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 sulfur compounds (OSCs) from aqueous samples. The analysis of the extracted OSCs 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 8 ml of an 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 (35 °C), the limits of detection varied from 0.1 to 8.7 μg l-1 and 0.7 to 99.4 μg l-1 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 5-10%, and the relative recoveries of the analytes from 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 micromethods. The proposed method is reliable and can be considered useful for routine monitoring of the organic sulfur compounds in surface water samples.