GB 5009.16-2023National food safety standard - Determination of tin in foods (English PDF)

3.1 Reagents

3.2 Preparation of reagents

3.2.1 Nitric acid-perchloric acid mixed solution (4+1). Measure 400 mL of nitric acid

and 100 mL of perchloric acid, and mix well.

3.2.2 Sulfuric acid solution (1+9). Measure 100 mL of sulfuric acid, slowly add 900 mL

of water, and mix well.

3.3 Standard

Metal tin (Sn) standard product. purity >=99.99%. Or tin standard solution of a certain

concentration that is certified by the state and awarded a reference material certificate.

3.4 Preparation of standard solution

3.4.1 Tin standard solution (1.00 mg/mL). Accurately weigh 0.100 0 g of metal tin

standard; place it in a small beaker; add 10.0 mL of sulfuric acid; cover with a watch

glass; heat until the tin is completely dissolved; remove the watch glass;

3.4.2 Tin standard intermediate solution (10.0 mg/L). Accurately draw 1.00 mL of tin

standard solution (1.00 mg/mL) into a 100 mL volumetric flask; use sulfuric acid

solution (1+9) to dilute to the mark; mix well. Store at 0 °C ~ 5 °C, valid for 4 weeks.

3.4.3 Tin standard working solution (1.00 mg/L). Accurately draw 10.0 mL of tin

standard intermediate solution (10.0 mg/L) into a 100 mL volumetric flask; use sulfuric

acid solution (1+9) to dilute to the mark; mix well. Store at 0 °C ~ 5 °C, valid for 4

weeks.

4.1 Atomic fluorescence spectrometer. equipped with tin hollow cathode lamp.

4.2 Adjustable temperature control electric hot plate. temperature control range 90 °C

~ 250 °C.

4.4 Electronic balance. the sensitivity is 0.1 mg and 1 mg.

4.5 Sample crushing equipment. homogenizer, high-speed crusher.

5.1 Sample preparation

5.1.1 Solid samples

5.1.2 Liquid samples

For samples such as soft drinks and liquid condiments, shake well.

5.1.3 Semi-solid sample

Mix well.

5.2 Sample digestion

5.2.1 Weigh 1 g ~ 5 g (accurate to 0.001 g) of the sample or accurately transfer 1.00 mL

~ 5.00 mL of the liquid sample into a glass digestion vessel.

5.2.2 Accurately pipette 10.0 mL of blank solution and sample solution respectively;

place them in a 25 mL volumetric flask; add 3.0 mL of sulfuric acid solution (1+9); add

2.0 mL of thiourea + ascorbic acid solution; then, use water to adjust the volume to 25

mL; mix well to obtain blank determination solution and sample determination solution.

5.3 Apparatus reference conditions

Negative high voltage 380 V; lamp current 70 mA; atomization temperature 850 °C;

shielding gas flow 1 200 mL/min;

5.4 Preparation of the standard curve

After the instrument is preheated and stabilized, inject the standard series solution into

the atomic fluorescence spectrometer; measure the fluorescence intensity of tin; draw a

standard curve with the mass concentration of tin in the standard series solution as the

abscissa and the fluorescence intensity as the ordinate.

5.5 Determination of sample solution

Respectively inject the blank determination solution and the sample determination

solution into the atomic fluorescence spectrometer;

10.1 Reagents

10.2 Preparation of reagents

10.3 Standard

10.3.1 Tin standard solution (1 000 mg/L). Use the tin reference solution certified by

the state and awarded a reference material certificate.

10.4 Preparation of standard solution

10.4.1 Tin standard intermediate solution (10.0 mg/L). Accurately draw 1.00 mL of tin

standard solution (1 000 mg/L) into a 100 mL volumetric flask; use hydrochloric acid

solution (5+95) to dilute to the mark; mix well. Store at 0 °C ~ 5 °C, valid for 4 weeks.

10.4.2 Tin standard working solution (1.00 mg/L). Accurately draw 10.0 mL of tin

standard intermediate solution (10.0 mg/L) into a 100 mL volumetric flask; use

hydrochloric acid solution (5+95) to dilute to the mark; mix well. Store at 0 °C ~ 5 °C,

valid for 4 weeks.

10.4.4 Internal standard working solution. Take an appropriate amount of internal

standard element stock solution; use nitric acid-hydrochloric acid mixed solution

(5+1+94) to dilute it step by step to prepare an internal standard working solution of

appropriate concentration.

11.1 Inductively coupled plasma mass spectrometer.

11.2 Analytical balance. the sensitivity is 1mg.

11.4 Microwave digestion system. equipped with polytetrafluoroethylene digestion

inner tank.

11.5 Sample crushing equipment. homogenizer, high-speed crusher.

12.1 Sample preparation

Same as 5.1.

12.2 Sample digestion

Weigh 0.2 g ~ 0.5 g (accurate to 0.001 g; the sampling amount can be appropriately

increased to 1 g for samples containing more moisture) of the sample, or accurately

transfer 0.500 mL ~ 3.00 mL of the liquid sample into the microwave digestion inner

tank. For samples containing ethanol or carbon dioxide, heat at 90 °C for 30 minutes to

remove ethanol or carbon dioxide.

12.3 Apparatus reference conditions

Tin isotope 118 Sn, internal standard element 103 Rh or 185 Re; radio frequency power 1

0.90 L/min; sampling depth 10 mm; analysis mode the normal mode or

collision/reaction cell mode; repeated for 2 ~ 3 times; flushing time 60 seconds.

12.5 Test of sample solution

Inject the blank solution and sample solution into the inductively coupled plasma mass

spectrometer respectively; measure the signal response values of tin element and

internal standard element; obtain the mass concentration of tin element in the solution

according to the standard curve.