Determination of volatile organic compounds in water using headspace knotted hollow fiber microextraction

An efficient and effective headspace microextraction technique named static headspace knotted hollow fiber microextraction (HS-K-HFME) has been developed for the determination of volatile organic compounds (VOCs) in water samples. The knot-shaped hollow fiber is filled with 25 μL of the extraction solvent. The excess solvent forms a large droplet (13 μL) and is held in the center of the knot. Even after 20 min of extraction time at high temperature (95 °C) without cooling, there was still enough volume of extraction solvent for gas chromatography-mass spectrometry (GC-MS) analysis, which extends the choice of solvents for headspace LPME. Moreover, the knot-shaped fiber has a larger extraction contact interface, which increases the rate of mass transfer between the headspace and extraction solvent film attached to the fiber, thus improving the extraction efficiency. The effects of extraction solvent, temperature, stirring rate, salt concentration and extraction time on extraction performance were optimized. The calibration curves exhibited coefficients of determination (R2) ranging from 0.9957 to 0.9999 and the limit of detection (LOD) ranged from 0.2 to 10 μg L−1. Relative standard deviations (RSDs) ranged from 4.5% to 11.6% for intraday measurements (n = 5). Interday (n = 15) values were between 2.2% and 12.9%. The relative recoveries (RRs) ranged from 90.3% to 106.0% for river water and 95.9% to 103.6% for wastewater.