Cloud-point extraction for the determination of Cd, Pb and Pd in blood by electrothermal atomic absorption spectrometry, using Ir or Ru as permanent modifiers

Abstract

The phase-separation phenomenon of nonionic surfactants occurring in aqueous solution was used to perform the extraction of Cd, Pb and Pd from digested blood samples. After complexation with O,O-diethyldithiophosphate (DDTP) in hydrochloric acid medium, the analytes are quantitatively extracted to the phase rich in the nonionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) after centrifugation. 0.1 mol L⁻¹ HNO₃ in methanol was added to the surfactant-rich phase prior to its analysis by electrothermal atomic absorption spectrometry (ETAAS). The adopted concentrations for DDTP, Triton X-114 and hydrochloric acid were all optimized, and the performance of 500 µg of either iridium or ruthenium as a permanent modifier was evaluated for the determination of Cd and Pb. No modifier was required for the Pd determinations. Detection limits (3σ_B) of 0.02 µg L⁻¹, 0.08 µg L⁻¹ and 0.014 µg L⁻¹, along with enrichment factors of 71, 34 and 100 for Cd, Pb and Pd, respectively, were achieved. The proposed procedure was applied to the analysis of two certified blood reference samples (lyophilized bovine blood and reconstituted human blood) after microwave-assisted digestion in a mixture of H₂O₂ and HNO₃. Comparison with certified values and recovery tests were performed to validate the methodology; good accuracy was obtained within the 95% confidence interval in both cases.