Sequential Injection Fluorescence Spectroscopy Determination of Carbaryl in Environmental Water

Based on the fact that β-cyclodextrin forms a subject-object complex in Na2HPO4-citric acid buffer solution of pH 5.0 with carbaryl by embracing carbaryl in its inner cavity resulting enhancement of the inherent fluorescence of carbaryl, and by incorporating sequential injection technique of sample introduction, a method of sequential injection fluorescence spectroscopy determination of carbaryl in environmental water samples was proposed. Optimum working conditions for the instrument were given as follows: ① mode of sample introduction: di-band; ② concn. of β-CD in the reaction mixture: 3.5 mmol·L-1; ③ vol. of sample solution: 240 μL; ④ vol. of buffer solution: 100 μL; ⑤ flow-rate of sample solution: 5.0 mL·min-1; ⑥ scanning rate: 12 000 nm·min-1; and ⑦ wavelengths of excitation: 280 nm, and of emission: 334 nm. Under the precribed conditions, linear relationship between values of relative fluorescence intensity and mass concentration of carbaryl was obtained in the range of 0.90-210 μg·L-1. Detection limits (3s) was found to be 0.3 μg·L-1. Samples of river, lake and tap water were analyzed by this method, and test for recovery was performed by addition of standard solution of carbaryl to these samples as matrixes, giving results of recovery in the range from 91.8% to 109%.