In situ produced gas-based disperser liquid-liquid microextraction for extraction and preconcentration of cobalt, nickel and copper ions from aqueous samples followed by graphite furnace atomic absorption spectrometry determination

Prior to assess low concentration in a complex matrix, performing separation and preconcentration techniques are compulsory to eliminate or minimize matrix effects which leads to low detection limit and improved sensitivity of detection techniques towards metals. In conventional dispersive liquid-liquid microextraction (DLLME), an extraction solvent is dispersed into an aqueous sample solution with the aid of a disperser solvent [1]. The presence of relatively high volume of the disperser solvent (usually 1-2 mL for 5 mL aqueous sample) makes the aqueous phase relatively nonpolar and results in an increased solubility of the target lipophilic analytes into the aqueous sample solution leading to relatively low extraction efficiency [2].In this study, insitu produced gas-disperser liquid-liquid microextraction followed by graphite furnace atomic absorption spectrometry detection has been developed for the extraction and preconcentration of cobalt, nickel, and copper from aqueous samples. In the proposed method, initially a solid mixture of an inorganic acid and sodium bicarbonate is placed in the bottom of a conical and dried glass test tube. Then µL-level of 1,1,2,2-tetrachloroethane as an extraction solvent is added to the tube. An aqueous solution of the analytes containing sodium diethyldithiocarbamate (as a chelating agent) is transferred into the tube. The reaction between the acid and sodium bicarbonateis immediately occurred, and the produced gas leads to dispersion of the extraction solvent as tiny droplets into the sample and subsequent extraction of the analytes. The cloudy solution is centrifuged and the sedimented phase is analyzed by the analytical method.Under the optimum conditions the calibration curves were linear in the range of 20-300 ng L-1. Repeatability of the proposed method, expressed as relative standard deviation, ranged from 2.3-4.6% and 4.5-5.6% for intra- and inter-day (n=6, C=50 ng L-1) precisions, respectively. Moreover, the detection limits and enrichment factors of the selected analytes were obtained in the ranges of 6.2-12 ng L-1 and 139-150, respectively. The accuracy of the developed procedure was checked by analyzing NRCC-SLRS4 Riverine water as a certified reference material. Finally, the proposed method has been successfully applied for thesimultaneous analysis of the selected analytes in environmental water and fruit juicesamples.