Determination of Organic Sulfur Contaminants Using Hollow Fibre-protected Liquid-phase Micro-extraction Coupled with Gas Chromatography

A simple and solvent-minimized sample preparation technique based on hollow fibre-protected liquid-phase micro-extraction has been developed for extraction of fifteen organic sulphur compounds from aqueous samples. The analysis of the extracted them was performed by gas chromatography equipped with mass spectrometry and/or flame photometric detectors. 3.3 µL of organic solvent located in the lumen of hollow fibre was used to extract OSCs from an 8 mL of aqueous sample. Several parameters influencing extraction efficiency such as salt concentration, stirring speed, temperature, sample volume, organic phase volume and extraction time were studied and optimized using super-modified simplex method. Under optimized conditions, including extraction solvent (toluene) extraction time (15 min ), salt addition (4 % w/v), stirring rate (1200 rpm), sample volume (8 ml SV), organic solvent volume (3.3 µl) and extraction temperature (35oC), the limits of detection varied from 0.1 to 8.7 µg/L and 0.7 to 99.4 µg/L for GC-FPD and GC-MS, respectively. The calibration graphs were linear over three orders of magnitude for most of the studied OSCs. The relative standard deviations for inter- and intra-day analysis were in the range of 5 to 10%, and the relative recoveries of the analytes from the three different real water samples were more than 83%. The results were compared with those obtained using direct single drop micro-extraction and headspace single drop micro- methods. The proposed method is reliable and can be considered useful for routine monitoring of the organic sulphur compounds in surface water samples.