Determination of trace elements in analytical-reagent grade sodium salts by atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry after preconcentration by column solid phase extraction

Abstract

Column solid phase extraction using solid ammonium hexahydroazepine-1-dithiocarboxylate (ammonium hexamethylenedithiocarbamate)(HMDC) mixed with polyurethane foam was applied to the preconcentration of trace amounts, of Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni and Pb from analytical-reagent grade sodium salts prior to their measurements by atomic absorption spectrometry (AAS) or inductively coupled plasma atomic emission spectrometry (ICP-AES). A 2 ml disposable syringe served as a preconcentration column. Except for Cr, recoveries of sorption of the elements tested were higher than 98% with absolute blanks ranging between 5 ng (Co) and 50 ng (Cu). For AAS determination of the preconcentrated analytes, the solid chelate forming sorbent (HMDC) was completely dissolved in isobutyl methyl ketone (IBMK). Electrothermal AAS allows the determination of 1 × 10^–7% Cd, 3 × 10^–7% Mn, 5 × 10^–7% Pb, 1 × 10^–6% Co, 2 × 10^–6% Ni, 4 × 10^–6% Fe and 1 × 10^–5% Cu. For ICP-AES measurements a quantitative elution was obtained with 4 mol l^–1 HNO₃ permitting the determination of 5 × 10^–6% Cd and Mn, 1 × 10^–5% Cu and Fe, 2 × 10^–5% Ni and 1 × 10^–4% Pb. The elution of Co and Hg from the sorbent with 4 mol l^–1 HNO₃ was incomplete.