Development of a green liquid-liquid microextraction method using a home-made tablet disperser performed in a narrow-bore tube for trace analysis of Cd (II) and Pb (II) in aqueous samples

Heavy metal pollution is and will be a public health problem. Lead and cadmium, which produces several diseases, is one of the most important and widely distributed pollutants in the environment [1]. Dispersive liquid-liquid microextraction (DLLME) is a miniaturized sample pretreatment technique that uses microliter volumes of the extraction solvent[2]. Operation simplicity, rapidity, low sample volume, low cost and high enrichment factor are some of the DLLME advantages. Despite its merits, however, the use of a dispersersolvent at mL-level is a noticeable issue that increases solventconsumption and solubility of the analytes in aqueous solution andhence reduces partition coefficients of polar analytes into theextraction solvent. Therefore during the past few years othermicroextraction approaches were reported [3,4].In this work, we use effervescent tablets for disperse of organic phase into the aqueous phase. In other word dispersion of organic phase into the aqua phase via reaction of effervescent tablet with water that result produced gas bubbles is done. For the first time in-situ gas procedure was developed for the extraction and preconcentration of Pb(II) and Cd(II) from water samples. In this method, an inorganic acid and sodium bicarbonate are used to make a tablet disperser. Then µL-level of as an extraction solvent (toluene) is added to the tablet, and it was released into the narrow-bore tube containing sample and complexing agent. 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 proposed method made possible the determination of analytes in the range of 2-300µg L-1 with good linearity and favorable repeatability (relative standard deviation 5% for both intra-day, n = 6, and inter-day, n = 4, at a concentration of 40µg L-1 of Pb and 5 µg L-1 of Cd). Moreover, detection limits and enrichment factors of the analytes ranged from 0.7-10µg L-1and 135 to 140, respectively. Recoveries (85-102%, obtained at three fortification levels) confirmed the usefulness of the method for analysis of the analytes in environmental water and fruit juices. The method was shown to be fast, reliable, and environmentally friendly with low organic solvent consumption compared to conventional dispersive liquid-liquid microextraction.