Reversed-phase dispersive liquid-liquid microextraction for elemental analysis in gasoline by inductively coupled plasma optical emission spectrometry

In this work a green and fast sample preparation method based on reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) was developed for the separation and preconcentration of several elements (i.e., Ag, As, Ba, Cd, Cr, Cu, Hg, Mn, Mo, Ni, Pb, S, Se, Sn and V) in gasoline samples before Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) determination. The extraction procedure was carried out in a reverse mode, since a small volume of aqueous phase (i.e., HCl 8M) is used to extract a relatively high volume of organic phase (i.e., gasoline sample). Unlike conventional DLLME, in the RP-DLLME the analytes were extracted from the organic phase into the aqueous phase. The experimental conditions for the microextraction procedure were: 5 g of sample, HCl 8M as extractant phase, mechanically stirred by vortex as dispersion system, 115 µL of extractant volume, and 2 min for extraction and 5 min centrifugation time. Under optimized extraction conditions the enrichment factor ranged between 3-53, and limits of detection ranged between 0.02 and 50 µg kg-1. The proposed analytical method was validated and successfully used to analyze three gasoline samples. All gasoline samples were spiked at 100 μg kg-1 for all analytes, except sulfur (in this case at 1000 μg kg-1), obtaining recovery and RSD values within the range of 88-109% and 2-9%, respectively.