Evaluation of coating materials used on piezoelectric crystals for the detection of dimethyl sulfide in liquefied petroleum gas

Abstract

Coated piezoelectric crystals (PZX) were applied to the detection of the stenching agent dimethyl sulfide (DMS) and its oxidation products, dimethyl sulfoxide (DMSO) and dimethyl sulfone (DMSO₂) in a butane carrier gas stream. Over 39 stationary phase, metal and lipid multibilayer coating materials have been evaluated for potential gas detection of the target analytes. Good reversibility and fast response times (2 s–2 min) were exhibited by all coating materials evaluated but sensitivity towards DMS was poor (10000 ppm). There is, however, some evidence for the sorption of butane as the coated PZX is introduced into the gas stream. Both the oxidation products, DMSO and DMSO₂, provide positive changes in resonant frequency for every coating material evaluated, instead of the expected negative frequency response produced by DMS. This indicates the removal of previously sorbed species, possibly a butane adlayer. Reversibility and fast response times (2 s–1 min) were observed. The DMSO could be determined down to 10 ppm in butane with squalane as the coating.