Pretreating and calibrating method for sequentially determining content of lead and cadmium elements in rice

Abstract

The invention discloses a pretreating and calibrating method for sequentially determining the content of lead and cadmium elements in rice, which comprises the following steps: (1) removing impurities of the rice, decorticating and crushing; (2) adding the processed rice into a concentrated nitric acid to be soaked for the night; moving the soaked rice into an electric hot plate to be heated and digested; adding deionized water for removing acid and obtaining a sample solution A by using the deinoized water for transferring and metering the volume; (3) using the national standard stock solution of the lead for being manufactured into series lead standard solution, determining the light absorption value of the lead and making a lead calibration curve; (4) determining the light absorption value of the sample solution A, fining the concentration of the lead in the sample solution A from the lead calibration curve, and obtaining the content of the lead in the sample by computing; (5) diluting the sample solution A by the deinoized water to obtain a sample solution B; (6) using the national standard stock solution of the cadmium for being manufactured into series cadmium standard solution, determining the light absorption value of the cadmium and making a cadmium calibration curve; and (7) determining the light absorption value of the sample solution B, fining the concentration of the cadmium in the sample solution B from the cadmium calibration curve, and obtaining the content of the cadmium in the sample by computing.

Description

technical field [0001] The invention belongs to the technical field of detection, in particular to a pretreatment and calibration method for sequentially measuring the content of lead and cadmium pollution elements in rice. Background technique [0002] At present, the pretreatment methods used in the determination of heavy metal elements in grains by atomic absorption spectrophotometer graphite furnace method include: wet digestion, dry digestion, pressure digestion tank digestion and microwave digestion and other digestion methods. Dry digestion is to weigh the sample in a crucible first, burn it on an electric furnace until it is smokeless, and carbonize completely, and then put it in a muffle furnace at 550 to 600 degrees Celsius for complete ashing for about 5 hours, and finally take out the crucible Muffle furnace, after cooling, add nitric acid to dissolve, then transfer to constant volume. The advantage of this method is that it has the advantages of low blank and l...

AI Technical Summary

Problems solved by technology

The advantage of this method is that it has the advantages of low blank and little interference during the measurement on the computer, but its disadvantage is that the digestion process is not easy to be controlled by the operator, and the process may cause the loss of measurement elements, resulting in low measurement results; pressure digestion Tank digestion is to weigh the sample into a pressure digestion inner cup of about 100 ml, add mixed acid to about one-fifth to one-fourth of the inner cup, put on a metal outer cup, screw it tightly, and put it in the oven In the middle, control the temperature of 80 to 160 degrees Celsius and bake for about 4 hours, take it out, cool it, and catch the acid on a low-temperature electric heating plate, and then transfer it to a constant volume

The principle of this method is similar to the simple wet digestion method. Because the system is airtight, it has the advantage of being less prone to loss. However, because the pressure digestion tank itself is heavy in weight, large in volume and relatively high in cost, it is difficult to process a large number of samples at the same time. There are many mixed acids, it takes a long time to catch the acid, the process is difficult to grasp, and the pressure digestion tank is used for too long and there is a danger of explosion after being placed in the oven; the microwave digestion process is similar to the pressure digestion tank digestion, the sample is first weighed to the designed After sealing the container, put it into the microwave digestion furnace, use the computer to control the program to raise the temperature, digest slowly, take it out and cool it, remove the acid, transfer to a constant volume

The advantage of this method is the same as that of pressure digestion tank digestion. The digestion process is not easy to suffer losses, but the equipment cost of microwave digestion furnace is high. The domestic equipment costs about 50,000 to 80,000 yuan, while the imported equipment costs 30,000 to 400,000 yuan. If the process control is not good , there is still a risk of explosion

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