Determination on Selenium Content in Tea by Microwave Digestion and Molecule Fluorescence Photometry

[Objective] The purpose was to discuss the optimum condition for determining the selenium content in tea by microwave digestion and molecule fluorescence photometry.[Method] The tea sample was digested by microwave digestion.The 4,5-benzo piaselenol with the strong fluorescence characteristic was prepared by reaction between the selenium(IV) in the tea and DAN(2,3-diaminonaphthalene) under acidic condition,and then the selenium content in the tea was detected by molecule fluorescence photometry and the microwave digestion condition was optimized.[Result] The condition for digesting the tea sample by microwave chemical reactor was follows: 5.0% sulfate at 5.0 ml was added into the sample for wetting and HNO3HClO4(41) 10.0 ml was added into it for digesting at 0.20 kW for 30 min.The optimum detecting contion was follows: pH of 1.5-2.0,dosage of EDTA-hydroxylamine hydrochloride mixed solution being 20.0 ml,dosage of 0.1% DAN being 5.0 ml,heating by the boiled water for 5 min,extracting by 6.0 ml cyclohexane and detecting the fluorescence intension under the excitation wavelength of 377 nm and the emission wavelength of 519 nm.There was a good linear relation with fluorescence intension when the selenium content was 1.0-7.0 μg,with R2 of 0.991 6 and the relative standard deviation(RSD) was 2.5%.[Conclusion] In comparison with the determination by the wetting digestion,the determination results of microwave digestion was reliable,simple and quick.