Determination of trace lead by catalytic kinetic spectrophotometry based on fading of methyl green oxidized by potassium bromate
ZHANG Yue, LIU Bin*, YANG Huixi, DU Yanping, CHANG Wei
Xi'an Key Laboratory of Textile Chemical Engineering Auxiliaries, School of Environmental and Chemical Engineering, Xi'an Polytechnic University, Xi'an 710600, China
Abstract：In the medium of hydrochloric acid, the oxidant of potassium bromate could oxidize methyl green to fade and decrease its absorbance. Lead ions could catalyze the reaction. Based on this, a determination of trace lead was established by catalytic kinetic spectrophotometry based on the fading reaction of methyl green oxidized by potassium bromate. Two stoppered glass colorimetric tubes of the same specification were taken. One was added with 2.1 mL methyl green solution, 1.0 mL hydrochloric acid, 0.9 mL potassium bromate solution, and a certain amount of lead standard solution, the other was a blank control without lead solution. After reacting in a boiling water bath at 100 ℃ for 10 min, the absorbance of the catalytic system (with lead) and the non-catalytic reaction system (without lead) at the maximum wavelength of 631 nm were determined with an ultraviolet-visible spectrophotometer, and the difference in absorbance was calculated. The results showed that, the lead mass concentration within the range of 0.004-0.12 μg/mL had a good linear relationship with the difference in absorbance, and the correlation coefficient was r=0.999 7. The rate constant of the catalytic reaction was 3.5×10-1 s-1, the apparent activation energy was 11.99 kJ/mol; the limit of detection for the method was 2.8×10-3 μg/mL, and the limit of quantification was 9.5×10-3 μg/mL. The experimental method was applied to the determination of lead in domestic sewage and wastewater of printing and dyeing. The relative standard deviation (RSDs, n=6) of the results were 1.6%-3.6%. The results are basically consistent with atomic absorption spectrometry, and the recoveries were 95%-108%.
张悦, 刘斌, 杨荟茜, 杜燕萍, 常薇. 溴酸钾氧化甲基绿褪色催化动力学光度法测定痕量铅[J]. 冶金分析, 2021, 41(9): 91-95.
ZHANG Yue, LIU Bin, YANG Huixi, DU Yanping, CHANG Wei. Determination of trace lead by catalytic kinetic spectrophotometry based on fading of methyl green oxidized by potassium bromate. , 2021, 41(9): 91-95.
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