摘要：
Based on the catalytic effects of vanadium(V) on the discoloring reaction of methyl violet oxidized by potassium periodate and methyl violet in a medium of citric acid,a new method for the determination of vanadium(V) by catalytic kinetic spectrophotometry was proposed.The influence on the reaction medium,concentration of reactants,reaction temperature and reaction time were studied in the experiment to determine the linear range and detection limit,determinationof the apparent activation energy and apparent rate constant.Test samples were processed with wet digestion and microwave digestion to derermine by spectrophotometric method.The measuring wavelength was selected as 583nm In the citric acid medium,the vanadium had strong the catalytic role in the potassium periodate oxidation of methyl violet.The optimum experiment conditions for reaction was as follows,the 0.2 mol/L citric acid dosage of 3.0 mL,2×102 mol/L potassium periodate of 2.5 mL,1.0×10-4 mol/L methyl violet of 3.0 mL,reaction temperature of 90 °C and reaction time of 10 min.The method detection limit was 1.98×10-2 μg/mL,with the linear range of 0-1.0 μg/(25 mL),the catalytic reaction apparent activation energy of 10.097 kJ/mol and the apparent rate constant of 1.625×10 3 s 1.Handle sample with microwave digestion method has higher precision.Content of the experimentally measured samples did not exceed 120 mg/kg,samples of vanadium(V) content are qualified.%建立一种用分光光度法测定食品中钒(V)的方法,在柠檬酸介质中,根据高碘酸钾氧化甲基紫褪色反应测定食品中的钒(V).研究了反应介质、试剂用量、反应温度以及反应时间等因素的影响,同时测定表观活化能及表观速率常数,并绘制工作曲线,确定线性范围及检出限,采用湿法消化和微波消化分别处理红薯、黄瓜和雪莲果,利用分光光度法进行测定.实验结果表明,测定波长为583 nm,在柠檬酸介质中,钒对高碘酸钾氧化甲基紫具有强烈的催化作用.最佳实验条件:0.2 mol/L的柠檬酸3.0 mL,2×10-2 mol/L的高碘酸钾2.5 mL,1.0×10-4 mol/L的甲基紫3.0 mL,反应温度为90°C,反应时间为10 min,方法的检出限为1.98×10-2 μg/mL,线性范围为0-1.0 μg/(25 mL),催化反应的表观活化能为10.097 kJ/mol,表观速率常数为1.625×10-3s-1,利用微波消化法处理样品具有更高的精密度,实验测得的样品的含量均未超过120 mg/kg,样品中钒(V)含量均合格.
