Analysis of trace mercury in water by solid phase extraction using dithizone modified nanometer titanium dioxide and cold vapor atomic absorption spectrometry

A new method for analysis of trace mercury in water samples was developed, based on the combination of preconcentration/separation using dithizone-modified nanometer titanium dioxide (TiO₂) as a solid phase extractant and determination by cold vapor atomic adsorption spectrometry (CVAAS). Dithizone was dissolved with alcohol and loaded on the surface of nano-sized TiO₂ powders by stirring. The static adsorption behavior of Hg²⁺ on the dithizone-modified nanoparticles was investigated in detail. It was found that excellent adsorption ratio for Hg₂₊ could be obtained in the pH range of 7–8 with an oscillation time of 15 min, and a 5 mL of 3.5 mol·L^?1 HCl solution could quantitatively elute Hg₂₊ from nanometer TiO₂ powder. Common coexisting ions caused no obvious influence on the determination of mercury. The mechanisms for the adsorption and desorption were discussed. The detection limit (3σ) for Hg²⁺ was calculated to be 5 ng·L^?1. The proposed method was applied to the determination of Hg²⁺ in a mineral water sample and a Zhujiang River water sample. By the standard addition method, the average recoveries were found to be 94.4%–108.3% with RSD (n = 5) of 2.9%–3.5%.