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1 Translated English of Chinese Standard: NATIONAL STANDARD OF THE GB PEOPLE S REPUBLIC OF CHINA GB National Food Safety Standard Determination of Cadmium in Foods Issued on: January 28, 2015 Implemented on: July 28, 2015 Issued by: National Health and Family Planning Commission of the PRC Page 1 of 9

2 Table of Contents Foreword Scope Principle Reagents and Materials Apparatuses and Instruments Analytical Procedure Analytical Result Expression Precision Others Page 2 of 9

3 Foreword This Standard replaces GB/T Determination of Cadmium in Foods. Compared with GB/T , this Standard mainly has the following changes: --- Change the standard name into National Food Safety Standard: Determination of Cadmium in Foods. --- Delete the Method 2 Atomic Absorption Spectrometry, Method 3 Colorimetry, and Method 4 Atomic Fluorescence Spectrometry. Page 3 of 9

4 National Food Safety Standard Determination of Cadmium in Foods 1 Scope This Standard specifies the method for the determination of cadmium in all kinds of food by graphite furnace atomic absorption spectrometry. This Standard is applicable to the determination of cadmium in all kinds of food. 2 Principle After ashing or acid digestion of the specimen, inject certain amount of sample s digestive juice into graphite furnace of atomic absorption spectrophotometer; after the electro-thermal atomic absorption, absorb 228.8nm resonance line; within certain concentration range, the absorbance value is directly proportional to the content of cadmium; quantify it by the standard curve method. 3 Reagents and Materials NOTE 1: Unless otherwise specified, the reagents used in this method are analytical pure; while the water used is Grade-2 water stated in GB/T NOTE 2: The glassware used is required to soak in the nitric acid solution (1+4) for 24h above, repeatedly resin with water; finally, rinse with deionized water. 3.1 Reagents Nitric acid (HNO 3 ): guaranteed reagent Hydrochloric acid (HCL): guaranteed reagent Perchloric acid (HCLO 4 ): guaranteed reagent Hydrogen peroxide (H 2 O 2, 30%), Ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ). 3.2 Preparation of reagents Page 4 of 9

5 3.2.1 Nitric acid solution (1%): take 10.0mL of nitric acid, add it to 100mL of water, dilute to 1000mL Hydrochloric acid solution (1+1): take 50mL of hydrochloric acid, slowly add it to 50mL of water Nitric acid - perchloric acid mixed solution (9+1): take 9 portions of nitric acid, and mix with 1 portion of perchloric acid Ammonium dihydrogen phosphate solution (10g/L): weigh 10.0g of ammonium dihydrogen phosphate; after dissolving into 100mL of nitric acid solution (1%), quantitatively move into 1000mL flask, then dilute with nitric acid solution (1%) to the specified scale. 3.3 Reference standard material As for the reference standard material of metal cadmium (Cd): its purity is 99.99% or the standard substance authenticated nationally and awarded by the standard substance certificate. 3.4 Preparation of standard solution Cadmium standard stock solution (1000mg/L): accurately weigh 1g of metal cadmium reference standard material (accurate to g) into a small beaker; add, for several times, 20mL of hydrochloric acid solution (1+1) to dissolve; add 2 drops of nitric acid; move to the 1000mL flask; dilute with water to the scale, mix thoroughly; or purchase the standard substance authenticated nationally and awarded by standard substance certificate Cadmium standard solution (100ng/mL): absorb 10.0mL of cadmium standard stock solution into a 100mL flask; dilute with nitric acid solution (1%) to the scale; after diluting in such a way for several times, it becomes the standard solution containing 100.0ng of cadmium per liter Cadmium standard curve work solution: accurately absorb 0mL, 0.50mL, 1.0mL, 1.5mL, 2.0mL, 3.0mL of cadmium standard solution into the 100mL flasks respectively; dilute with nitric acid solution (1%) to the scale; then obtain the standard serial solutions with the cadmium content of 0ng/mL, 0.50ng/mL, 1.0ng/mL, 1.5ng/mL, 2.0ng/mL, 3.0ng/mL. 4 Apparatuses and Instruments 4.1 Atomic absorption spectrophotometer, attached with graphite furnace. 4.2 Cadmium hollow cathode lamp. Page 5 of 9

6 and dilute with nitric acid solution (1%) to the scale, mix thoroughly, and store for later use; meanwhile, do the reagent blank test. b) Microwave digestion: weigh dry specimen 0.3g~0.5g (accurate to g), fresh (wet) specimen 1g~2g (accurate to 0.001g), place them into the microwave digestion tank; add 5mL of nitric acid and 2mL of hydrogen peroxide. Microwave digestion procedure can, according to the apparatus model, adjust to the optimal condition. After the completion of the digestion, open the digestion tank after cool down; the digestive juice turns to be colorless or pale yellow; conduct heating, acid-driven till it is nearly dry; use small amount of nitric acid solution (1%) to wash the digestion tank for three times; move the solution to the 10mL or 25mL flask; dilutee with nitric acid solution (1%) to the scale; mix thoroughly, store for later use; meanwhile do the reagent blank test. c) Wet digestion method: weigh dry specimen 0.3g~0.5g (accurate to g), fresh (wet) specimen 1g~2g (accurate to 0.001g), place them into conical flask; put a few glass beads; add 10mL of nitric acid-perchloric acid mixed solution (9+1), cover the cap, and soak overnight; equip a small funnel, and digest on the electric hot plate; if it turns to be black-brown, add nitric acid till there is white smoke; when the digestive juice turns to colorless, transparent, and pale yellow; after cool down, wash the digestive juice into 10mL or 25mL flask; use small amount of nitric acid solution (1%) to wash the conical flask for three times; combine the washings into the flask, and dilute with nitric acid solution (1%) to the scale; mix thoroughly, store for later use; meanwhile do the reagent blank test. d) Dry ashing: weigh dry specimen 0.3g~0.5g (accurate to g), fresh (wet) specimen 1g~2g (accurate to 0.001g), liquid specimen 1g~2g (accurate to 0.001g), place them into the porcelain crucible; firstly use the gentle fire to carbonize till there is no smoke on the adjustable electric furnace; move into 500 C muffle furnace to do ashing for 6h~8h; then cool down. If individual specimen is not completely ashed, add 1mL of mixed acid, and heat with gentle fire on the adjustable electric furnace; after the mixed acid is evaporated, transfer to the 500 C muffle furnace to do ashing for 1h~2h again till specimen is digested thoroughly and turns to gray or light gray. Cool down, use nitric acid solution (1%) to dissolve the ash; move the specimen digestive juice into 10mL or 25mL flask; use small amount of nitric acid solution (1%) to wash the porcelain crucible for three times; combine the washings into the flask; dilute with nitric acid solution (1%) to the scale, mix thoroughly, and store for later use; meanwhile, do the reagent blank test. NOTE: Carry out experiment in a well ventilated hood. For the grease-containing sample, try to avoid using the wet digestion method to digest; preferably take the dry digestion method; if the wet digestion method is required, then the amount of the sample taken shall not exceed a maximum of 1g. Page 7 of 9