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.

1-Bromo-2,3,6-trichloro-4,5-dimethoxybenzene

“…For similar structures of halogenated methoxy benzenes, see: Iimura et al (1984); Rissanen et al (1987Rissanen et al ( , 1988a; Song et al ( , 2010; Telu et al (2008); Weller & Gerstner (1995); Wieczorek (1980). For background to halogenated methoxy benzenes, see: Brownlee et al (1993); Curtis et al (1972); Pereira et al (2000); Vlachos et al (2007); Zhang et al (2006). Cu K radiation = 11.94 mm À1 T = 90 K 0.20 Â 0.15 Â 0.07 mm…”

“…Chlorinated methoxy benzenes are a group of persistent organic pollutants that are associated with off-flavors in water, fish, chicken and wine (Brownlee et al,1993;Curtis et al, 1972;Pereira et al, 2000;Vlachos et al, 2007;Zhang et al, 2006). Their biological properties depend, at least in part, on the conformation of the methoxy group relative to the aromatic ring system.…”

1,3,5-Trichloro-2-methoxybenzene

“…For similar structures of anisoles with two ortho-chloro substituents, see: Rissanen et al (1987); Weller & Gerstner (1995); Wieczorek (1980). For other related literature, see: Brownlee et al (1993); Curtis et al (1972); Iimura et al (1984); Kolehmainen & Knuutinen (1983); Oswald et al (2005); Pereira et al (2000); Rissanen et al (1988); Vlachos et al (2007); Zhang et al (2006).…”

“…Chlorinated anisoles are persistent environmental pollutants known for their toxicity and tendency to bioaccumulate (Brownlee et al, 1993). Especially anisoles with chlorine substitution in the 2-and 6-position are a well known cause for off-flavors in water, fish and chicken eggs (Brownlee et al, 1993;Curtis et al, 1972;Zhang et al, 2006). The title compound is a major contributor to "cork taint", a well known off-flavor in the wine industry (Pereira et al, 2000;Vlachos et al, 2007).…”

Application of SPE followed by large-volume injection GC/MS for the analysis of geosmin and 2-methylisoborneol in water

“…29 An easy way to overcome the above-mentioned limitation is injecting a sample of larger volume than typical injection, e.g., 1 mL. Recently, a programmable temperature vaporizing (PTV) technique was developed to facilitate large-volume injection (LVI), [30][31][32] resulting in signicantly improved sensitivity of GC analysis. For example, sub-ppt levels of 2-MIB and geosmin in water could be determined using CLLE coupled with GC/MS equipped with a PTV device.…”