GB 1886.325-2021National food safety standard - Food additives - Potassium polymetaphosphate (English PDF)

2.1 Molecular formula

(KPO3)n

2.2 Relative molecular mass

118.069n (according to the international relative atomic mass in 2018)

3.1 Sensory requirements

Sensory requirements shall be in accordance with Table 1.

3.2 Physical and chemical indicators

Physical and chemical indicators shall be in accordance with Table 2.

A.1 General Provisions

The reagents and water that are used in this Standard, when no other requirements are specified, refer to analytical reagents and grade-III water which is specified in GB/T 6682. The standard solution, the standard solutions, preparations and products for impurity determination, which are used in the test, are all prepared in accordance with the provisions of GB/T 601, GB/T 602, and GB/T 603, when no other requirements are specified. The solution used in the test, if not indicated which solvent is used, refers to aqueous solution.

A.2 Identification test

A.2.1 Reagents and materials

A.2.1.1 Hydrochloric acid.

A.2.1.2 Silver nitrate solution: 17 g/L.

A.2.1.3 Ammonia solution: 2+3.

A.2.1.4 Nitric acid solution: 1+9.

A.2.1.5 Sodium acetate solution: 40 g/L.

A.2.2 Identification method

A.2.2.1 Identification of potassium ions

Weigh 0.1 g of the sample and dissolve it in 10 mL of water. Dip the platinum wire in hydrochloric acid; burn it on the flame until it is colorless; then, dip the sample solution and burn it on the flame; observe that the flame is purple under the cobalt glass.

A.2.2.2 Identification of phosphate

Weigh 1 g of the sample; dissolve it in 20 mL of water; add silver nitrate solution, to produce a yellow precipitate. This precipitate is soluble in ammonia solution or nitric acid solution.

A.3.5 Result calculation

Calculate the mass fraction w1 of phosphorus pentoxide (P2O5) (on a dry basis) according to Formula (A.1).

Where: m1 - the mass of quinoline phosphomolybdate precipitate that is formed by the test solution, in grams (g); m2 - the mass of quinoline phosphomolybdate precipitate that is formed by the blank solution, in grams (g);

0.032 07 - the coefficient of conversion of quinoline phosphomolybdate to phosphorus pentoxide (P2O5);

500 - the initial volume of the sample solution, in milliliters (mL); m - the mass of the dried sample, in grams (g);

10 - the measured volume of the sample solution, in milliliters (mL).

The test result is based on the arithmetic mean of the parallel determination results. The absolute difference between two independent determination results that are obtained under repeatability conditions is not more than 0.3%. […]

A.4 Determination of loss on ignition (on a dry basis)

A.4.1 Instruments and apparatuses

A.4.1.1 Crucible.

A.4.1.2 Electrothermal constant-temperature dry box.

A.4.1.3 High temperature furnace.