A LIQUID/LIQUID EXTRACTION PROCEDURE FOR TASTE AND ODOUR COMPOUND ANALYSIS

摘要

The Metropolitan Toronto Water Supply has experienced sporadic episodes of taste andrnodour (T&O) during the past several years. This led to the requirement for a simple analyticalrnprocedure to assess the presence of possible source compounds.rnA simple procedure utilizing available equipment for the analysis of Geosmin and 2-rnMethylisoborneol (MIB) was targeted. A quick turnaround time was also required. ArnDichloromethane Liquid/Liquid Extraction (LLE) procedure followed with detection by GasrnChromatography-Mass Spectrometer-Selected Ion Monitoring (GC-MS-SIM) was proposed.rnAn analytical procedure for the determination of Geosmin and MIB with a MethodrnDetection Limit (MDL) = 10 ng/L was established in 1994. The results were similar to thosernobtained by a more costly procedure involving an Ambersorb extraction and High-ResolutionrnMass Spectrometer detection. Turnaround time for up to 11 samples was 1-2 days. This wasrnmore effective than the use of Closed-Loop Stripping Analysis (CLSA) which would only havernprocessed 1-2 samples per day. During the three T&O episodes in 1994, Geosmin was detectedrnat concentrations of up to 60-70 ng/L.rnExtensive (almost daily) analyses for Geosmin and MIB were carried out in the summerrnand fall of 1995. However, no T&O episodes occurred during that period. Geosmin wasrndetected at levels below u001020 ng/L, and was mostly present at trace levels only. MIB levels forrnboth years were not significant.rnFour serious T&O episodes occurred in 1996. Only trace levels of Geosmin and no MIBrnwere detected. The analyses of other possible T&O compounds were hence established.rnAnisole, 2-Isopropyl-3-methoxypyrazine, 2,4-Dichloroanisole, 2,4,6-Trichloroanisole and 2,3,6-rnTrichloroanisole were analysed using a similar procedure. MDL’s of 10 ng/L and recoveries ofrn80% were typical. Significant levels of 2,4,6-Trichloroanisole (up to 20 ng/L) were observed inrnconjunction with reports of T&O.rnThe simple LLE-GC-MS-SIM procedure is resource effective and can be applied to therndetermination of several T&O compounds. Standard preparatory techniques and equipment canrnbe effectively applied to this often specialized analysis.