Rapid detection of taste and odor compounds in water using the newly invented chemi-ionization technique coupled with time-of-flight mass spectrometry.

Taste and odor (T&O) compounds are widespread in water environments and have attracted considerable public attention. Nowadays, the standard detections of these chemicals rely mainly on off-line methods such as GC-MS or evaluation by trained analysts' senses. In this study, we report a method for the rapid detection of T&O compounds in water by exploiting a newly invented chemi-ionization source, in combination with headspace vapor measurement at room temperature. The calibrated limits of detection (LODs) of 2-methylbutyraldehyde, methyl tert-butyl ether (MTBE), methyl methacrylate (MMA), 2-isobutyl-3-methyoxypyrazine (IBMP), and 2-isopropyl-3-methoxypyrazine (IPMP) are in the range of 3.5-50.2 ng L-1 , and the estimated LODs of 2-methylisoborneol (2-MIB) and geosmin (GSM) are 0.25 and 0.77 ng L-1 , respectively. The calibration results reveal that the instrumental LODs for 2-methylbutyraldehyde, MTBE, MMA, β-cyclocitral, 2-MIB, and GSM are 1-2 orders of magnitude better than the odor thresholds of humans. The accuracy, precision, recovery, and linearity (R2 ) of the method are tested. Water samples from city tap water and three rivers in Beijing are assessed using this technique, and the typical T&O compositions are observed with concentrations ranging from 0.2 to 297 ng L-1 . The new ultra-sensitive rapid detection method shows comparable sensitivities to the existing off-line technique and displays great potential for real-time detection of T&O pollution in water environments.