Determination of 5 Heavy Metals in Seawater by Atomic Absorption Spectrometry with Solid-phase Extraction of Hydrophobic Chelate

Abstract

The concentration and distribution of heavy metals in seawater are controlled by biogeochemical processes in the ocean. It is difficult to analyze accurately the concentrations of heavy metals in seawater due to the high salinity of seawater and low concentrations of heavy metals. Separation and preconcentration processes are needed. Conventional pretreatment methods include solvent extraction and coprecipitation. During solvent extraction, large volumes of seawater samples and organic solvents are used, complicating the procedure and endangering the environment and operator. The coprecipitation method can readily cause contamination of the analytes. In this study, the concentrations of 5 heavy metals, Cd, Cu, Ni, Pb and Zn in seawater were determined by Atomic Absorption Spectrometry after solid phase extraction of hydrophobic chelate with ammonium pyrrolidine dithiocarbamate and sodium diethyldithiocarbmate as chelating agents. The results show that there is a good correlation (R>0.999) between the absorbance and concentration of Cd, Cu, Ni, Pb and Zn. The linear ranges of the working curve for Cd and Zn were 0-4 μg/L and 0-100 μg/L, respectively, whereas the linear ranges for Pb, Cu, and Ni were 0-40 μg/L. The detection limits (μg/L) of Cd, Zn, Pb, Cu and Ni were 0.02, 2.6, 0.06, 0.18 and 0.3, respectively. The precision and recovery were less than 5% and 93.8%-104%, respectively. This method utilizes the hydrophobic interaction of solid phase extraction technology to realize the green sample pretreatment of seawater analysis.

Keywords

• seawater
• heavy metals
• solid phase extraction
• green separation technique
• dithiocarbamate
• atomic absorption spectrometry