小麦粉及其改良剂中痕量溴酸钾测定的甲酚红褪色分光光度法

在盐酸介质中,依据溴酸根离子氧化甲酚红褪色的原理提出了测定小麦粉及小麦粉品质改良剂中溴酸根离子的新方法。研究了各种因素如酸度、甲酚红的用浓度和用量、反应时间和温度等对测定的影响。结果表明,最优化的试验条件为最大吸收波长518 nm0,.6 mol/L盐酸1,.0 mL 1×10-4 mol/L甲酚红,85℃水浴条件下加热5 min。在优化的试验条件下,溴酸钾含量在3.0～10.0μg/mL之间存在线性关系,线性方程为ΔA=0.049 8C-0.151 4(C:μg/10 mL,相关系数0.999 6),检出限为0.02μg/g(取样量5 g),摩尔吸光系数为ε=1.1×105 L.mol-1.cm-1,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%～108%,相对标准偏差RSD<5%,能够满足检测需求。

Study on Spectrophotometric Determination of Trace Bromate Potassium by Oxidation-Decoloration of o-Cresolsulfonephthalein

A new Spectrophotometric method for determination of trace bromate in wheat flour proposed on oxidation of o-Cresolsulfonephthalein-hydrochloric acid system.The effects of some important factors,such as acidity,the concentration and the volume of o-Cresolsulfonephthalein,the reaction time and temperature were investigated to acquire the optimum condition.The result showed that the optimum condition was as followed the max-imum absorption peak is located at 518 nm,0.6 mol/L hydrochloric acid,1.0 mL 1.00×10-4 mol/L o-Cresolsulfonephthalein,the temperature was 85 ℃ and the reaction time was 5 min.Beer′s law is obeyed over the range of bromate potassium is 3～10 μg/10 mL.The regression equation is ΔA=0.0498C-0.1514(C: μg/10 mL)with the correlation coefficient of 0.9996.The detection limit was 0.02 μg/g with a molar absorptivity of 1.1×105 L·mol-1·cm-1.The method was used in the determination of trace bromate in wheat flour with satisfactory results.The recoveries of sample was in the range of 93%～108% and the relative standard deviation was below 5%.