邻二氮菲分光光度法测定稻米中的植酸含量

Determination of phytic acid content in rice by 1,10-phenanthroline spectrophotometry

建立了一种邻二氮菲分光光度法测定稻米植酸含量的方法:加入过量Fe^(3+)与植酸生成4∶1PA(Fe)4沉淀,再利用盐酸羟胺将剩余Fe^(3+)还原为Fe^(2+),以邻二氮菲为显色剂,采用分光光度法定量检测Fe^(2+),从而实现对稻米植酸含量的检测。对测定体系的pH和反应时间进行优化,分析无机磷酸对植酸含量测定的影响,验证方法的重复性和精确度。结果表明:在溶液p H为2.5、反应时间为30 min条件下,可准确测定的植酸浓度为6.7×10^(–7)~2.5×10^(–5)mol/L,低浓度和高浓度植酸测定工作曲线的R2均大于0.99;无机磷酸浓度低于2.0×10^(–5)mol/L时,游离的无机磷酸对植酸检测无影响;对6.7×10^(–7)~2.5×10^(–5)mol/L的标准样品进行5次平行试验,回收率为93.30%~104.67%,RSD为1.25%~7.34%。利用该方法测定的黄华占、金穗408、Kitaake、日本晴等4个品种的稻米植酸含量分别为5.42、4.72、6.40、5.68 mg/g,RSD为1.23%~7.60%。

In this study,a 1,10-phenanthroline spectrophotometry for the determination of phytic acid content in rice was established.The protocol included three steps,first add excess Fe 3+and phytic acid to form 4∶1 PA(Fe)4 precipitation,then use hydroxylamine hydrochloride to reduce the remaining Fe 3+to Fe^(2+),after that use 1,10-phenanthroline as a color developer to quantitatively detect Fe^(2+)by spectrophotometry,and finish the detection of phytic acid content in rice.The pH and reaction time of the determination system was optimized,and analyze the effect of inorganic phosphoric acid on the determination of phytic acid content,the reproducibility and accuracy of the method were verified.The results showed that the phytic acid concentration could be accurately determined in the range of 6.7×10^(-7)-2.5×10^(-5) mol/L under the pH 2.5 and reaction time was 30 min,and the R^(2) of the working curves for the determination of phytic acid at low and high concentrations were greater than 0.99.The free inorganic phosphate did not affect the detection of phytic acid when the inorganic phosphate concentration was lower than 2.0×10^(-5) mol/L.The recoveries were 93.30%-104.67%and the RSD of 1.25%-7.34%for five parallel tests on standard samples of 6.7×10^(-7)-2.5×10^(-5) mol/L.The phytic acid contents of the rice of four varieties,including Huanghuazhan,Jinsuo408,Kitaake and Nipponbare,determined by this method were 5.42,4.72,6.40,5.68 mg/g,the RSD were 1.23%to 7.60%.