Determination of trace amounts of off-flavor compounds in drinking water by stir bar sorptive extraction and thermal desorption GC-MS

Abstract

A method for the determination of trace amounts of off-flavor compounds including 2-methylisoborneol, geosmin and 2,4,6-trichloroanisole in drinking water was developed using the stir bar sorptive extraction technique followed by thermal desorption-GC-MS analysis. The extraction conditions such as extraction mode, salt addition, extraction temperature, sample volume and extraction time were examined. Water samples (20, 40 and 60 ml) were extracted for 60–240 min at room temperature (25 °C) using stir bars with a length of 10 mm and coated with a 500 μm layer of polydimethylsiloxane. The extract was analyzed by thermal desorption-GC-MS in the selected ion monitoring mode. The method showed good linearity over the concentration range from 0.1 or 0.2 or 0.5 to 100 ng l⁻¹ for all the target analytes, and the correlation coefficients were greater than 0.9987. The detection limits ranged from 0.022 to 0.16 ng l⁻¹. The recoveries (89–109%) and precision (RSD: 0.80–3.7%) of the method were examined by analyzing raw water and tap water samples fortified at the 1 ng l⁻¹ level. The method was successfully applied to low-level samples (raw water and tap water).