荧光分光光度法测定乐果——以钙黄绿素-Pd^(2+)作为荧光探针

Fluorospectrophotometric Determination of Dimethoate with Calcein-Pd^(2+) as Fluorescence Probe

在pH 7.98磷酸盐缓冲溶液中,Pd2+与钙黄绿素形成物质的量比为1比1的配合物,导致荧光试剂钙黄绿素荧光强度猝灭。向上述溶液中加入乐果,乐果与Pd2+作用形成比钙黄绿素-Pd2+稳定性更强的配合物,而使钙黄绿素游离出来重现荧光,且荧光强度随乐果质量浓度在0.2~1.2 mg.L-1范围内增加而增大,据此建立了以钙黄绿素-Pd2+作为荧光探针法测定乐果的方法,以实样为基体用标准加入法按方法作回收试验,测得回收率在82%~108%之间。

In a phosphate buffer medium of pH 7. 98, a complex with mole ratio of 1 to 1, was formed by the reaction of Pd^2＋ with calcein, leading to fluorescence quenching of the reagent. Upon addition of dimethoate to the above solution, a more stable complex was formed by the reaction of dimethoate with Pd^2＋, and calcein was displaced from the calcein-Pd^2＋ complex, leading to resumption of its fluorescence. It was found that linear relationship between the magnitude of increase in fluorescence intensity and mass concentration of dimethoate was kept in the range of 0. 2-1.2 mg · L^-1 when measured at the wavelengths of 490 nm （λex） and 512 nm （λem）. Based on these facts, a sensitive method for fluorospectrophotometric determination of dimethoate was proposed with calcein-Pd^2＋ as fluorescence probe. Recovery of the method was tested by standard addition method, and the values of recovery obtained were ranged from 82% to 108%.