DISPOSITIVO PARA EXTRAÇÃO LÍQUIDO-LÍQUIDO EM SISTEMAS DE ANÁLISES EM FLUXO

Abstract

AbstractA device comprising a lab-made chamber with mechanical stirring and computer-controlled solenoid valves is proposed for the mechanization of liquid-liquid extractions. The performance was demonstrated by the extraction of ethanol from biodiesel as a model of the extraction of analytes from organic immiscible samples to an aqueous medium. The volumes of the sample and extractant were precisely defined by the flow-rates and switching times of the valves, while the mechanic stirring increased interaction between the phases. Stirring was stopped for phase separation, and a precise time-control also allowed a successful phase separation (i.e., the absence of the organic phase in the aqueous extract). In the model system, a linear response between the analytical response and the number of extractions was observed, indicating the potential for analyte preconcentration in the extract. The efficiency and reproducibility of the extractions were demonstrated by recoveries of ethanol spiked to biodiesel samples within 96% and 100% with coefficients of variation lower than 3.0%.

Keywords

• liquid-liquid extraction
• pre-concentration
• flow analysis