A green photometric method for determination of mercuric ions in saline samples by a single-drop microextraction technique

Abstract

This study describes a rapid, simple and sensitive spectrophotometric method for determination of Hg(II) ions in saline samples by a single-drop microextraction (SDME) technique. The method is based on the extraction of dithizone (DTZ) complex of mercury(II) into an undecanol droplet which serves as the organic phase, and then the absorbance of the colored complex is measured at 490 nm by using a microvolume quartz cuvette. This procedure provides a simple, rapid, cost-efficient and, most of all, a green method for detecting mercuric ions by minimizing the organic solvent consumption. A variety of parameters affecting the signal, such as pH, DTZ concentration, sample and extraction solvent volume, extraction time and temperature and salt effects were optimized. Under optimized conditions the linear range was found between 3.2 × 10⁻⁸ and 5.0 × 10⁻⁷ mol L⁻¹ (6.4–100.8 μg L⁻¹) and the detection limit was calculated as 9.6 × 10⁻⁹ mol L⁻¹ (1.9 μg mL⁻¹) attained by a high enrichment factor of 203. The performance and accuracy of the method were compared with those of atomic fluorescence spectrometry. Validation of the proposed method was performed for determination of mercury in saline samples including sea water, mineral water, thermal spring water, and table and rock salt samples, which is difficult to analyze by conventional methods.