Detection of heavy metal content parameters in agricultural products

This standard specifies the graphite furnace atomic absorption spectrometry method for the determination of chromium in food. This standard is applicable to the determination of chromium content in various foods. After the digestion treatment of the sample, the absorption value was measured at 357.9 nm using graphite furnace atomic absorption spectroscopy. Within a certain concentration range, the absorption value was compared quantitatively with the standard series solution. 3 Reagent and material notes: Unless otherwise specified, the reagents used in this method are all super slow pure - water is the second grade water specified in GB/T 6682. 3.1 Reagent 3.1.1 Nitric acid (HNOs). 3.1.2 Perchlorate (HCIO), 3.1.3.3 Ammonium dihydrogen phosphate (NHH, PO), 3.2 Reagent preparation, 3.2.1 Nitric acid solution (5+95): Measure 50 rmL of nitric acid and slowly pour it into 950 mL of water, mix well. 3.2.2 Nitric acid solution (101): Measure 250 mL of nitric acid and slowly pour it into 250 mI of water, and mix well. 3.2.3- Ammonium dihydrogen phosphate solution (20 g/L); Weigh 2.0 g of ammonium dihydrogen phosphate, dissolve in water, and dilute to 100 ml. Mix well. 3.3 Standard potassium dichromate (K: Cr. O;): a standard substance with a purity of ≥ 99.5% or certified by the state and awarded a standard substance certificate. 3.4 Preparation of Standard Solution 3.4.1 Chromium Standard Stock Solution: Accurately weigh 1.431 5g (accurate to 0.000 1g) of the reference substance potassium dichromate (110 ℃, baked for 2 hours), dissolve it in water, transfer it to a 500 ml volumetric flask, dilute it to the mark with nitric acid solution (5+95), and mix well. This solution contains 1.000 mg of chromium per milliliter. Alternatively, purchase chromium standard stock solution that has been certified by the state and awarded a standard substance certificate. 3.4.2: Chromium standard solution; Dilute the chromium standard stock solution step by step with nitric acid solution (5+95) to 100 ng chromium per milliliter. 3.4.3 Preparation of standard series solutions: Take 0 mL, 0.500 mL, 1.00 mL, 2.00 mL, and 3.00 mL of chromium standard solution (100 ng/mL) into a 25 mL volumetric flask, dilute to the mark with nitric acid solution (5+95), and mix well. Each volumetric flask contains 0ng, 2.00 ng, 4.00 ng, 8.00 ng, 12.0 ng, and 16.0 ng of chromium per milliliter, respectively. Alternatively, a graphite furnace automatic sampler can be used for automatic preparation

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