Element and pollutant detection

This standard specifies the graphite furnace atomic absorption spectrometry, inductively coupled plasma mass spectrometry, flame atomic absorption spectrometry, and disulfide 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. After the sample is digested and treated, it is atomized in a graphite furnace and the absorbance is measured at 283.3 nm. The absorbance value of lead is directly proportional to the lead content within a certain concentration range, and is quantitatively compared to the standard series. Unless otherwise specified, all reagents and materials used in this method are high-grade pure, and the water is Grade II water as specified in GB/T 6682. 3.1 Reagent 3.1.1 Nitric acid (HNO,). 3.1.2 Hyperfluoric acid (HCIO,). 3.1.3 Ammonium dihydrogen phosphate (NHH: PO,). 3.1.4 Palladium nitrate [Pd (NO.):]. 3.2 Reagent preparation 3.2.1 Nitric acid solution (5+95); Measure 50 mL of nitric acid, slowly add to 950 mL of water, and mix 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 100mL with nitric acid solution (5+95). Mix well. 3.3 Standard lead nitrate [Pb (NO,);, CAS No. 10099-74-8]; Purity ≥ 99.99%. Or a certain concentration of lead standard solution certified by the state and awarded with a standard substance certificate. 3.4 Preparation of standard solution 3.4.1: Lead standard stock solution (l 000 mg/L): Accurately weigh 1.598 5 g (accurate to 0.000 l g) of lead nitrate, dissolve in a small amount of nitric acid solution (1+9), transfer to a 10 mL volumetric flask, add water to the mark, and mix well

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