Effect of Carrier Gas on Sensitivity of Surface Acoustic Wave Detector

Enhancement of sensitivity is a hot pursuit for every kind of sensor/detector. While many methods are exploited for various sensors/detectors for this, the methods are specific in nature for the technology involved. This article discusses a novel study where enhancement of sensitivity, specific to a Surface Acoustic Wave (SAW) device used as a Gas Chromatographic (GC) detector is achieved by using a proper carrier gas. With an ultimate aim of implementing the outcome on SAW-GC based, handheld, Chemical Warfare Agent (CWA) Electronic-Nose vapour detector being developed at our laboratory, four different carrier gases i.e. Hydrogen, Helium, Nitrogen and Zero air were subjected to the scrutiny for its impact on sensitivity. Detection of a CWA simulant, 2-Chloro-Ethyl-Ethyl-Sulfide (CEES), 1,5-Dichloropentane (DCP) simulating Sulphur Mustard (H Agent), Di-methylmethyl phosphonate (DMMP), Diethyl cyanophosphonate (DECP), Triethyl pohosphate (TEP) simulating G-Agents along with three Volatile Organic Compounds (VOCs) i.e. Methanol, Toluene and Xylene were carried out in the study. A fast-GC with 70 seconds chromatogram, with appropriate GC parameters is used for the study in order to cater for the handheld battery operated rapid detector. A spread of more than two times in sensitivity could be seen while using common GC carrier gases in the range of concentration (200-2000ppm) studied. By virtue of GC with SAW detector, excellent selectivity, repeatability, and long term stability is achieved. A detailed discussion on the reasons for the same is presented.