The Determination of Geosmin and 2-Methylisoborneol Using Stable Isotope Dilution Purge-and-Trap Gas Chromatography Mass Spectrometry

An isotope dilution technique based on purge-and-trap coupled to gas chromatography with mass spectrometric detection were developed and optimized for the trace determination of the typical odorous compounds; Geosmin (GSM) and 2-methylisoborneol (Mm). The selection of quantitative ion and the factors of programmed temperature, the sample purge temperature, salinity on the extraction of odor compounds were discussed. D-5-Geosmin and d(3)-MIB as the isotopes internal standards are added to the 25ml of water sample containing sodium chloride (20%(m/v)), and the analytes were purged at 60 degrees C by a flow of N-2 in 13min and trapped on a Tenax-Silica Gel-Charcoal sorbent, then separated and determined by gas chromatograph coupled to a mass spectrometer. Under the optimal conditons, the calibration curves of MIB and GSM were linear in the range of 5-500ng/L, with a correlation coefficient above 0.9998. The limits of detection (LOD) were 4.12ng/L for MIB and 3.60ng/L for GSM. Recovery were 82%similar to 95% for GSM and 99%similar to 101% for MIB, and precision were 5.20% for GSM and 0.78% for MIB at 100ng/L from a reservior source water sample in Fuzhou, China. This method was applied to the analysis of environmental water samples successfully.