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This standard replaces the determination of cadmium migration in GB/T 5009.62-2003 Method for Analysis of Hygienic Standard of Ceramics for Food Containers, GB/T 5009.63-2003 Method for Analysis of Hygienic Standard of Enamel for Food Containers, GB/T 5009.72-2003 Method for Analysis of Hygienic Standard of Aluminum-wares for Food Use, GB/T 5009.81-2003 Method for Analysis of Hygienic Standard of Stainless Steel Food Containers and Table Wares, GB/T 3534-2002 Standard Testing Methods for Lead and Cadmium Release from Domestic Ceramic, GB 8058-2003 Standard Permissible Limits and Testing Method for Release of Lead or Cadmium from Ceramic Cookware, SN/T 2597-2010 Determination of Lead, Cadmium, Chromium, Arsenic, Antimony, Germanium Migration Quantity in Polymer for Food Contact Materials - Inductively Coupled Plasma Atomic Emission Spectrometry Method, SN/T 2829-2011 Food Contact Materials for Export – Metal Materials - Determination of Migrant Heavy Metals in Food Simulants – Inductively Coupled Plasma Atomic Emission Spectrometric Method and SN/T 2886-2011 Food Contact Materials for Export - Glasswork - Determination of Lead and Cadmium in Food Simulants – Flame Atomic Absorption Spectrometry (FAAS).
The following main changes have been made with respect to GB/T 5009.62-2003 (the previous edition):
——Standard name is revised as "National Food Safety Standard - Food Contact Materials and Articles - Determination of Cadmium Migration";
——Graphite furnace atomic absorption spectrometry is added;
——Inductively coupled plasma mass spectrometry is added;
——Inductively coupled plasma emission spectrometry is added;
——Dithizone colorimetry is deleted.
National Food Safety Standard
Food Contact Materials and Articles – Determination of Cadmium Migration
1 Scope
This standard specifies the graphite furnace atomic absorption spectrometry, inductively coupled plasma mass spectrometry, inductively coupled plasma emission spectrometry and flame atomic absorption spectrometry for the determination of cadmium migration in food contact materials and articles after being soaked in food simulants.
This standard is applicable to the determination of cadmium migration in food contact materials and articles.
Method I Graphite Furnace Atomic Absorption Spectrometry
2 Principle
Soak the parts of the food contact materials and articles which are expected to contact with food in food simulants, atomize the soak solution in the graphite furnace; within certain concentration range, the absorption value determined at 228.8nm is in direct proportion to the cadmium content and is compared with standard series for quantification.
3 Reagents and Materials
Unless otherwise specified, guaranteed reagents and Class-II water (defined in GB/T 6682) are adopted for the purpose of this method.
3.1 Reagents
3.1.1 Nitric acid (HNO3).
3.1.2 Ammonium dihydrogen phosphate (NH4H2PO4).
3.1.3 Reagents required for preparation of food simulants: in accordance with the requirements of GB 31604.1.
3.2 Preparation of reagents
3.2.1 Food simulants: prepared according to the requirements of GB 5009.156.
3.2.2 Nitric acid solution (1+9): measure 10mL nitric acid, add into 90mL water and mix uniformly.
3.2.3 Nitric acid solution (5+95): pipet 50mL nitric acid, add into 950mL water and mix uniformly.
3.2.4 Ammonium dihydrogen phosphate solution (20g/L): weigh 2.0g ammonium dihydrogen phosphate, dissolve in water and scale the volume to 100mL.
3.3 Standard product
Cadmium chloride (CdCl2· H2O, CAS No.: 7790-78-5): with purity >99.99%, or cadmium standard solution in certain concentration approved and awarded with reference material certificate by the State.
3.4 Preparation of standard solutions
3.4.1 Cadmium standard stock solution (100.0mg/L): accurately weigh 0.2032g (accurate to 0.0001g) cadmium chloride, dissolve in a small amount of nitric acid solution (1+9), transfer into 1000mL volumetric flask, add water to the scale and mix uniformly.
3.4.2 Cadmium standard intermediate solution (100μg/L): pipet 1.00mL cadmium standard stock solution into a 1000mL volumetric flask, add nitric acid solution (5+95) to the scale and mix uniformly.
3.4.3 Cadmium standard series solution: accurately pipet 0mL, 0.500mL, 1.00mL, 2.00mL, 3.00mL and 4.00mL cadmium standard intermediate solutions (100μg/L) in 100mL volumetric flasks respectively, add corresponding food simulants to the scale and mix uniformly. Mass concentrations of this standard solution series are 0μg/L, 0.500μg/L, 1.00μg/L, 2.00μg/L, 3.00μg/L and 4.00μg/L.
Note: the specific concentration of cadmium in standard solution series may be determined according to the sensitivity and linear range of instruments and the actual concentration of cadmium in the soak solution. If the selected food simulant is neutral or alkaline, then appropriate amount of nitric acid shall be added to make the concentration of nitric acid in such solution be about 5% (volume fraction).
4 Instruments and Apparatus
Note: all glassware shall be soaked in nitric acid solution (1+5) overnight, flushed with tap water repeatedly, and finally washed clean with water.
4.1 Graphite furnace atomic absorption spectrometer: equipped with graphite furnace atomizer and cadmium hollow cathode lamp.
4.2 Analytical balance: with sensibility of 0.1mg.
5 Analysis Steps
5.1 Specimen pretreatment
Carry out migration test according to the intended use and service conditions of to-be-tested sample and the migration test methods and conditions specified in GB 5009.156 and GB 31604.1. After fully mixing the soak solution, take some soak test solution for analysis. If the soak test solution is neutral or alkaline, then add appropriate amount of nitric acid to make the concentration of nitric acid in such test solution be about 5% (volume fraction). Meanwhile, carry out the specimen blank test.
5.2 Determination
5.2.1 Reference conditions of instruments
See Table A.1 for the reference conditions of instruments.
5.2.2 Plotting of standard curve
Simultaneously inject 10μL cadmium standard series solution and 5μL ammonium dihydrogen phosphate solution (20g/L) (optimum injection volume may be determined according to the adopted instrument) from low concentration to high concentration into the graphite furnace, determine the absorbance value, plot a standard curve, with the concentration of the standard series as x-axis and the corresponding absorbance value as y-axis.
5.2.3 Determination of specimen solution
Simultaneously inject 10μL blank solution, specimen soak solution and 5μL ammonium dihydrogen phosphate solution (20g/L) (optimum injection volume may be determined according to the adopted instrument) into the graphite furnace, determine the absorbance value after atomization, compare with standard series for quantification.
6 Expression of Analysis Results
Obtain the concentration of cadmium in specimen solution from standard curve, and calculate migration according to GB 5009.156 after deduction of blank value to obtain the migration of cadmium in food contact materials and articles. Three significant figures are reserved for the calculation results.
7 Accuracy
The absolute difference of the results from two independent determinations under repeatability condition shall not exceed 20% of their arithmetic average.
Foreword i
1 Scope
2 Principle
3 Reagents and Materials
4 Instruments and Apparatus
5 Analysis Steps
6 Expression of Analysis Results
7 Accuracy
8 Other
9 Principle
10 Reagents and Materials
11 Instruments and Apparatus
12 Analysis Steps
13 Expression of Analysis Results
14 Accuracy
15 Other
Annex A Reference Temperature Rise Procedures of Graphite Furnace Atomic Absorption Spectrometer
Annex B Operating Reference Conditions of Flame Atomic Absorption Spectrometer
