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GB 5009.16-2023: National food safety standard - Determination of tin in foods
GB 5009.16-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National food safety standard - Determination of tin in foods
ISSUED ON: SEPTEMBER 06, 2023
IMPLEMENTED ON: MARCH 06, 2024
Issued by: National Health Commission of the People’s Republic of China;
State Administration for Market Regulation.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Principle ... 4
3 Reagents and materials ... 4
4 Instruments and apparatuses ... 6
5 Analysis steps ... 6
6 Expression of analysis results ... 8
7 Precision ... 8
8 Others ... 9
9 Principle ... 9
10 Reagents and materials ... 9
11 Instruments and apparatuses ... 10
12 Analysis steps ... 11
13 Expression of analysis results ... 12
14 Precision ... 12
15 Others ... 13
16 Principle ... 13
17 Reagents and materials ... 13
18 Instruments and apparatuses ... 14
19 Analysis steps ... 14
20 Expression of analysis results ... 15
21 Precision ... 16
22 Others ... 16
Appendix A Microwave digestion heating program ... 17
National food safety standard - Determination of tin in foods
1 Scope
This Standard specifies the methods for the determination of tin in foods by hydride
atomic fluorescence spectrometry, inductively coupled plasma mass spectrometry and
inductively coupled plasma-atomic emission spectrometry.
This Standard applies to the determination of tin in foods.
Method I – Hydride atomic fluorescence spectrometry
2 Principle
After the sample is digested, tin hydride (SnH4) is generated 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 a tin hollow cathode lamp, the ground state
tin atoms are excited to an upper state. When deactivated and returned to the ground
state, they emit fluorescence of a characteristic wavelength. The fluorescence intensity
is proportional to the tin content and can be compared quantitatively with a standard
series of solutions.
3 Reagents and materials
Unless otherwise specified, all the reagents used in this method are analytical reagents,
and the water used is grade-II water as specified by GB/T 6682.
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 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.
3.2.3 Thiourea + ascorbic acid solution: Weigh 15.0 g of thiourea and 15.0 g of ascorbic
acid, use water to dissolve and dilute to 100 mL, and mix well. Prepare when necessary.
3.2.4 Sodium hydroxide solution (5 g/L): Weigh 5.0 g of sodium hydroxide, use water
to dissolve and dilute to 1 000 mL, and mix well.
3.2.5 Sodium borohydride solution (7 g/L): Weigh 7.0 g of sodium borohydride, use
sodium hydroxide solution (5 g/L) to dissolve and dilute to 1 000 mL, and mix well.
Prepare when necessary.
Note: Alternatively, use potassium borohydride as the reducing agent (dissolved and
prepared with potassium hydroxide solution) in this method, and adjust the
concentration of sodium borohydride or potassium borohydride in the reducing
agent according to the sensitivity of the instrument (7 g/L ~ 20 g/L).
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; continue to
heat until thick white smoke appears; cool; slowly add 50 mL of water; transfer to a 100
mL volumetric flask; use sulfuric acid solution (1+9) to wash the beaker several times;
merge the cleaning mixture into the volumetric flask; dilute to the mark; mix well .
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.
3.4.4 Tin standard series solutions: Respectively take 0 mL, 0.500 mL, 2.00 mL, 3.00
mL, 4.00 mL, and 5.00 mL of tin standard working solution (1.00 mg/L) into 25 mL
volumetric flasks; respectively add 5.00 mL, 4.50 mL, 3.00 mL, 2.00 mL, 1.00 mL, and
0.00 mL of sulfuric acid solution (1+9); add 2.0 mL of thiourea + ascorbic acid solution;
Take the entire edible content (including the edible liquid part) and make it into a
homogenate or uniform powder.
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. Heat samples containing
ethanol or carbon dioxide at 90 °C for 30 minutes to remove the ethanol or carbon
dioxide. Add 10.0 mL of nitric acid-perchloric acid mixed solution (4+1); add 1.0 mL
of sulfuric acid; digest on an electric hot plate or graphite digestion device. If the
digestion solution turns brown and black during the digestion process, take it out
immediately and let it cool. Add nitric acid or nitric acid-perchloric acid mixed solution
(4+1) appropriately before continuing the digestion. When the digestion solution emits
white smoke and appears colorless, transparent or slightly yellow, continue to heat until
the remaining volume is about 1 mL; remove and cool; use water to dilute to 50 mL;
mix well and set aside to obtain a sample solution. According to the tin content in the
sample solution, use water to dilute the sample solution to an appropriate concentration
when necessary, and add a certain amount of sulfuric acid solution (1+9) during the
dilution process, so that the sulfuric acid concentration of the final sample solution is
the same as that of the standard series solution. Do a blank test at the same time.
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; carrier gas flow 500 mL/min; measurement method
the standard curve method; reading method the peak area; delay time 1 s; reading time
15 s; liquid-adding time 8 second...