Preliminary investigation and analysis on tea selenium content in Guangdong tea area

This paper applied hydride atomic-fluorescence to determine the Selenium content in tea, and determined the optimal conditions by testing digestion reagent mixed ratio, medium acidity and potassium borohydride -potassium hydroxide concentration. Selenium content of 35 tea samples taken from Guangdong tea area was analyzed to investigate preliminarily tea selenium levels and feasibility about developping se-enriched tea in Guangdong province. The results showed that mixed ratio of acid HNO3 and HClO4 of 4-1, hydrochloric acid concentration of 6.0 mol/L, potassium borohydride and potassium hydroxide concentration of 15.0 g/L and 2.0 g/L respectively were the optimal conditions to determine selenium content in tea. All the 35 tea samples contained selenium, selenium content of 13 tea samples was 0.039~0.097 mg/kg, accounting for 37.14%; selenium content of 20 tea samples was 0.100 ~0.197 mg/kg, accounting for 57.14% , selenium content of two tea samples was 0.229 mg/kg, 0.320 mg/kg, approached or reached enriched tea standard(required selenium content0.25 mg/kg). Oolong tea samples average selenium content was the highest, followed by green tea sample, black tea sample was minimum, which may be related with tea variety and processing technology.