Detection of Atmospheric Methyl Mercaptan Using Wavelength Modulation Spectroscopy with Multicomponent Spectral Fitting.

Jinyi Li,Gang Luo,Yiwen Ma,Hong Gao,Jiaxin Wan,Zhenhui Du

doi:10.3390/s17020379

Abstract

Detection of methyl mercaptan (CH3SH) is essential for environmental atmosphere assessment and exhaled-breath analysis. This paper presents a sensitive CH3SH sensor based on wavelength modulation spectroscopy (WMS) with a mid-infrared distributed feedback interband cascade laser (DFB-ICL). Multicomponent spectral fitting was used not only to enhance the sensitivity of the sensor but also to determine the concentration of interferents (atmospheric water and methane). The results showed that the uncertainties in the measurement of CH3SH, H2O, and CH4 were less than 1.2%, 1.7% and 2.0%, respectively, with an integration time of 10 s. The CH3SH detection limit was as low as 7.1 ppb with an integration time of 295 s. Overall, the reported sensor, boasting the merits of high sensitivity, can be used for atmospheric methyl mercaptan detection, as well as multiple components detection of methyl mercaptan, water, and methane, simultaneously.

Highlights

Methyl mercaptan, a colorless gas with a foul odor, is produced by both natural [1] and industrial sources [2]
A high-sensitivity sensor based on wavelength modulation spectroscopy (WMS) with a distributed feedback interband cascade laser (DFB-interband cascade laser (ICL)) as the optical source and an HWG as the gas cell was presented for atmospheric CH3SH measurement
The multicomponent spectral fitting was used to eliminate the influence of the atmospheric interferents, H2O and CH4, in CH3SH

Summary

Introduction

Methyl mercaptan (methanethiol, CH3 SH, MM), a colorless gas with a foul odor, is produced by both natural [1] and industrial sources [2]. The olfactory threshold of MM is very low (~2 ppb). It is significantly toxic at high concentrations and can destroy the central nervous system of living beings. The recommended threshold concentration limit of MM, as defined by the American. Conference of Governmental Industrial Hygienists (ACGIH), is 0.5 ppm (threshold limit value: 8 h time weighted average; TLV-TWA) [3]. CH3 SH is a predominant marker in exhaled breath (ppm levels) for the diagnosis of periodontal and stomach diseases [4,5]. It is necessary to monitor CH3 SH continuously from ppb to ppm levels for purposes of environmental monitoring and biomedical diagnosis

Methods

Results

Conclusion