FI/SI on-line solvent extraction/back extraction preconcentration coupled to direct injection nebulization inductively coupled plasma mass spectrometry for determination of copper and lead

An automated sequential injection on-line preconcentration procedure for determination of trace levels of copper and lead via solvent extraction/back extraction coupled to ICP-MS is described. In citrate buffer of pH 3, neutral complexes between the analytes and the chelating reagent, ammonium pyrrolidinedithiocarbamate ( APDC), are extracted into isobutyl methyl ketone (IBMK). The organic phase is separated from the aqueous one by means of a dual-conical gravitational phase separator, and stored in a PTFE holding coil. Afterwards, the organic phase is propelled and mixed with an aqueous back extractant of nitric acid containing Pd(II) ions as stripping agent, thereby facilitating a rapid metal exchange reaction with the APDC ligand and transfer of the analytes back into the aqueous phase. The aqueous phase is separated in a second dual-conical gravitational phase separator, and 30 m is entrapped in a sample loop, the content of which is subsequently introduced into the ICP-MS, via a direct injection high efficiency nebulizer (DIHEN), for quanti cation. Enrichment factors of 29.6 (Cu) and 23.3 (Pb), detection limits of 17 ng(-1) (Cu) and 11 ng(-1) (Pb), along with a sampling frequency of 13 h(-1) were obtained at a sample flow rate of 6.0 ml min(-1). The precisions (RSD) at the 0.2 mug l(-1) level were 4.4% (Cu) and 4.8% (Pb), respectively. The applicability of the procedure is demonstrated for the determination of copper and lead in three certified reference materials and a urine sample.