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

Abstract

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 (TiO 2) 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 TiO 2 powders by stirring. The static adsorption behavior of Hg 2+ on the dithizone-modified nanoparticles was investigated in detail. It was found that excellent adsorption ratio for Hg 2+ 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 Hg 2+ from nanometer TiO 2 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 Hg 2+ was calculated to be 5 ng·L −1. The proposed method was applied to the determination of Hg 2+ 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%.