Mold Odor in Tap Water

Japanese tap water is well regarded in terms of drinking water quality, but in recent years mold odor has become an issue. This mold odor is known to be caused by 2–methylisoborneol and diosmin.
The odor threshold of these compounds is about 10 ppt and they cannot be directly detected by measurements in a gas chromatograph-mass spectrometer (GC/MS). As indicated in the Drinking Water Test Method, they must be concentrated using the purge & trap method before measurement by GC/MS.

Reference

(1) Drinking Water Test Method & Explanation; edited by Japan Water Works Association
(2) Environmental Water Quality Analysis Manual; edited by Japan Society for Environmental Chemistry

Gas Chromatograph Mass Spectrometer

This instrument is widely used for the qualitative and quantitative analysis of chemical substances. The column and ionization method are selected to suit the analysis target components. The purge & trap method concentrates a sample by 100x to 1000x. Unknown components are easily identified using mass spectra of the peaks in the total ion chromatogram (TIC).