GB 5009.16-2023 National food safety standard - Determination of tin in foods English
1 Scope
This standard specifies the methods for determination of tin in foods by hydride generation - atomic fluorescence spectrometry, inductively coupled plasma mass spectrometry and inductively coupled plasma - optical emission spectrometry.
This standard is applicable to the determination of tin in foods.
Method I Hydride generation - atomic fluorescence spectrometry
2 Principle
The specimen, after being digested, generates tin hydride (SnH4) under the action of sodium borohydride (or potassium borohydride) and is brought into the atomizer by the carrier gas for atomization. Under the irradiation of the tin hollow-cathode-lamp, the ground-state tin atoms are excited to an upper state, and emit fluorescence at characteristic wavelengths when de-activated and returned to the ground state, where the fluorescence intensity is directly proportional to the tin content, which is quantified by comparison with a series of standard solutions.
3 Reagents and materials
Unless otherwise specified, analytical reagents, and Class-II water as defined in GB/T 6682, are used for the purpose of this method.
3.1 Reagents
3.1.1 Sulfuric acid (H2SO4): Guaranteed reagent.
3.1.2 Nitric acid (HNO3): Guaranteed reagent.
3.1.3 Perchloric acid (HClO4): Guaranteed reagent.
3.1.4 Thiourea (CH4N2S).
3.1.5 Ascorbic acid (C6H8O6).
3.1.6 Sodium borohydride (NaBH4) or potassium borohydride (KBH4).
3.1.7 Sodium hydroxide (NaOH) or potassium hydroxide (KOH).
3.2 Reagent preparation
3.2.1 Nitric acid - perchloric acid mixed solution (4+1): Prepared by measuring out 400mL of nitric acid and 100mL of perchloric acid and mixing well.
3.2.2 Sulfuric acid solution (1+9): Prepared by measuring out 100mL of sulfuric acid, pouring it slowly into 900mL of water and mixing well.
3.2.3 Thiourea - ascorbic acid solution: Prepared by weighing out 15.0g of thiourea and 15.0g of ascorbic acid, dissolving them with water, diluting the solution to 100mL, and mixing well. To be freshly prepared before use.
3.2.4 Sodium hydroxide solution (5g/L): Prepared by weighing out 5.0g of sodium hydroxide, dissolving it with water, diluting the solution to 1,000mL, and mixing well.
3.2.5 Sodium borohydride solution (7g/L): Prepared by weighing out 7.0g of sodium borohydride, dissolving it with sodium hydroxide solution (5g/L), diluting the solution to 1,000mL, and mixing well. To be freshly prepared before use.
Note: This method may be used with potassium borohydride as the reducing agent (prepared by dissolving potassium borohydride with potassium hydroxide solution), and the concentration of sodium borohydride or potassium borohydride in the reducing agent (7g/L~20g/L) may be adjusted according to the sensitivity of the instrument.
3.3 Standard sample
Standard sample for metal tin (Sn): With a purity ≥99.99%. Alternatively, a tin standard solution of a certain concentration that has been certified by the nation and granted a standard substance certificate may be used.
3.4 Standard solution preparation
3.4.1 Tin standard solution (1.00mg/mL): Accurately weigh out 0.1000g of metal tin standard sample, put it in a small beaker, add 10.0mL of sulfuric acid and cover the beaker with the watch glass. Heat the solution until the tin is completely dissolved, remove the watch glass, continue heating the solution until white thick smoke appears. Cool the beaker, slowly add 50mL of water and move the solution into a 100mL volumetric flask. Wash the beaker several times with sulfuric acid solution (1+9), and incorporate the washing liquid into the volumetric flask. Dilute the solution to the scale and mix well.
3.4.2 Tin standard intermediate solution (10.0mg/L): Accurately pipette 1.00mL of tin standard solution (1.00mg/mL) into a 100mL volumetric flask, dilute it with sulfuric acid solution (1+9) to the scale, and mix well. Preserve it at 0℃~5℃ for a shelf period of 4 weeks.
Foreword II
1 Scope
Method I Hydride generation - atomic fluorescence spectrometry
2 Principle
3 Reagents and materials
4 Apparatus
5 Analytical procedure
6 Expression of analysis results
7 Precision
8 Others
Method II Inductively coupled plasma mass spectrometry
9 Principle
10 Reagents and materials
11 Apparatus
12 Analytical procedure
13 Expression of analysis results
14 Precision
15 Others
Method III Inductively coupled plasma - optical emission spectrometry
16 Principle
17 Reagents and materials
18 Apparatus
19 Analytical procedure
20 Expression of analysis results
21 Precision
22 Others
Annex A Temperature programming for microwave digestion
