HG-AFS Determination of Arsenic in Tea

HG-AFS was applied to the determination of arsenic in tea. Sample was digested with mixed acid of HNO3-HClO4(4+1). Hydride of As(Ⅲ) were generated from HCl (6+94) solution by using solution of 30 g·L-1 KBH4 in 5 g·L-1 KOH solution as reducing reagent. Flow-rate of 400 mL·min-1 for the carrier gas was taken in the analysis. Mixed solution of thiourea and ascorbic acid was added to the sample solution as pre-reductant. An aliquot of 1.2 mL of the sample solution was introduced and operated under the prescribed working condition of the instrument. Linear relationship between the fluorescence intensity and mass concentration of As was found in the range of 0.20-100 μg·L-1, with detection limit (3s/k) of 0.030 μg·L-1. The proposed method was applied to the analysis of sample solutions extracted from 3 varieties of tea, giving values of recovery ranged from 97.7% to 101.5%.