Multi-element determination for green tea leaves and their extractants by ICP-AES with online concentration

A collection/concentration system controlled automatically by a lab-made program incorporated in ICP-AES was used to determine multi-elements in green tea leaves and their extracts into hot water. Twenty four elements (Cd, Ce, Co, Cu, Dy, Er, Eu, Gd, Ho, La, Lu, Nd, Ni, Pb, Pr, Sc, Sm, Tb, Th, Tm, V, Y, Tb and Zn) could be collected on a ME-3 chelating resin packed in a mini-column. This mini-column was installed in the selection valve on the collection/concentration system, which was connected on line to ICP-AES. Conditioning of the resin was carried out with a 1 mL portion of a 0.5 M ammonium acetate buffer solution (pH 5.5) at a flowing rate of 50 μL min^-1, collecting elements with 10 mL of the sample solution (pH 5.5) at a flowing rate of 70 μL min^-1, and washing with 0.5 mL of water. HNO₃ at 35 μL min^-1 Elution was done by passing through 2.5 mL of 2 M. The enrichment factors of elements were from 40 to 74, and the detection limits (LOD) were from 0.01 ppb to 0.20 ppb. The RSDs of 7 measurements with 0.5 ng Ml^-1 standard solution were between 2.9 and 8.9%. Tea leaves were digested by a microwave without hydrofluoric acid after predigesting and the digested solutions were measured directly by ICP-AES. The extracts from tea leaves in hot water could be measured with the proposed collection/concentration system.