Measurement Device for Ambient Carbonyl Sulfide by Means of Catalytic Reduction Followed by Wet Scrubbing/Fluorescence Detection

Abstract

A portable chemical analysis system for monitoring ambient carbonyl sulfide (COS) was investigated for the first time. COS is paid attention to from the perspectives of photosynthesis tracer, breath diagnosis marker, and new process-use in the manufacture of semiconductors. Recently, the threshold level value of COS was settled at 5 ppm in volume ratio (ppmv) for workplace safety management. In this work, COS was converted to H 2 S by a small column packed with alumina catalyzer at 65 °C. Then, the H 2 S produced was collected in a small channel scrubber to react with fluorescein mercuric acetate (FMA), and the resulting fluorescence quenching was monitored using an LED/photodiode-based miniature detector. The miniature channel scrubber was re-examined to determine its robustness and easy fabrication, and conditions of the catalyzer were optimized. When the FMA concentration used was 1 μM, the limit of detection and dynamic range, which were both proportional to the FMA concentration, were 0.07 and 25 ppbv, respectively. Ambient COS in the background level and even contaminated COS in the nitrogen gas cylinder could be detected. If necessary, H 2 S was removed selectively by reproducible adsorbent columns. COS concentrations of engine exhaust were measured by the proposed method and by cryo-trap-gas chromatography-flame photometric detection, and the results obtained (0.5–5.9 ppbv) by the two methods agreed well ( R 2 = 0.945, n = 19). COS in ambient air and exhaust gases was successfully measured without any batchwise pretreatment.

Sensitive Detection of OCS Using Thermal Conversion Combined with Spectral Reconstruction Filtering Differential Optical Absorption Spectroscopy

“…Abe et al conducted a catalytic reduction of OCS to H 2 S and achieved measurement of H 2 S (OCS) using a fluorescence detector to monitor the resulting fluorescence produced by the reaction of H 2 S with other substances. 26 However, the accuracy of this method is limited by the concentration of FMA and the sensitivity of the fluorescence detection. Due to its advantages of noninvasive measurement, high sensitivity, and fast response, spectral analysis is widely applied in trace gas measurements.…”

“…Unfortunately, this approach does not allow for individual monitoring of OCS. Abe et al conducted a catalytic reduction of OCS to H 2 S and achieved measurement of H 2 S (OCS) using a fluorescence detector to monitor the resulting fluorescence produced by the reaction of H 2 S with other substances . However, the accuracy of this method is limited by the concentration of FMA and the sensitivity of the fluorescence detection.…”

Photoacoustic trace gas detection of OCS using a 2.45 mL Helmholtz resonator and a 4823.3 nm ICL light source

“…Common OCS detection methods can be divided into two main categories: non-optical and optical method. Non-optical method include gas chromatography [10] , [11] , fluorescence detection [12] , [13] , etc. For example, Joaquin et al built an OCS detection system based on flame ionization and chromatography for the detection of OCS gas [11] ; Kodai et al proposed a method based on fluorescence detection and construct a miniature gas analysis system, which has good sensing performance for OCS in ambient air and industrial exhaust gas.…”

“…For example, Joaquin et al built an OCS detection system based on flame ionization and chromatography for the detection of OCS gas [11] ; Kodai et al proposed a method based on fluorescence detection and construct a miniature gas analysis system, which has good sensing performance for OCS in ambient air and industrial exhaust gas. [12] . These researches show that the non-optical methods can achieve high-sensitive detection.…”