Analysis of off-flavor compounds in water at sub part per trillion level by GC/MS with programmable temperature vaporizer inlet

Abstract

"Earthy-musty" off-flavor problems in water samples are due to organic compounds present at the sub part per trillion level. Most of the studies in the analysis of tastes and odorous compounds focus on the extraction pre concentration technique, with detection at picogram per liter level of the earthy-musty off-flavor compounds, which are difficult to achieve. The objective of this study is to develop a new method involving the GC/MS with programmable temperature vaporizer (PTV) inlet via large volume injection (LVI) or solid phase micro-extraction (SPME), to attain analytical sensitivity equal to or better than olfactory sensitivity. Six "earthy-musty" organic compounds; 2-methylisoborneol (MIB); geosmin; 2, 4, 6-trichloroanisole (2,4,6-TCA); 2, 3, 6-trichloroanisole (2,3,6-TCA); 2, 3, 4-trichloroanisole (2,3,4-TCA); and 2, 4, 6-tribromoanisole (2,4,6-TBA), were used as probes for this study. It was found that LVI via PTV could greatly improve system sensitivity towards the detection of off-flavor compounds with low volatility such as haloanisoles. For those off-flavor compounds with high volatility, eg MIB, SPME coupled with PTV-GC-MS with cool initial temperature has always demonstrated the best sensitivity.