流动注射分光光度法测定水中痕量正磷酸盐

DETERMINATION OF TRACE PHOSPHATE IN WATER BY FLOW INJECTION SPECTROPHOTOMETRY

在一定酸度条件下，甲基绿与磷钼杂多酸在水相所形成的离子缔和物于６６５ｎｍ处有一最大吸收峰，而试剂空白的最大吸收在６３０ｎｍ左右．基于这一事实，笔者提出了直接测定痕量正磷酸根的流动注射分光光度法，天然水中常见离子不干扰痕量磷的测定，工作曲线的线性范围为０～５００μｇ·Ｌ－１（以磷计），检测下限可达１７μｇ·Ｌ－１，以１２０ｈ－１采样频率对水样进行测定，回收率为９２８％～１０７０％，相对标准偏差为０６１％～４６％．

A procedure for the flow injection spectrophotometric determination of trace phosphate is described.It involves the ion-associated complex formation of phospha-molybdoniobic acid with methyl blue,and measuring the absorbance at 665 nm.The optical condition was selected experimentally.The linear range of the method is from 0 to 500 μg.L -1 and the detection limit is 1.7 μg.L -1 .The method has been successfully applied to the determination of trace phosphate in nature water samples and interference ions has not been found in the samples.The recoveries and relative standard derivations of determining results for samples were 92.8%～107 0% and 0.61%～4.6%,respectively.The sampling frequency was 120 samplesh.