Abstract :
A new approach for developing a cloud point extraction-electrothermal atomic absorption spectrometry has been described and used for determination of arsenic. The method is based on phase separation phenomenon of non-ionic surfactants in aqueous solutions. After reaction of As(V) with molybdate towards a yellow heteropoly acid complex in sulfuric acid medium and increasing the temperature to 55 (degree)C, analytes are quantitatively extracted to the non-ionic surfactant-rich phase (Triton X-114) after centrifugation. To decrease the viscosity of the extract and to allow its pipetting by the autosampler, 100 (mu)l methanol was added to the surfactant-rich phase. An amount of 20 (mu)l of this solution plus 10 (mu)l of 0.1% m/v Pd(NO3)2 were injected into the graphite tube and the analyte determined by electrothermal atomic absorption spectrometry. Total inorganic arsenic(III, V) was extracted similarly after oxidation of As(III) to As(V) with KMnO4. As(III) was calculated by difference. After optimization of the extraction condition and the instrumental parameters, a detection limit (3(sigma)B) of 0.01 (mu)g l^-1 with enrichment factor of 52.5 was achieved for only 10 ml of sample. The analytical curve was linear in the concentration range of 0.02-0.35 (mu)g l^-1. Relative standard deviations were lower than 5%. The method was successfully applied to the determination of As(III) and As(V) in tap water and total arsenic in biological samples (hair and nail).
