Simultaneous determination of six earthy-musty smelling compounds in water by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry

A simple, rapid, sensitive and highly efficient method for the simultaneous determination of six earthy-musty smelling compounds, 2-isopropyl-3-methoxypyrazine, 2-isobutyl-3-methoxypyrazine, 2-methylisoborneol, 2,4,6-trichloroanisole, 2,3,6-trichloroanisole, and geosmin, in water samples was developed, using headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS). Experimental variables such as type of SPME fiber used, desorption temperature, desorption time, sample pH, salt concentration, extraction temperature, stirring speed, and extraction time were optimized. The results obtained showed that use of a polydimethylsiloxane/divinylbenzene/carboxen fiber gave a good extraction performance in terms of sensitivity and reproducibility. HS-SPME was carried out using a 20 mL water sample, with addition of 6 g of NaCl, stirring at 1000 rpm and at 70 degrees C for 30 min to pre-concentrate the target analytes. After that, the fiber was desorbed at 250 degrees C for 4 min and analysed by GC-MS. Under optimal conditions, the earthy-musty smelling compounds exhibited good linearity (R > 0.986) over the concentration range of 2.5-250 ng L-1. The repeatability and reproducibility of the method were less than 6.5% and 9.2%, respectively. The limit of detection and limit of quantification values were less than 1.0 ng L-1 and 2.5 ng L-1, respectively. The analyte recoveries for different water samples such as tap, pond, river and wastewater spiked at different concentrations were between 92.8 and 114.1%.