Selective Preconcentration of Ultra Trace Mercury(II) in Aqueous Samples Using Membrane Disks Modified by Dithizone and Its Direct Spectrophotometric Determination

Abstract

A new simple and reliable method for rapid and selective extraction of mercury(II) in aqueous solution using octadecyl-bonded silica membrane disks modified with dithizone is presented. A simple modified spectrophotometric method was developed for direct determination of mercury(II) after elution of dithizonate complex from the membrane disk. Extraction efficiency and the influences of sample matrix, optimum amount of ligand, type and minimum amount of organic eluent, flow rates and type, and amount of alkaline stripping solution for free dithizone, were evaluated. The limit of detection of the proposed method is 0.03 ng/mL. The maximum capacity of the membrane disks modified with 2 mg of dithizone was found to be 397 ± 72 μg of mercury(II). Most of the cations and anions have no interfering effect on the extraction and determination of mercury. However, effects of some interfering species such as Cu²⁺, Ni²⁺ and Bi³⁺ were decreased or eliminated using different methods. The method was successfully applied to the recovery and determination of mercury(II) in synthetic and civic-waste water samples.