GB 5009.246-2016National food safety standard - Determination of titanium dioxide in foods (English PDF)

3.1 Reagents

3.1.1 Perchloric acid (HClO4). guaranteed reagent.

3.1.2 Sulfuric acid (H2SO4). guaranteed reagent.

3.1.3 Nitric acid (HNO3). guaranteed reagent.

3.1.4 Ammonium sulfate [(NH4)2SO4].

3.2 Preparation of reagents

3.2.1 Sulfuric acid solution (5 + 95). measure 50 mL of sulfuric acid; add slowly into

950 mL of water; mix up.

3.2.2 Mixed acid [perchloric acid + nitric acid (1 + 9)]. measure 100 mL of perchloric acid; add slowly into 900 mL of nitric acid; mix up.

3.3 Standard substance

Titanium dioxide (TiO2). primary reagent or spectrographically pure.

3.4 Preparation of standard solutions

3.4.1 Titanium standard stock solution (1,000 µg/mL). weigh 0.167 g of titanium dioxide;

add 5 g of ammonium sulfate; add 10 mL of sulfuric acid; heat to dissolve; allow to cool;

transfer to a volumetric flask of 100 mL; dilute to scale; mix up. Or use a standard solution which has passes the national certification and awarded the certificate of a standard substance.

3.4.2 Titanium standard using solution (10.0 µg/mL). absorb 1.00 mL of titanium

standard stock solution to pour into a volumetric flask of 100 mL; use sulfuric acid solution (5 + 95) to dilute to scale.

3.4.3 Titanium standard serial working solutions. absorb 0.000 mL, 0.500 mL, 2.00 mL,

5.00 mL, 10.0 mL and 20.0 mL of titanium standard using solution; pour respectively into a volumetric flask of 100 mL; use sulfuric acid solution (5 + 95) to dilute to scale;

prepare the titanium serial standard working solutions of 0.000 µg/mL, 0.050 µg/mL,

0.200 µg/mL, 0.500 µg/mL, 1.00 µg/mL and 2.00 µg/mL.

5.1 Solid and semisolid sample

10.2.1 Mixed solution [perchloric acid + nitric acid (1 + 9)]. measure 100 mL of perchloric acid; slowly add into 900 mL of nitric acid; mix up.

10.2.2 Hydrochloric acid solution (1 + 1). measure 100 mL of hydrochloric acid; slowly add into 100 mL of water; mix up.

10.2.3 Hydrochloric acid solution (1 + 23). measure 10 mL of hydrochloric acid; slowly add into 230 mL of water; mix up.

10.2.4 Sulfuric acid solution (2 + 98). measure 20 mL of sulfuric acid; slowly add into

980 mL of water; mix up.

10.2.5 Ascorbic acid solution (2%). weigh 2 g of ascorbic acid; use water to dissolve before diluting to 100 mL; prepare immediately prior to use.

10.2.6 Diantipyryl methane solution (5%). weigh 5 g of diantipyryl methane; use

hydrochloric acid solution (1 + 23) (10.2.3) to dissolve and dilute to 100 mL.

10.3 Standard substance

Titanium dioxide (TiO2). primary reagent or spectrographically pure.

10.4 Preparation of standard solutions

10.4.1 Titanium standard stock solution (1,000 µg/mL). weigh 0.167 g of titanium

dioxide; add 5 g of ammonium sulfate; add 10 mL of sulfuric acid; heat to dissolve;

allow to cool; transfer to a volumetric flask of 100 mL; dilute to scale; mix up. Or use a standard solution which has passes the national certification and awarded the certificate of a standard substance.

10.4.2 Titanium standard using solution (10 µg/mL). absorb 1.00 mL of titanium

standard stock solution (10.4.1) to pour into a volumetric flask of 100 mL; use sulfuric acid (2 + 98) to dilute to scale.

12.1 Solid and semisolid sample

use water to dilute to scale; shake up; place aside for 40 min. The concentrations of titanium in standard serial working solutions are 0.000 µg/mL, 0.100 µg/mL, 0.200

µg/mL, 0.500 µg/mL, 1.00 µg/mL and 2.00 µg/mL.

13.5 Plotting of standard curve

Use the standard blank solution after developing as the reference; use a cuvette of 1 cm; at the wavelength of 420 nm; use the ultraviolet spectrophotometer to determine the absorbance of standard serial working solutions after developing. Plot the standard curve using the concentrations of standard serial working solutions as the abscissa and the corresponding absorbances as the ordinate.

13.6 Determination

Under the same experimental conditions as those for the determination of standard solutions, determine the absorbances of sample solution and blank solution after developing. Obtain the concentrations of sample solution and blank solution based on the standard curve (13.5) and the absorbances of blank solution and sample solution.