Column solid phase extraction as preconcentration method for trace element determination in oxalic acid by atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry

Column solid phase extraction using solid sorbent [Foam-Pap - hexamethyleneammonium hexamethylenedithiocarbamate (HMDC) immobilized on polyurethane (PU) foam mixed with methyltrioctylammonium chloride (MTOAC) immobilized on filter paper as well as the solid sorbent PU-HMDC-MTOAC mixture of the above ligands immobilized on polyurethane foam only] was applied to the preconcentration of traces of Cd, Co, Cu, Hg, Ni and Pb in analytical-reagent grade oxalic acid prior to their measurements by atomic absorption spectrometry (AAS) or inductively coupled plasma atomic emission spectrometry (ICP-AES). A disposable syringe served as a preconcentration column. Recoveries of sorption of the analytes were higher than 97%. For AAS determinations the solid chelate forming sorbents (HMDC and MTOAC) were completely dissolved in isobutyl methyl ketone (IBMK). The sorption on Foam-Pap sorbent combined with electrothermal AAS (ETAAS) allows the determination of 0.1 ng g−1 Cd, 0.3 ng g−1 Pb, 1 ng g−1 Ni, 2 ng g−1 Co and Cu, and 0.1 μg g−1 Hg. For ICP-AES measurements a quantitative elution was obtained with 4 mol 1−1 HNO3 for Cd, Cu, Ni and Pb, permitting the determination of 0.05 μg g−1 Cd, 0.1 μg g−1 Cu, 0.2 μg g−1 Ni and 1.0 μg g−1 Pb. The PU-HMDC-MTOAC sorbent permits the quantitative preconcentration of Cd, Cu, Fe, Hg and Pb. The combination of sorption on PU-HMDC-MTOAC sorbent with subsequent ETAAS determination allows the determination of 0.3 ng g−1 Pb, 0.4 ng g−1 Cd, 2 ng g−1 Cu and Fe, and 0.1 μg g−1 Hg.