Factorial design optimization of dispersive liquid–liquid microextraction for analysis of metals in natural and drinking waters

Abstract

In this work, a dispersive liquid–liquid microextraction method combined with inductively coupled plasma optical emission spectrometry was developed to extract and pre-concentrate the trace metals cadmium and lead. Variables such as extracting solvent, dispersive solvent and chelating agent were studied using a univariate design. On the other hand, parameters such as pH, volume of the extracting solvent, volume of the dispersive solvent and concentration of the chelating agent were optimized using a factorial design 24. Doehlert design was used to improve the conditions established in the factorial design. The optimized method consisted of chelating agent concentration of 0.05 % (w/v), 8000 µL of dispersive solvent (ethanol), 600 µL of extracting solvent (chlorobenzene) and a pH of 7.0. Using these conditions, it was obtained a limit of detection of 0.85 and 0.55 µg L-1, enrichment factors of 13.4 and 10 and relative standard deviation of 0.8 and 3.7 % (5 µg L-1, n = 3) for the metals Cd and Pb, respectively. The developed methodology was applied for the analysis of cadmium and lead in natural and drinking water samples.