GB 1886.336-2021National food safety standard - Food additives - Sodium dihydrogen phosphate (English PDF)

2.1 Molecular formula

Sodium dihydrogen phosphate anhydrous: NaH2PO4

Sodium dihydrogen phosphate monohydrate: NaH2PO4·H2O

Sodium dihydrogen phosphate dihydrate: NaH2PO4·2H2O

2.2 Relative molecular mass

Sodium dihydrogen phosphate anhydrous: 119.98 (according to 2018 international relative atomic mass)

Sodium dihydrogen phosphate monohydrate: 137.99 (according to 2018 international relative atomic mass)

Sodium dihydrogen phosphate dihydrate: 156.01 (according to 2018 international relative atomic mass)

3.1 Sensory requirements

The sensory requirements shall meet the requirements of Table 1.

A.1 General

The reagents and water used in this Standard refer to analytically-pure reagents and grade three water specified in GB/T 6682 when other requirements are not indicated. All standard solutions, preparations and products for the determination of impurities used in the test, when no other requirements are specified, are prepared according to GB/T 601, GB/T 602, GB/T 603. The solution used refers to an aqueous solution when it is not specified which solvent is used for preparation.

A.2 Identification test

A.2.1 Reagents and materials

A.2.1.1 Ammonia solution: 2+3.

A.2.1.2 Nitric acid solution: 1+8.

A.2.1.3 Silver nitrate solution: 17g/L.

A.2.2 Identification method

A.2.2.1 Identification of phosphate

Weigh 1g of specimen. Dissolve in 20mL of water. Add silver nitrate solution.

Generate yellow precipitate. This precipitate can be dissolved in ammonia solution or nitric acid solution.

A.2.2.2 Identification of sodium ion

Weigh 1g of specimen. Add 20mL of water to dissolve. Dip a platinum wire ring in hydrochloric acid. Burn to colorless on the flame. Dip the test solution and burn on the flame. The flame shall be bright yellow.

A.3 Determination of sodium dihydrogen phosphate (NaH2PO4) (on a dry basis) content

Where, 5.0 - The volume of hydrochloric acid standard titration solution added, in milliliters (mL); c1 - The concentration of hydrochloric acid standard titration solution, in moles per liter (mol/L);

V - The volume of sodium hydroxide standard titration solution consumed when titrating to pH~4.0 when the sudden jump occurs, in milliliters (mL); c2 - The concentration of sodium hydroxide standard titration solution, in moles per liter (mol/L).

When V1< 0, the mass fraction w1 of sodium dihydrogen phosphate (NaH2PO4) is calculated according to formula (A.2).

When V1>=0, the mass fraction w1 of sodium dihydrogen phosphate (NaH2PO4) is calculated according to formula (A.3).

Where, V2 - The volume of sodium hydroxide standard titration solution consumed for titration between pH~4.0 and pH~8.8, in milliliters (mL); c2 - The concentration of sodium hydroxide standard titration solution, in moles per liter (mol/L);

V1 - The volume of hydrochloric acid standard titration solution consumed when titrated to pH~4.0 when a sudden jump occurs, in milliliters (mL); c1 - The concentration of hydrochloric acid standard titration solution, in moles per liter (mol/L);

M - The molar mass of sodium dihydrogen phosphate (nah2po4), in grams per mole (g/mol) (M = 119.98);

10-3 - The conversion factor; m1 - The specimen mass, in grams (g).

A.5.3 Result calculation

The mass fraction w3 of water-insoluble matter is calculated according to formula (A.5).

Where, m4 - The mass of water insoluble matter and glass sand crucible, in grams (g); m5 - The mass of glass sand crucible, in grams (g); m6 - The mass of specimen, in grams (g); w2 - The mass fraction of loss on drying determined according to A.4, %.

The test results are based on the arithmetic mean of the parallel determination results. The absolute difference between two independent determination results obtained under repeatability conditions is not more than 0.01%.

A.6 Determination of pH (10g/L aqueous solution)

A.6.1 Reagents and materials

Carbon dioxide-free water.

A.6.2 Instruments and equipment

Acidity meter: Resolution is 0.01pH; equipped with glass electrode and saturated calomel electrode (or composite electrode).

A.6.3 Analysis steps

Weigh 1.00g±0.01g of specimen. Place in a 100mL beaker. Use carbon dioxide-free water to dissolve. Transfer to a 100mL volumetric flask. Use carbon dioxide-free water to dilute to the scale mark. Shake well. Pour into a 100mL dry beaker. Use a calibrated acid meter to determine the pH of the test solution. […]