Automated trace determination of earthy-musty odorous compounds in water samples by on-line purge-and-trap–gas chromatography–mass spectrometry

An automated technique based on purge-and-trap coupled to gas chromatography with mass spectrometric detection has been developed and optimized for the trace determination of five of the most important water odorants; 2-isopropyl-3-methoxypyrazine, 2-isobutyl-3-methoxypyrazine, 2-methylisoborneol, 2,4,6-trichloroanisole and geosmin. The extraction method was absolutely solvent-free. Analytes were purged from 20 ml of water sample containing sodium chloride at room temperature by a flow of He and trapped on a Tenax sorbent. The desorption step was performed with helium and temperature programming and desorbed analytes were directly transferred to a gas chromatograph coupled to a mass spectrometer for separation and determination. The method was reproducible (RSD < 8%) and linear over the calibration range (10–200 ng l−1). The relative recoveries of the analytes from ground water sample were calculated and were between 80 and 103% and limits of detection (LOD) below odor thresholds were achieved for most of the compounds.