Picogram determination of "earthly-musty" odorous compounds in water using modified closed loop stripping analysis and large volume injection GC/MS.

"Earthy-musty" off-flavor problems in water samples are due to organic compounds present at the sub-part-per-trillion level. Numerous analytical methods such as purge and trap, liquid/liquid extraction, and closed-loop stripping analysis (CLSA) followed by GC/MS analysis have been used to determine these compounds. However, these methods offer poor sensitivity (detection limits of approximately 1 to 10 ng/L) when compared to the 20-30 pg/L of sensorial sensitivity. The purpose of this study was to develop a new method involving a modified CLSA preconcentration technique together with large volume injection GC/MS in order to attain analytical sensitivity equal to or better than olfactory sensitivity. For eight target compounds that cause taste and odor problems in water at trace levels, the method developed was linear in the 0.05-10 ng/L range and provided recoveries greater than 70% together with satisfactory repeatability. Detection limits as low as 15-30 pg/L were achieved, representing a 50-fold improvement in sensitivity as compared to current methods. The accuracy and sensitivity of the method were demonstrated in different aqueous matrixes, including raw surface water. The method was successfully applied to earthy-musty water samples that had remained unsolved by conventional techniques, thus proving its effectiveness.