Lead in food is a harmful element, and the lead content in soy sauce is not more than 1 mg per kg of soy sauce according to the hygienic standards of soy sauce. The content of lead in soy sauce is low and contains a lot of organic matter such as sodium chloride and amino acids. Use the atomic absorption spectrophotometer | graphite furnace atomic absorption spectrometry to detect the content of lead in soy sauce. Whether using the Zeeman effect background correction or the continuous light source background correction, good results can be obtained, and the reliability of measuring lead is improved. 1. (Atomic absorption spectrophotometer | Atomic absorption spectrometry to detect lead content in soy sauce) Test part 1.1 Main instruments and reagents Atomic absorption spectrometer, metal sleeve glass efficient atomizer, deuterium lamp background correction. Graphite furnace, pyrolysis coated graphite tube, automatic sampler (Hunan Chuangte). High-intensity lead hollow cathode lamp. 4520A atomic absorption spectrometer, horizontal DC heating graphite furnace, AC longitudinal Zeeman background correction, horizontal heating, integrated arc platform pyrolysis coated graphite tube. DK300A autosampler, Lumina lead element lamp. FR-2 all-polytetrafluoroethylene sealed pressurized microwave digestion tank. The volume is 70 ml, with explosion-proof membrane and overpressure automatic deflation and pressure relief safety protection device. When the pressure in the tank exceeds 1.2MP, the pressure is automatically relieved and maintained at 1.2MP. Nitric acid (67%): high quality and pure. Lead standard solution: 500µgPb / ml. Dilute with high-quality pure HNO3 (15%) to 100ng / ml step by step. Palladium chloride (15% nitric acid solution): 1 mg palladium per ml. 5 μl (5 μg palladium) was added for each assay and was added together with the standard or sample solution by the autosampler. Lead-free purified water. Argon: 99.9%. 1.2 Atomic absorption spectrophotometer parameters Wavelength: 283.3nm, slit L0.7. Lamp current 15mA. Inject 20μl, light control the maximum power to heat the atomization, stop the gas, and measure the peak area. 1.3 Lead Calibration Curve Lead Standard Series P-E3030AAS instrument, graphite furnace: 0.0; 20.0; 50.0; 100ngpb / ml. Dilute lead working solution (100ngpb / ml) with 15% HN03. 4520A instrument: 0.0; 20.0; 40.0; 60.0 ;; 80.0; 100.0pbng / ml. Working fluid with lead (100ngpb / ml) and 15% HN03 are used as diluent, the instrument automatically prepares. The above are fitted with linear equations. 1.4 Sample preparation Accurately weigh 2 ml of soy sauce (and weigh it) into the FR-2 digestion tank, and accurately add 3 ml of concentrated nitric acid. Close the inner cover and tighten the outer cover. Place a beaker containing 200 ml of water in the center of the microwave oven load plate, and place the digestion tank containing the sample evenly around the beaker. First heat with 60% power for 5 minutes, and then heat with 40% power for 5 minutes. Take out the digestion tank and cool to room temperature with running water. Open the digestion tank and add 15 ml of purified water accurately (total volume is 20 ml). Close the inner lid and screw the outer lid tightly, shake the digestion tank to make the solution even for the measurement. 2. (Atomic Absorption Spectrophotometer | Atomic Absorption Spectrometry for the Determination of Lead in Soy Sauce) Results and Discussion 2.1 Test solution acidity Using FR-2 all-tetrafluoroethylene sealed pressurized digestion tank and household microwave oven, 6 samples can be digested at a time. Add 3 ml of concentrated nitric acid to each sample to make a 20 ml volume. Omitting the nitric acid used to decompose the sample, the nitric acid concentration is 15%, which is conducive to the conversion of sodium chloride in the sample to sodium nitrate (9), and sodium nitrate is decomposed and removed in the ashing stage to overcome a large amount of sodium chloride Background interference. 2.2 Ashing temperature The test solution after soy sauce digestion uses palladium as an improver. On the 4520A, the graphite furnace ashing temperature is increased from 850 ° C to 1050 ° C. The background absorption value of a large amount of sodium chloride is greatly reduced and the absorption value of lead does not change much Table 2), can get very good analysis results. Because the Zeeman effect background correction was used, the ashing temperature was determined to be 950 ° C. Sofas OUTDOOR,large outdoor sofa,corner garden sofa set,garden sofa set sale Foshan Jianermei Furniture Co., Ltd , https://www.minottiitaly.com