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The highly odorous compound methanethiol, CH 3 SH, is commonly produced in biodegradation of biomass and industrial processes, and is classed as 2000 times more odorous than NH 3 . However, there is no simple analytical method for detecting low parts-per-billion in volume ratio (ppbv) levels of CH 3 SH. In this study, a micro gas analysis system (μGAS) was developed for continuous or near real time measurement of CH 3 SH at ppbv levels. In addition to a commercial fluorescence detector, a miniature high sensitivity fluorescence detector was developed using a novel micro-photomultiplier tube device. CH 3 SH was collected by absorption into an alkaline solution in a honeycomb-patterned microchannel scrubber and then mixed with the fluorescent reagent, 4-( N , N -dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F). Gaseous CH 3 SH was measured without serious interference from other sulfur compounds or amines. The limits of detection were 0.2 ppbv with the commercial detector and 0.3 ppbv with the miniature detector. CH 3 SH produced from a pulping process was monitored with the μGAS system and the data agreed well with those obtained by collection with a silica gel tube followed by thermal desorption–gas chromatography–mass spectrometry. The portable system with the miniature fluorescence detector was used to monitor CH 3 SH levels in near-real time in a stockyard and it was shown that the major odor component, CH 3 SH, presented and its concentration varied dynamically with time. |
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