Studies on contents of arsenic, selenium, mercury and bismuth in tea samples collected from different regions by atomic fluorescence spectrometry

After microwave or wet decomposition, the contents of arsenic, selenium, mercury and bismuth in twenty-one Chinese tea samples and five Japanese tea samples were determined by atomic fluorescence spectrometry, and plant standard reference materials were used to verify the accuracy and the precision of the analytical method. Moreover, the contents of these four elements were also determined in different parts of tea sapling sampled from the suburbs of Suzhou, a place famous for its Chinese tea biluochun. It was shown that microwave decomposition is indispensable for getting good results of mercury contents in tea samples by AFS. Compared with those in Japanese tea samples, the contents of arsenic, selenium, mercury and bismuth in Chinese tea samples are significantly high, but the Chinese tea sample produced in Hunan province has the lowest bismuth content. Arsenic, selenium and mercury are mainly present. in the bark, the root and the old leaves of tea sapling, nevertheless, the bismuth contents in the root and the bark-deprived trunk are so low that they can not be determined accurately. From this study, a preliminary conclusion can be drawn that tea is not a selenium-accumulating plant and the great majority of selenium in Chinese tea samples originates from the dry and wet deposition of atmospheric aerosols.