Automated ultratrace determination of musty odiferous compounds from environmental waters by online purge and trap (P&T) gas chromatography–mass spectrometry (GC–MS)

Abstract

Odoriferous compounds are troublesome in natural waters in many parts of the world. The simultaneous determination of these complex compounds due to their low sample concentration and odor thresholds has been difficult. A simple, sensitive and automated technique for the determination of eight odoriferous compounds from aqueous samples was developed using online purge and trap (P&T) coupled to gas chromatography with mass spectrometry. P&T was selected to extract and purify the water samples. Several parameters that affect the extraction and concentration performance were investigated, including the trap sorbent, ionic strength, purge time, sample temperature and desorption time. Under the optimal conditions, the adsorption capacity for the Tenax TA sorbent to 2-isopropyl-3-methoxypyrazine, 4-chloroanisole, 2-isobutyl-3-methoxypyrazine, 2-methylisoborneol, 2-tert-butylphenol, 2,4-dichloroanisole, 2,4,6-trichloroanisole and geosmin reached an equilibration when sample volume was 25 ml at a concentration of 150.0 μg/l. The method provided good linearity in the range from 1.0 to1000 ng/l and the limits of detection were from 0.1 to 0.3 ng/l, which are below the odor thresholds for most of these compounds. The proposed method was applied to the determination of eight odoriferous compounds in surface and tap waters with recoveries from 74.7% to 112.8% and relative standard deviations from 2.6% to 10.8%. This method may be widely employed for monitoring odoriferous compounds in water samples.