1. Food (lead) testing

This standard specifies the graphite furnace atomic absorption spectrometry, inductively coupled plasma mass spectrometry, flame atomic absorption spectrometry, and dithizone colorimetric method for the determination of lead content in food. This standard is applicable to the determination of lead content in various types of food. The first method is graphite furnace atomic absorption spectroscopy. After sample digestion, it is atomized in a graphite furnace and the absorbance is measured at 283.3nm. The absorbance value of lead within a certain concentration range is directly proportional to the lead content, and is quantitatively compared to the standard series. Unless otherwise specified, all reagents and materials used in this method are high-grade pure. The water is Grade II water according to GB/T6682. 3.1 Reagents. 3.1.1 Nitric acid (HNO). 3.1.2 Perchlorate (HC1O.). 3.1.3 Ammonium dihydrogen phosphate (NH H2PO). 3.1.4 Palladium nitrate [Pd (NO,) 2]. 3.2 Reagent preparation 3.2.1 Nitric acid solution (5+95); Measure 50 ml of nitric acid and slowly add it to 950 ml of water, mixing well. 3.2.2 Nitric acid solution (1+9): Measure 50 ml of nitric acid, slowly add to 450 ml of water, and mix well. 3.2.3 Ammonium dihydrogen phosphate palladium nitrate solution: Weigh 0.02g of palladium nitrate, dissolve in a small amount of nitric acid solution (1+9), then add 2g of ammonium dihydrogen phosphate, dissolve, and dilute to 100 mL with nitric acid solution (5+95), mix well. 3.3 Standard lead nitrate [Pb (N03):, CAS number: 10099-74-8]: Purity> 999%. Or a lead standard solution with a certain concentration that has been certified by the country and certified as a standard substance. 3.4 Preparation of standard solution 3.4.1 Lead standard stock solution (1000 mg/L): Accurately weigh 1.598 5 g (accurate to 0.001 g) of lead nitrate, dissolve with a small amount of nitric acid solution (1+9), transfer to a 1000 mL volumetric flask, add water to the mark, and mix well

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