苯酚红褪色分光光度法测定小麦粉中的痕量溴酸钾

对苯酚红褪色分光光度法测定小麦粉中痕量溴酸钾进行了研究。实验考察了各种因素如酸度、苯酚红的浓度和用量、反应时间和温度等对测定的影响。结果表明,在最优化的实验条件下(最大吸收波长为504nm,0.5mol/L盐酸,1.00mL 1.00×10-4mol/L苯酚红,85℃水浴条件下加热10min),溴酸钾在0—0.45μg/mL范围内符合比耳定律,线性回归方程为ΔA=0.6094C-0.0013(C:μg/mL,相关系数r=0.9991),摩尔吸光系数ε=3.6×106L.mol-1.cm-1,检出限为0.01μg/g(取样量5g)。将该法用于小麦粉中痕量溴酸钾的测定,样品加标回收率在93%—103%,相对标准偏差RSD<5%,结果满意。

Determination of Trace Potassium Bromate in Wheat Flour by Oxidation-Decolration Spectrophotometry of Phenol Red

A new spectrophotometric method for determination of trace potassium bromate in wheat flour was proposed with oxidation-decolration of phenol red.The effects of some important factors,such as acidity,the concentration and the volume of phenol red,the reaction time and temperature on the determination were investigated.The results showed that the optimum conditions were as followes:the maximum absorption peak of 504nm,0.5mol/L hydrochloric acid,phenol red concentration of 1.00×10-4mol/L for 1.00mL,the temperature of 85℃ and the reaction time of 10min.Beer’s law was obeyed in the range of 0—0.45μg/mL for potassium bromate.The regression equation was ΔA=0.6094C-0.0013(C:μg/mL)with the correlation coefficient of 0.9991.The detection limit for the amount sample of 5g was 0.01μg/g with the molar absorptivity coefficient of 3.6×106L·mol-1·cm-1.The method was used in the determination of trace potassium bromate in wheat flour with satisfactory results.The recovery of sample was in the range of 93%—103%,and the relative standard deviation was below 5%.