Determination of noble metals in biological samples by electrothermal vaporization inductively coupled plasma mass spectrometry, following cloud point extraction

A simple separation procedure for noble metals based on cloud point extract ion is proposed. The analyte ions in aqueous acidic solution, obtained by t he acid digestion of the samples, were complexed with O,O-diethyldithiophos phate and Triton X-114 was added as a non-ionic surfactant. By increasing t he temperature up to the cloud point, a phase separation occurs, resulting in an aqueous phase and a surfactant-rich phase containing most of the anal ytes that were complexed. The metals in the surfactant-rich phase were dete rmined by electrothermal vaporization inductively coupled plasma mass spect rometry. The extraction conditions as well as the instrumental parameters w ere optimized. Enrichment factors ranging from 7 (Rh) to 60 (Pt) and limits of detection from 0.6 (Pt) to 3.0 ng l(-1) (Rh) were obtained in the diges ted samples. The extraction was not efficient for Ir. Among the reference m aterials analyzed in this work, only one (SRM 2670, urine) presented recomm ended values for Au and Pt. Due to the non-availability of adequate CRMs, a ccuracy was assessed by spiking known analyte amounts to the acid digests. Recoveries close to 100% were observed for all the studied elements but Ru. Poor agreement between found and recommended values was observed for non-d igested urine sample, probably due to the carrier effect of co-extracted re sidual matrix components. However, good agreement was reached after urine a cid mineralization. (C) 2001 Elsevier Science B.V. All rights reserved.