Use of solid phase microextraction (SPME) in the analysis of the reduced sulfur compounds (RSC) and its experimental limitations

Abstract

In this study, techniques based on solid-phase microextraction (SPME) with gas chromatography (GC)–pulsed flame photometric detection (PFPD) were evaluated for its application toward a list of reduced sulfur compounds (RSCs) such as hydrogen sulfide (H2S), methanethiol (CH3SH), dimethyl sulfide (DMS), carbon disulfide (CS2), and dimethyl disulfide (DMDS). Its performance was tested against direct injection (DI) and thermal desorber (TD) approaches. Although the SPME-based calibration of RSCs showed good linearity (r2 > 0.9) like other methods, it was more prone to analytical bias for the lighter molecular weight (MW) RSCs (especially H2S) due to distinctively reduced sensitivity relative to the heavier MW compounds. As such, the detections limits (DL) of SPME vary by more than an order of magnitude for the lighter and heavier MW RSCs (DL = 16.9 ng for H2S and 1.46 ng for DMS). Evidence collected from an extended reproducibility test further supports that the experimental reliability of SPME approach is fairly low, especially with respect to H2S. The quality of SPME-based analysis thus needs more cautious validation in the study of odor and air pollution, as the lighter RSCs like H2S (or CH3SH) are often identified as the key components under various settings.