Liquid-phase microextraction based on the solidification of a floating organic microdrop for trace analysis of BTEX in the aqueous sample

Background: Benzene, toluene, ethylbenzene and xylenes (BTEX) are a group of volatile aromatic compounds. The human exposure to these compounds can comprise serious health consequences. Due to the toxicological properties of BTEX, there is an interest in the chemical control and consequently analytical procedures to measure these compounds. The objective of the present study was to develop a novel liquid-phase microextraction (LPME) based on solidification of floating organic microdrop coupled with gas chromatography flame ionization detection for pre-concentration and determination of BTEX in the aqueous samples. Results: Microextraction efficiency factors, such as the effects of type and volume of extraction solvent, stirring rate, extraction time, temperature, and ionic strength, have been investigated and optimized: 15.0-μL 1-undecanol microdrop exposed for 15 min floated on the surface of a 10-mL water sample at 45°C, stirred at 1,200 rpm without adding salt. Under the selected conditions, a pre-concentration factor of 211 to 417, limit of detection of 0.07 to 0.18 μg L^−1 (S/N = 3), limit of quantification of 0.22 to 0.49 μg L^−1 (S/N = 10), and linearity range of 1.00 to 300 μg L−1 for benzene, 0.10 to 300 μg L−1 for toluene, 0.05 to 150 μg L^−1 for ethylbenzene, and 0.02 to 150 μg L^−1 for xylenes, with coefficient of determination (0.9979 r2 0.9992), were observed. Relative standard deviation (RSD %) for analysis of 2.0 μg L^−1 BTEX compounds in water samples was in the range of 0.9% to 6.4% (n = 5). The relative recovery of different water samples was higher than 79.8%. Conclusions: The LPME method is a simple, rapid, economic and environmentally friendly technique that can be applied to the trapping of BTEX compounds from aqueous samples.