Ultrasound-assisted dispersive micro solid-phase extraction with nano-TiO₂ as adsorbent for the determination of...

The combination of ultrasound-assisted dispersive micro solid-phase extraction (USA DMSPE), with the use of TiO₂ nanoparticles (NPs) as adsorbent, with cold vapor atomic absorption spectrometry (CV AAS) is proposed for preconcentration and determination of mercury species (Hg_total, Hg²⁺ and CH₃Hg⁺) in biological, geological and water samples. The experimental parameters including the amount of TiO₂ NPs, pH of sample solution, ultrasonication and centrifugation time, TiO₂ slurry solution preparation before injection to CV AAS were investigated. Effective preconcentration of trace mercury with 10mg of TiO₂ was achieved in pH 7.5. After extraction, adsorbent with analytes was mixed with 500μL of 1molL^-1 HNO₃ to prepare slurry solution. The concentration limit of detection was 0.004ngmL^-1 for Hg²⁺. The achieved preconcentration factor was 35. The relative standard deviations (RSDs, %) for mercury species in real samples were 4-20%. The accuracy of this method was evaluated by analyses of certified reference materials: DOLT-2 (Dogfish Liver), IAEA-085 (Human hair), SRM 2709 (San Joaquin Soil), SRM 2711 (Montana Soil) and SRM 2704 (Buffalo River Sediment). The measured mercury species contents in reference materials were in satisfactory agreement with the added amounts (according to the t-test for a 95% confidence level). The presented method has been successfully applied for the determination of mercury species in real water samples (lake and river water).