Introducing Organic Gas Steam-Liquid Extraction as a New Preconcentration Method for Benzene, Toluene, Ethylbenzene and Xylene Determination in Water Samples by Gas Chromatography-Flame Ionization Detection

In this study, for the first time, the organic gas steam-liquid extraction by a special hand-made cell was used as a simple and inexpensive preconcentration technique for the determination of benzene, toluene, ethylbenzene and xylene in aqueous samples by gas chromatography-flame ionization detection. In this technique, the organic solvent vapor produced in the evaporator unit is introduced into the aqueous sample by using nitrogen as a carrier gas to extract target analytes. By entering the vapor bubbles of the organic solvent into the aqueous sample, the organic solvent dissolves in water and the organic solvent concentration in water reaches supersaturation. At this time, equilibrium occurs between the dissolved organic solvent and the insoluble organic solvent, and it is collected in the conical part of the cell. Using a microliter syringe, a certain volume of the collected organic solvent is injected into the gas chromatograph. Face central composite design was used to evaluate the effect of various factors including organic solvent volume, ionic strength, evaporating gas flow rate and heated chamber temperature. Under the optimized conditions, the detection limit, relative standard deviation and linear dynamic range of the method were 10 µg/L, 5.3–8.7% ( n = 4) and 50–5000 µg/L, respectively. The proposed method was successfully applied to the determination of benzene, toluene, ethylbenzene and xylene in real samples.