphate radical (PO43). Method I of this Standard is applicable to the determination of phosphate, pyrophosphate, trimetaphosphate and tripolyphosphate in foods, but not to the determination of hexametaphosphate added in foods. Method II of this Standard is applicable to the determination of phosphates in foods in terms of phosphate radical (PO43). Method I - Determination of 4 Phosphates in Foods2 PrincipleAfter the specimen is extracted with sodium hydroxide solution and purified with solid phase extraction column, use potassium hydroxide solution to elute it, use anion exchange column to separate it, and use a conductivity detector for detection. The qualitative analysis is based on retention time and the quantitative analysis is based on the external standard method.3 Reagents and MaterialsUnless otherwise specified, all reagents used in this Method are guaranteed reagents and the water is Grade-1 water specified in GB/T 6682. 3.1 Reagents 3.1.1 Sodium hydroxide (NaOH). 3.1.2 Potassium hydroxide (KOH). 3.1.3 Methanol (CH3OH). chromatographically pure. 3.2 Preparation of Reagents 3.2.1 Sodium hydroxide solution (10 mmol/L). weigh-take 0.4 g of sodium hydroxide, add water to dissolve it and reach a constant volume of 1,000 mL. 3.2.2 Sodium hydroxide solution (50 mmol/L). weigh-take 2.0 g of sodium hydroxide, add water to dissolve it and reach a constant volume of 1,000 mL. 3.2.3 Potassium hydroxide solution (2 mol/L). weigh-take 112.0 g of potassium hydroxide, add water to dissolve it and reach a constant volume of 1,000 mL. 3.3 Standard Substances 3.3.1 Sodium phosphate (Na3PO4, CAS No.. 7601-54-9), purity 98%, or standard substance certified by the state and awarded with the standard substance certificate. 3.3.2 Sodium pyrophosphate (Na4P2O7, CAS No.. 7722-88-5), purity 98%, or standard substance certified by the state and awarded with the standard substance certificate. 3.3.3 Sodium trimetaphosphate [(NaPO3)3, CAS No.. 7785-84-4], purity 98%, or standard substance certified by the state and awarded with the standard substance certificate. 3.3.4 Sodium tripolyphosphate (Na5P3O10, CAS No.. 7758-29-4), purity 98%, or standard substance certified by the state and awarded with the standard substance certificate. 3.4 Preparation of Standard Solutions 3.4.1 Phosphate radical standard stock solution (1,000 mg/L). accurately weigh-take 0.173 g (accurate to 0.0001 g) of sodium phosphate standard substance, use 10 mmol/L sodium hydroxide solution to dissolve it and reach a constant volume of 100 mL. Per 1 L of this solution contains 1.0 g of phosphate radical. Store in a sealed container at room temperature, and it shall remain valid for 6 months. 3.4.2 Pyrophosphate standard stock solution (1,000 mg/L). accurately weigh-take 0.153 g (accurate to 0.0001 g) of sodium pyrophosphate, use 10 mmol/L sodium hydroxide solution to dissolve it and reach a constant volume of 100 mL. Per 1 L of this solution contains 1.0 g of pyrophosphate. Store in a sealed container at room temperature, and it shall remain valid for 6 months. 3.4.3 Trimetaphosphate standard stock solution (1,000 mg/L). dry the sodium trimetaphosphate in an oven at 103 C 2 C for 3 h. After cooling to room temperature in a desiccator, accurately weigh-take 0.132 g (accurate to 0.0001 g) of sodium trimetaphosphate standard substance, use 10 mmol/L sodium hydroxide solution to dissolve it and reach a constant volume of 100 mL. Per 1 L of this solution contains 1.0 g of trimetaphosphate. Store in a sealed container at room temperature, and it shall remain valid for 6 months. 3.4.4 Tripolyphosphate standard stock solution (1,000 mg/L). dry the sodium tripolyphosphate in an oven at 103 C 2 C for 3 h. After cooling to room temperature in a desiccator, accurately weigh-take 0.148 g (accurate to 0.0001 g) of sodium tripolyphosphate standard substance, use 10 mmol/L sodium hydroxide solution to dissolve it and reach a constant volume of 100 mL. Per 1 L of this solution contains 1.0 g of tripolyphosphate. Store in a sealed container at room temperature, and it shall remain valid for 6 months. 5.1.3 Milk powder, milk and dairy products, beverages, etc.. by repeatedly shaking and inverting the container, thoroughly mix the sample, until the sample is homogenized. 5.1.4 Solid grease, fats, cocoa products, chocolate and chocolate products, frozen drinks, etc.. take 500 g of sample, freeze it at -18 C, use a food pulverizer to pulverize it and evenly mix it for later use. 5.1.5 Cereals, wheat flour and its products, jelly, candy, syrup, canned vegetables, baked food, puffed food, cooked nuts and seeds, etc.. take 500 g of the edible part and use a food pulverizer to pulverize it for later use. 5.1.6 Seasonings, etc.. for powdery seasonings, repeatedly shake and invert the container to thoroughly mix the sample; for solid large granular seasonings, take 500 g and use a food pulverizer to pulverize it for later use. 5.1.7 Cereal and starch desserts, rice flour, infant formula and complementary food, etc.. repeatedly shake and invert the container to thoroughly mix the sample, until the sample is homogenized. 5.2 Sample Pre-treatment 5.2.1 Sample extraction 5.2.1.1 Vegetables, fruits, jelly, chocolate and candy, coarse cereals, wheat flour and its products, milk powder, milk and dairy products, beverages, etc.. weigh-take 2.5 g (accurate to 0.001 g, the sampling amount of the specimen can be appropriately adjusted) of the specimen, use 50 mmol/L sodium hydroxide solution to wash it into a 50 mL colorimetric tube, evenly mix it and reach a constant volume to the scale; extract it at 80 C for 30 min with ultrasound, and every 5 min, shake it once to make the sample completely dispersed. After cooling to room temperature, use filter paper to filter the solution; take the filtrate, and at 4 C, centrifuge it at 8,000 r/min for 10 min, and take the supernatant for later use. 5.2.1.2 Puffed food, cooked nuts and seeds, cereals and starch desserts, rice flour, infant formula and complementary food, etc.. weigh-take 2.5 g (accurate to 0.001 g, the sampling amount of the specimen can be appropriately adjusted) of the specimen, and use 50 mmol/L sodium hydroxide solution to wash it into a 25 mL colorimetric tube, evenly mix it and reach a constant volume to the scale; extract it at 80 C for 30 min with ultrasound, and every 5 min, shake it once to make the sample completely dispersed. After cooling to room temperature, use filter paper to filter the solution; take the filtrate, and at 4 C, centrifuge it at 8,000 r/min for 10 min, and take the supernatant for later use. 5.2.1.3 Grease, fats, seasonings, etc.. weigh-take 1 g (accurate to 0.001g, the sampling amount of the specimen can be appropriately adjusted) of the specimen, use 50 mmol/L sodium hydroxide solution to wash it into a 50 mL colorimetric tube, evenly mix it and reach a constant volume to the scale; extract it at 80 C for 30 min with ultrasound, and every 5 min, shake it once to make the sample completely dispersed. After cooling to room temperature, use filter paper to filter the solution; take the filtrate, and at 4 C, centrifuge it at 8,000 r/min for 10 min, and take the supernatant for later use. 5.2.1.4 Aquatic products, eggs, meat and their products. weigh-take 2.5 g (accurate to 0.001 g, the sampling amount of the specimen can be appropriately adjusted) of the specimen, use 50 mmol/L sodium hydroxide solution to wash it into a 100 mL colorimetric tube, evenly mix it and reach a constant volume to the scale; extract it at 80 C for 30 min with ultrasound, and every 5 min, shake it once to make the sample completely dispersed. After cooling to room temperature, use filter paper to filter the solution; take the filtrate, and at 4 C, centrifuge it at 8,000 r/min for 10 min, and take the supernatant for later use. 5.2.2 Sample purification Take 15 mL of the supernatant after the treatment in 5.2.1, pass it through a 0.45 m water- soluble membrane syringe filter and a polydivinylbenzene polymer reverse phase packed column, discard the first 3 mL (if the chloride ion is greater than 100 mg/L, then, it needs to successively pass through a syringe filter, a polydivinylbenzene polymer reverse phase packed column, an Ag column and a Na column, and discard the first 7 mL), and collect the remaining eluate for testing. Before determination, the solution to be tested shall be appropriately diluted in accordance with the sample content. Before use, the solid phase extraction column needs to be activated. For example, when using a polydivinylbenzene polymer reverse phase packed column (1.0 mL), an Ag column (1.0 mL), or a Na column (1.0 mL), the activation process is as follows. before use, the polydivinylbenzene polymer reverse phase packed column (1.0 mL) is successively passed with 10 mL of methanol and 15 mL of water and left to stand for activation for 30 min. The Ag column (1.0 mL) and the Na column (1.0 mL) are passed with 10 mL of water and left to stand for activation for 30 min. 5.3 Reference Chromatographic Conditions 5.3.1 Chromatographic columns. anion exchange column (4 mm 250 mm); guard column. anion exchange column (4 mm 50 mm) with the same filler, or an ion chromatography column with equivalent performance. 5.3.2 Eluent. potassium hydroxide solution. The gradient elution time and potassium hydroxide concentration are shown in Table 1.The flow rate is 1.0 mL/min. 5.3.3 Suppressor. anion suppressor or equivalent suppression device. 5.3.4 Detector. conductivity detector, detection cell temperature is 35 C. 5.3.5 Column oven. the temperature of the column oven is 30 C. 5.3.6 Injection volume. 100 L. ρi---the determined value of the ith phosphate radical in the sample solution, expressed in (mg/L); ρ0i---the determined value of the ith phosphate radical in the sample blank solution, expressed in (mg/L); V---the constant volume of the sample extracting solution, expressed in (mL); m---the weighed mass of the sample, expressed in (g); 1,000---the conversion factor. The calculation result is expressed as the arithmetic mean of two independent determination results obtained under repeatability conditions, and the result shall retain three significant figures. If the analytical result needs to be expressed in terms of phosphate radical content, see Appendix B, and multiply the polyphosphate content by the conversion factor F. The total phosphate radical in the sample is the sum of phosphate radicals converted from polyphosphates (except hexametaphosphate).7 PrecisionThe absolute difference between two independent determination results obtained under repeatability conditions shall not exceed 15% of the arithmetic mean.8 Detection Limit and Quantitation LimitPuffed food, cooked nuts and seeds, cereals and starch desserts, rice flour, infant formula and complementary food, etc.. take a sample of 2.5 g, reach a constant volume of 50 mL, and before determination, dilute 2.5 times. The detection limit of each polyphosphate determined is 0.002 g/kg, and the quantification limit is 0.005 g/kg. Vegetables, fruits, jelly, chocolates and candies, coarse cereals, wheat flour and its products, milk powder, milk and dairy products, beverages, etc.. take a sample of 2.5 g, reach a constant volume of 50 mL, and before determination, dilute 5 times. The detection limit of each polyphosphate determined is 0.003 g/kg, and the quantification limit is 0.01 g/kg. Grease, fats, seasonings, etc.. take a sample of 1.0 g and reach a constant volume of 50 mL; aquatic products, eggs, meat and their products. take a sample of 2.5 g and reach a constant volume of 100 mL, and before determination, dilute 2.5 times. The detection limit of each polyphosphate determined is 0.006 g/kg, and the quantification limit is 0.02 g/kg. Method II - Determination of Total Content of Phosphate Radicals (PO43) in Foods9 PrincipleAfter extraction, the phosphates in the specimen are converted into phosphate radical (PO43) ions under acidic conditions, separated by an anion exchange column and detected by a conductivity detector. The qualitative analysis is based on retention time and the quantitative analysis is based on the external standard method.10 Reagents and MaterialsUnless otherwise specified, all reagents used in this Method are guaranteed reagents, and the water is Grade-1 water specified in GB/T 6682. 10.1 Reagents 10.1.1 Nitric acid (HNO3). mass concentration is 65%. 10.1.2 Sodium carbonate (Na2CO3). 10.1.3 Sodium hydroxide (NaOH). 10.1.4 Potassium hydroxide (KOH). 10.2 Preparation of Reagents 10.2.1 Nitric acid solution (volume fraction 30%). measure-take 30 mL of nitric acid and slowly add it into 50 mL of water. After cooling to room temperature, dilute it to 100 mL. 10.2.2 Sodium hydroxide solution (50 mmol/L). same as 3.2.2. 10.2.3 Potassium hydroxide solution (2 mol/L). same as 3.2.3. 10.2.4 Sodium carbonate (15 mmol/L)-sodium hydroxide (2 mmol/L) mixed solution. respectively weigh-take 1.590 g of sodium carbonate and 0.080 g of sodium hydroxide, dissolve them in a beaker, cool to room temperature, then, transfer to a volumetric flask, and reach a constant volume of 1,000 mL. 10.3 Standard Substance Sodium phosphate (Na3PO4, CAS No.. 7601-54-9), purity 98%, or standard substance certified by the state and awarded with the standard substance certificate. 10.4 Preparation of Standard Solutions12 Analytical Steps12.1 Preparation of Specimens Same as 5.1. 12.2 Sample Pre-treatment Weigh-take 1 g ~ 2 g of sample (the sample amount can be appropriately adjusted according to the actual situation, accurate to 0.001 g) into a 50mL colorimetric tube (10.5.2), add 45 mL of 50 mmol/L sodium hydroxide solution, evenly mix it by vortex for 1 min, and extract it at 80 C for 30 min with ultrasound. Every 5 min, shake it once to keep the solid phase completely dispersed. After cooling to room temperature, use water to reach a constant volume of 50 mL. After shaking, transfer it all to a 50 mL centrifuge tube and centrifuge it at 8,000 r/min for 5 min. Measure-take 5.00 mL of the extracting solution into another 50 mL colorimetric tube (10.5.2), add 1 mL of 30% nitric acid (10.2.1), evenly mix it by vortex, place in a 90 C 5 C water bath to heat for 60 min. Take out and place in cold water to cool to room temperature, add water to reach a constant volume to the scale and shake it well. Transfer 2.00 mL of the solution into a 10 mL centrifuge tube, use water to dilute to the scale, place the solution in a refrigerated centrifuge, and centrifuge at 4 C and 8,000 r/min for 5 min. Take the supernatant and filter it through a 0.45 m filter membrane; take an appropriate amount for on-machine testing. 12.3 Reference Chromatographic Conditions 12.3.1 Potassium hydroxide eluent system 12.3.1.1 Chromatographic columns. hydroxide selective, anion exchange column (250 mm 4 mm), guard column. anion exchange column (50 mm 4 mm) with the same filler, or an ion chromatography column with equivalent performance. 12.3.1.2 Eluent. potassium hydroxide eluent, concentration is 20 mmol/L, flow rate is 1.0 mL/min. 12.3.1.3 Suppressor. anion suppressor. 12.3.2 Carbonate eluent system 12.3.2.1 Chromatographic column. carbonate selective, anion exchange column (4 mm 150 mm), guard column. anion exchange column (1 mm 3.5 mm) with the same filler, or an ion chromatography column with equivalent performance. 12.3.2.2 Eluent. sodium carbonate (15 mmol/L) + sodium hydroxide (2 mmol/L) mixed eluent, flow rate is 0.6 mL/min. 12.3.2.3 Suppressor. anion suppressor. ......Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al. 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