Determination of chromium in gelatin by graphite furnace atomic absorption spectrometry

Determination of chromium in gelatin by graphite furnace atomic absorption spectrometry

Key words: atomic absorption spectrometer; chromium in gelatin; ; AA1800 high chromium gelatin can be widely used in skin jelly, milk sugar, gelatin gelatin, marshmallow, ice cream, yogurt, ham, medicine "Pills, pharmaceutical capsules, alcohol and soy sauce, etc." is a kind of "additive for food and medicine", and is also the main material for the production of capsules. However, recent media reports on the use of capsule chromium exceeding the standards of many manufacturers' drugs have caused society. Widespread attention from all walks of life. With the intensified events of “toxic capsules” and chromium in gelatin, it is of great significance to accurately detect the chromium content in gelatin. This test experiment uses high pressure digestion to digest samples according to relevant experiments and national standards. Wet digestion and dry digestion are difficult to eliminate, and the chromium content in gelatin is quickly detected by graphite furnace atomic absorption spectrometry. 1. Experimental Part 1.1 Apparatus and Working Conditions AA1800 Atomic Absorption Spectrophotometer (ME) Hollow cathode lamp; ultrapure water machine. Instrument operating parameters: wavelength 357.9nm, current 5mA, slit 0.4nm.1.2 main reagent nitric acid (excellent Pure); hydrogen peroxide (excellent grade); chromium standard solution; ammonium dihydrogen phosphate (superior pure) 1.3 sample processing method sample processing method: accurately weigh 0.5000g gelatin sample, placed in 100mL PTFE digestion In the tank (stainless steel cover), add 5mL HNO3, 1mL H2O2, place the digestion tank in the oven, and react with high pressure at 130 °C for 3.5 hours. Until the sample is completely digested, a yellow clear solution appears, then remove the Teflon tank and place it. The low temperature electric heating plate is heated to catch acid, cooled and transferred to a 25 mL plastic volumetric flask, and the volume is to be tested. The same method is used to digest 9 samples as parallel test, and the same digestion method is used to make the sample blank. 1.4 Temperature program And the working curve instrument is calibrated by the standard curve method, and the concentration of the chromium standard solution is 2ng/mL, 5ng/mL, 8ng/mL respectively; the volume is adjusted to the scale with ultrapure water. The standard sample is tested according to Table 1. Take 20μL standard sample and 5μL ammonium dihydrogen phosphate separately, and draw a standard curve. 1.5 On the machine test, take 20μL sample and 5μL ammonium dihydrogen phosphate into the graphite tube. 1 The temperature program is used to test the absorbance of the sample, calculate the chromium content in the sample, and observe the precision of the same sample. 2. Results and discussion 2.1 Interference and elimination of various physical interferences and background interferences in the gelatin digestion solution, directly with atomic absorption The content of the test will be too high or too low. In this experiment, the background of the xenon lamp is used to remove the background interference, and the matrix modifier is used to improve the sensitivity, ensuring the accuracy of the test and the reproducibility of the results. 2.2 Test results During sample analysis Parallel tests were carried out on 9 groups of samples, and the contents of chromium in gelatin were measured: 3.21, 3.43, 3.15, 3.19, 3.40, 3.16, 3.37, 3.22, 3.24 μg/g. The digestion method is convenient, fast, and the test results are reproducible, and is suitable for routine analysis. Key words: atomic absorption spectrometer; chromium in gelatin; aesthetic instrument ; AA1800

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