SN/T 2210-2021 PDF in English
SN/T 2210-2021 (SN/T2210-2021, SNT 2210-2021, SNT2210-2021)
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Determination of hexavalent chromium in foods for export
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Standards related to: SN/T 2210-2021
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SN/T 2210-2021: PDF in English (SNT 2210-2021) SN/T 2210-2021
SN
ENTRY-EXIT INSPECTION AND QUARANTINE INDUSTRY
STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA
ICS 67.050
CCS X 04
Replacing SN/T 2210-2008
Determination of hexavalent chromium in foods for export
ISSUED ON: NOVEMBER 22, 2021
IMPLEMENTED ON: JUNE 01, 2022
Issued by: General Administration of Customs of the People's Republic of China
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 4
4 Method summary ... 4
5 Reagents and materials ... 4
6 Instruments and equipment ... 5
7 Specimen preparation and storage ... 6
8 Determination steps ... 6
9 Result calculation and expression ... 7
10 Limit of quantitation, recovery rate and precision ... 8
11 Method summary ... 8
12 Reagents and materials ... 8
13 Instruments and equipment ... 9
14 Sample preparation and storage ... 9
15 Determination steps ... 9
16 Result calculation and expression ... 10
17 Limit of quantitation, recovery and precision ... 11
Annex A (informative) Working conditions of inductively coupled plasma mass
spectrometry ... 12
Annex B (informative) Standard solution chromatogram ... 13
Annex C (informative) Addition recovery rate and precision of hexavalent chromium
in different samples (n=6) ... 14
Determination of hexavalent chromium in foods for export
1 Scope
This document specifies the determination method for hexavalent chromium in foods
for export.
This document is applicable to the determination of hexavalent chromium in health
foods, cereals, vegetables, meat, aquatic products, candy and other foods.
2 Normative references
The following referenced documents are indispensable for the application of this
document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
GB/T 6682, Water for analytical laboratory use -- Specification and test methods
3 Terms and definitions
There are no terms or definitions to be defined in this document.
Method One -- High performance liquid chromatography-inductively coupled
plasma mass spectrometry
4 Method summary
The chromate ions (CrO42-) in the sample are extracted using dipotassium hydrogen
phosphate buffer solution (0.1 mol/L) with a pH of 7.9~8.1. After high-speed
centrifugation, it is passed through a 0.45 μm filter membrane for high-performance
liquid chromatography-inductively coupled plasma mass spectrometry measurement.
Quantify by external standard method.
5 Reagents and materials
Unless otherwise stated, all reagents used are analytically pure, and the water is grade
one water specified in GB/T 6682.
5.1 Nitric acid (p=1.42 g/mL): guaranteed reagent.
5.2 Dipotassium hydrogen phosphate.
5.3 Ammonia.
5.4 n-Hexane.
5.5 Dipotassium hydrogen phosphate buffered extraction solution (0.1 mol/L): Dissolve
22.822 g of dipotassium hydrogen phosphate in water. Add nearly 1000 mL of water.
Mix well. Use phosphoric acid solution or potassium hydroxide solution to adjust the
pH to pH 7.9 ~8.1. Set the volume to 1000 mL.
5.6 Hexavalent chromium standard solution: 100 mg/L hexavalent chromium standard
solution. It is certified reference material.
5.7 Hexavalent chromium standard stock solution: Dilute the hexavalent chromium
standard stock solution with water step by step to a 100 μg/L solution. Prepare when
needed.
5.8 Hexavalent chromium standard curve solution: Pipette 0 mL, 0.125 mL, 0.5 mL,
1.25 mL, 2.5 mL, and 5 mL of standard stock solution (5.7) into 25 mL volumetric
flasks. Set the volume up to the mark with water. Mix well. The standards of this
standard series are: 0 μg/L, 0. 5 μg/L, 2 μg/L, 5 μg/L, 10 μg/L, and 20 μg/L. Prepare
when needed.
5.9 Mobile phase (56 mmol/L nitric acid-67 mmol/L ammonia, pH 9.0): Accurately
pipet 2.00 mL of nitric acid and 2.50 mL of ammonia solution into a beaker. Add nearly
500 mL of water. Mix well. Adjust the pH to 9.0 with ammonia or nitric acid solution,
and transfer it to a 500 mL volumetric flask. Set the volume to the mark with water.
Conduct ultrasonic degassing for 10 min.
6 Instruments and equipment
6.1 High performance liquid chromatography-inductively coupled plasma mass
spectrometer.
6.2 Ultrasonic generator.
6.3 Vortex mixer.
6.4 Oscillator.
6.5 Refrigerated centrifuge: the rotation speed is greater than 10000 r/min; the
minimum temperature is less than 4℃.
6.6 Analytical balance: sensitivity is 1 mg.
7 Specimen preparation and storage
7.1 Specimen preparation
Take about 500 g of representative sample from all the samples taken. Grind solid
samples to powders. Those with high moisture content are beaten into a paste. Mix well.
Divide into two equal portions. Put them into clean containers separately. Seal them as
specimens. Indicate the mark.
For health care capsule samples, discard the capsule shell and remove the entire
contents.
7.2 Specimen storage
Specimens with high moisture content shall be frozen and stored below -18°C.
8 Determination steps
8.1 Sample processing
Weigh 0.5 g of powder sample and 0.5 g~1.0 g (accurate to 0.001 g) of the sample with
high moisture content in a 50 mL centrifuge tube. Add dipotassium hydrogen phosphate
extraction solution (5.5). Dilute to 25 mL. The sample is vortexed for 2 min, ultrasonic
extracted for 20 min, extracted on a shaking table for 30 min, and centrifuged at 10000
r/min for 5 min. Take 4 mL of the supernatant into a 15 mL centrifuge tube. Add 1 mL
of n-hexane. Then conduct high-speed centrifugation at 10000 r/min for 5 min. Remove
2 mL of supernatant. Pass through a 0.45 μm aqueous phase filter membrane and wait
for measurement on the machine. Complete the measurement within 2 h.
8.2 Determination
8.2.1 Liquid chromatography reference conditions
Liquid chromatography reference conditions are listed below:
a) Chromatographic column: anion exchange column, 250 mm × 4.1 mm (inner
diameter), 10 μm, or one with equivalent performance.
b) Mobile phase: 56 mmol/L nitric acid-67 mmol/L ammonia, pH 9.0 (5.9).
c) Flow rate: 1.0 mL/min.
d) Injection volume: 50 μL.
8.2.2 Inductively coupled plasma-mass spectrometry conditions
10 Limit of quantitation, recovery rate and precision
10.1 Limit of quantification (LOQ)
The limit of quantitation of this method is 0.05 mg/kg.
10.2 Recovery rate and precision
The recovery and precision results of this method at the added concentration are shown
in Table C.1.
Method Two -- Ion chromatography post-column derivatization
11 Method summary
Use dipotassium hydrogen phosphate buffer solution (0.1 mol/L) with pH 7.9~8.1 to
extract chromate ions (CrO42-) in the specimen. After high-speed centrifugation, the
extract is filtered through a 0.45 μm filter. Interfering substances are separated by ion
chromatography. Mix with derivatization reagent (diphenylcarbazide). Utilizing the
strong oxidizing property of chromate, diphenylcarbazide is oxidized in an acidic
environment and complexed into a purple-red complex. The absorbance is measured at
540 nm. Use external standard method to quantify.
12 Reagents and materials
Unless otherwise stated, all reagents used are analytically pure, and the water is grade
one water specified in GB/T 6682.
12.1 Nitric acid (p =1.42 g/mL): guaranteed reagent.
12.2 Dipotassium hydrogen phosphate.
12.3 Ammonia.
12.4 n-Hexane.
12.5 Methanol: chromatographically pure.
12.6 Sulfuric acid (p =1.84 g/mL).
12.7 Diphenylcarbohydrazide: chromatographically pure.
12.8 Dipotassium hydrogen phosphate buffer solution (0.1 mol/L): see (5.5).
12.9 2 mol/L sulfuric acid solution: Measure 108.7 mL of concentrated sulfuric acid.
Slowly transfer into a beaker containing approximately 800 mL of water. Stir constantly
while doing so. After the solution cools to room temperature, transfer it to a 1000 mL
volumetric flask. Add water to the mark.
12.10 Post-column derivatization solution: Weigh 0.4 g of diphenylcarbazide. Dissolve
with 50 mL of methanol. Transfer to a 500 mL volumetric flask. Measure 50 mL of 2
mol/L sulfuric acid and add it to the 500 mL volumetric flask. Shake well. Add water
to set the volume to the mark.
12.11 Hexavalent chromium standard solution: 100 mg/L hexavalent chromium
standard solution. It is certified reference material.
12.12 Hexavalent chromium standard stock solution: see (5.7).
12.13 Hexavalent chromium standard curve solution: see (5.8).
12.14 Mobile phase: Accurately pipet 2.5 mL of nitric acid and 3.5 mL of ammonia
solution into a 500 mL volumetric flask. Use water to set the volume to the mark.
Conduct ultrasonic degassing for 10 min.
13 Instruments and equipment
13.1 Ion chromatograph with post-column derivatization device, diode array or UV-
visible detector.
13.2 Ultrasonic generator.
13.3 Vortex mixer.
13.4 Oscillator.
13.5 Refrigerated centrifuge: the rotation speed is greater than 10000 r/min; the
minimum temperature is less than 4℃.
13.6 Analytical balance: sensitivity is 1 mg.
14 Sample preparation and storage
See Chapter 7.
15 Determination steps
15.1 Sample processing
See 8.1.
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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