GB/T 5009.62-2003Method for analysis of hygienic standard of ceramics for food contact (English PDF)

7.1 Atomic absorption spectrometry

7.1.1 Principle The cadmium ion in soak solution shall be led into the atomic absorption spectrophotometer and atomized; absorb 228.8 nm resonance line; the absorbed dose is proportional to the cadmium content; it shall be quantified through comparison with the standard series.

7.1.2 Reagent

7.1.2.1 Cadmium standard solution. accurately weigh out 0.1142 g of cadmium oxide; add 4 mL of glacial acetic acid; dissolve them by slowly heating; cool it down; transfer the solution into a 100mL volumetric flask; dilute with water to the scale; 1mL of this solution is equivalent to

1.00 mg of cadmium.

7.1.2.2 Standard cadmium working solution. suck

1.0 mL of standard cadmium solution; pour it into a 100 mL volumetric flask; dilute it with acetic acid (4%) to the scale. Per millilitre of this solution is equivalent to 10.0 µg of cadmium.

7.1.3 Instrument Atomic absorption spectrophotometer.

7.1.4 Analysis procedure

7.1.4.1 Preparation of standard curve. suck 0mL, 0.50mL, 1.00mL, 3.00mL, 5.00mL,

10.00 mL of standard cadmium working solution respectively; pour them into 100ml volumetric flasks respectively; dilute with acetic acid (4%) to the scale; mix uniformly; per millilitre of these solutions are equivalent to 0µg, 0.05µg, 0.10µg, 0.30µg, 0.50µg, 0.70µg and 1.00 µg of cadmium respectively. Calibrate the atomic

7.2.2.2 Sodium hydroxide-potassium cyanide solution (No. 1). Weigh out 400 g of sodium hydroxide and 10 g of potassium cyanide; dissolve them in water; dilute to 1000ml.

7.2.2.3 Sodium hydroxide-potassium cyanide solution (No. 2). Weigh out 400 g of sodium hydroxide and

0.5 g of potassium cyanide; dissolve them in water, dilute to 1000ml.

7.2.2.4 Dithizone-trichloromethane solution (0.1g/L).

7.2.2.5 Dithizone-trichloromethane solution (

0.02 g/L).

7.2.2.6 Sodium potassium tartrate solution (250 g/L).

7.2.2.7 Hydroxylamine hydrochloride solution (200 g/L).

7.2.2.8 Tartaric acid solution (20 g/L). store it in refrigerator.

7.2.2.9 Standard cadmium working solution. the same as 7.1.2.2.

7.2.3 Instrument Visible spectrophotometer.

7.2.4 Analysis procedure Take two piece of 125 mL separating funnels; add

0.5 mL of standard cadmium working solution (equivalent to 5 µg of cadmium) and

9.5 mL of acetic acid (4%) into one separating funnel; add 10mL of sample soak solution into the other one. Add 1 mL of sodium potassium tartrate solution, 5 mL of sodium hydroxide-potassium cyanide solution (No. 1), and 1 mL of hydroxylamine hydrochloride solution into the two separating funnels respectively. Shake the solution uniformly after adding all reagents above. Add 15mL of dithizone-trichloromethane solution (

0.1 g/L); shake for 2min (this step shall be rapidly conducted). Take another set of separating funnels; add 25mL of tartaric acid solution respectively; pour the dithizone-trichloromethane solution in the former set of separating funnels into the latter set of separating funnels; wash the former set of separating funnels with 10mL of trichloromethane; pour the trichloromethane cleaning solution into the latter set of separating funnels. Shake the latter set of separating funnels for 2min; discard the dithizone-trichloromethane solution; add 6 mL of trichloromethane respectively; shake and discard the trichloromethane layer. Add

1.0 mL of hydroxylamine hydrochloride solution;

15.0 mL of dithizone-trichloromethane solution (

0.02 g/L) and 5 mL of sodium hydroxide-potassium cyanide solution (No.2) into the aqueous solution in separating funnels respectively; shake immediately for 2min. Wipe and dry the internal wall of the lower pipe of separating funnels; insert a small amount of absorbent cotton in order to filter the globule. Pour the dithizone-trichloromethane solution into the 25mL colorimeter tubes-with-plugs, and conduct colour comparison. The degree of red of sample tube must not be larger than that of the standard tube. Otherwise, calibrate the zero point of 3 cm cuvette with trichloromethane; measure the absorbance at point where the wave length is 518 nm; and conduct quantitation.

7.2.5 Result Calculation It shall be the same as 6.2.3.