Determination of trace levels of taste and odor compounds in water by microextraction and gas chromatography ion trap detection mass spectrometry

A simple, easy-to-perform and sensitive method for routine analysis of trace taste- and odor-causing organic compounds in natural water is presented. The compounds investigated included geosmin, 2-methylisoborneol (MIB), C6C10 linear aldehydes, benzaldehyde, beta-cyclocitral, citronella, citral, 2,4-decadienal, 2-methyl-3-heptanone, 5-methyl-3-heptanone, 6-methyl-5-hepten-2-one, geranylacetone, beta-ionone, camphene, hexadecane and heptadecane. One liter water samples, salted with 100 g of sodium chloride, were extracted by microextraction using 2 x 3 mi of hexane. The extracts were analyzed by gas chromatographic-ion-trap detection-mass spectrometry (GC-ITD-MS). Mean recoveries from spiked reagent water were 99 +/- 7 and 95 +/- 8% for MIB and geosmin (spiked with 5-40 ng/l), respectively. For other compounds, recoveries ranged between 81 and 110%, with the exception of hexanal, heptanal and benzaldehyde. The method detection limits were as low as 1 ng/l for geosmin and MIB, 0.5-6 ng/l for ketones and 5-25 ng/l for other compounds. Recoveries end precision for most of the compounds investigated from spiked river water were similar to those obtained in reagent water. This method was employed for monitoring the occurrence of taste and odor compounds in the Arno River. (C) 1997 Elsevier Science Ltd.