Simultaneous temperature-assisted dispersive liquid–liquid microextraction of cobalt, copper, nickel and zinc ions from high-volume water samples and determination by graphite furnace atomic absorption spectrometry

Abstract

A rapid, efficient, and reliable sample preparation method based on temperature-assisted dispersive liquid–liquid microextraction was developed for simultaneous extraction of cobalt, copper, nickel, and zinc ions at a low level from high volume water samples. Sodium diethyldithiocarbamate was used as a chelating agent. In the proposed method, the temperature of a high-volume aqueous phase containing the analytes and chelating agent was adjusted at an elevated temperature and then a mixture of a dispersive solvent and extraction solvent was rapidly injected into it. After placing the tube in an ice water bath, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by graphite furnace atomic absorption spectrometry (GFAAS). Several variables possibly affecting the extraction efficiency, including the amount of the chelating agent, type and volume of the extraction and dispersive solvents, temperature, pH, salting out effect, and centrifugation rate and time, were investigated and optimized. Under optimum conditions, calibration graphs were linear in the range of 2.85–100 ng L⁻¹. The method resulted in low limits of detection and quantification within the ranges of 0.89–1.82 ng L⁻¹ and 2.85–5.20 ng L⁻¹, respectively. Enrichment factors were in the range of 671–715. Relative standard deviations obtained for six repeated experiments (15 ng L⁻¹) were less than 4%. The accuracy of the developed procedure was checked by analyzing NRCC-SLRS4 Riverine water, a certified reference material. Finally, the proposed method has been successfully applied for the simultaneous analysis of the selected analytes in environmental water samples.