Determination of As, Cd, and Pb in epicuticular waxes of pine and spruce needles by ETAAS

Abstract

 Waxes were separated from needles by chloroform washing, drying and dissolving the residue in tetrahydrofuran (THF). Both a THF solution of the wax and an aqueous solution of the Pd-Mg matrix modifier were sampled directly into the graphite tube. The reaction conditions were optimised for the wax concentration of 45 mg ml^-1 in THF and the Pd:Mg ratio of 1:1 in the matrix modifier. The atomisation and charring temperatures for As, Cd and Pb were the same as those recommended for analysis of aqueous solutions except the charring temperature of Cd takes 200 °C lower. The characteristic masses for As (26 pg), Cd (0.5 pg) and pb (9 pg) are also comparable to published data. The parameters of calibration curves were identical for all three elements dissolved either in clear THF or in the wax solution. Elemental concentrations were found to range from 0.1 to 1.0 mg g^-1, increasing with needle age for As, Pb but not Cd.