Sequential determination of gallium, indium, and thallium in environmental samples after preconcentration on halloysite nanotubes using ultrasound-assisted dispersive micro solid-phase extraction

Abstract

Ultrasound-assisted dispersive micro solid-phase extraction (USA DMSPE) with halloysite nanotubes (HNTs) as a solid sorbent was proposed for preconcentration of gallium, indium, and thallium. After extraction, the analytes were sequentially determined by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS). The experimental parameters including the pH of the sample solution, the amount of HNTs, and the ultrasonication time, as well as the main parameters of HR-CS GFAAS, were investigated. The concentration limits of detection were 0.02, 0.01, and 0.04 μg L⁻¹ for Ga, In, and Tl, respectively. The preconcentration factors achieved for Ga, In, and Tl were 33, 37 and 31, respectively. The relative standard deviations (RSDs) were 4%, 5% and 3% for Ga, In, and Tl, respectively. The accuracy of this method was validated by the analyses of TMDA-54.5 (a high level fortified sample for trace elements) and NIST SRM 2711 (Montana Soil) certified reference materials. The measured contents of elements in these reference materials were in satisfactory agreement with the certified values according to the t-test for a 95% confidence level. The proposed method has been successfully applied to the determination of gallium, indium, and thallium in soil and water samples (seawater, river water, and mine water).