Quantitative Analysis Of Different Valence Chromium And Ions In Rice

Cr（Ⅲ）is an essential element for human body and the Cr（Ⅵ）is a carcinogenic factor.While there are few studies on chromium in different valences and trace elements of rice at home and abroad.It is impossible to quantify the content of water-soluble Cr（Ⅲ）and Cr（Ⅵ）with higher physiological activity only by studying the total chromium content.The nutritional information of rice cannot be obtained comprehensively only by studying the main nutrients.In view of the above problems,this paper explores the quantitative analysis methods for the contents of chromium in different valences,anions and cations of rice.The effects of two pretreatment methods,dry ashing and high-pressure digestion,on the analysis results of total chromium in the rice detection process were explored.It was concluded that the high-pressure digestion method had higher stability and accuracy.The experiment used high-pressure digestion-graphite furnace atomic absorption spectrometry to determine the total chromium content of rice from 8different sources.The method had a good linear relationship,the relative standard deviation（RSD）was 3.28%,and the recovery rate was 95.98%.The paper selected rice with higher chromium content to provide raw materials for subsequent analysis experiments of water-soluble chromium in different valence states.The analytical method for quantifying the content of water-soluble Cr（Ⅲ）and Cr（Ⅵ）in rice by high performance liquid chromatography（HPLC）was study.Due to the small response value and low sensitivity of Cr（Ⅲ）by direct measurement.It conducted that a pre-column derivation experiment on Cr（Ⅲ）:Using 2,6-pyridine dicarboxylic acid（PDCA）as the derivative agent,derivatived at 130℃for 40 min to improve the detection sensitivity of Cr（Ⅲ）.Rice samples were prepared by ultrasonic-oscillation assisted leaching method in hot water.Under the analytical conditions,the chromatographic column was a C18 column,the mobile phase was a PDCA mixture,the detection wavelength was 320 nm,the flow rate was 1.2 m L/min and the column temperature was 30℃,the quantitative analysis of Cr（Ⅲ）and Cr（Ⅵ）had a good linear relationship.The detection limits were 0.0425 mg/kg and 1.0325 mg/kg,respectively.The recovery rates were ranged from 99.98%to 102.82%and from 96.14%to 100.38%,respectively.RSD were ranged from 0.84%to 1.01%and from 0.96%to 1.04%,respectively.This method can quantify the content of water-soluble Cr（Ⅲ）and Cr（Ⅵ）in rice accurately.Research on the analysis method of anion chromatography-conductivity detection method to quantify content of anions in rice in which optimize the chromatographic conditions so that the 10 anions can be separated completely and quantified accurately.The rice samples were prepared by ultrasonic-oscillation assisted leaching method in hot KOH solution.Under the analytical conditions,the chromatographic column was an anion exchange column,the eluent was 16 mmol/L KOH solution,the column temperature was 60℃and the flow rate was 1.0 m L/min,the quantitative analysis of the 10 anions had a good linear relationship.The detection limit were ranged from0.0063 to 0.0329 mg/kg,the RSD were lower than 2.01%,and the recovery rates were ranged from 92.52%to 106.39%.The analytical method can be directly applied to the detectionation of soluble inorganic anions F^-,Cl^-,NO₂^-,Br^-,NO₃^-,SO₄^2-,PO₄^3-,organic anions Ac^-,C₂O₄^2-and heavy metal Cr O₄^2-in rice samples.Establishment of cation chromatography-conductivity detection method to quantify cation content in rice.The rice samples were extracted by ultrasonic-oscillation-assisted methanesulfonic acid hot extraction.Under the analytical conditions,the chromatographic column was an cation exchange column,the eluent was 20 mmol/L methanesulfonic acid solution,the column temperature was 30℃and the flow rate was 1.0 m L/min,the quantitative analysis of Li⁺,Na⁺,NH₄⁺,K⁺,Mg²⁺,Ca²⁺had a good linear relationship.The detection limit were ranged from 0.0012 to0.0203 mg/kg,the recovery rates were ranged from 94.40%to 102.20%,RSD were lower than 1.68%.The method has good repeatability and high sensitivity,and it is suitable for quantitative analysis of cations content in rice samples.