15 - Gas detection by quartz enhanced photoacoustic spectroscopy

Abstract

Photoacoustic spectroscopy is a detection method in which the light source energy is converted to sound [1], subsequently the sound captured by microphone. This method can be used for quantitative chemical analysis at ultra-low concentrations of gaseous species or samples with low absorption coefficient. Quartz enhanced photoacoustic spectroscopy replaces the classical conventional microphone and enables rapid and highly sensitive detection of trace gas concentrations, when using quartz tuning fork with a high quality factor [2]. Tunable quantum cascade laser partly covering acetonitrile infrared spectra [3] was employed in this study as an excitation source for quartz enhanced photoacoustic spectroscopy. Vapor of acetonitrile was used as measuring gas. From the practical point of view this gas is of importance as a marker of explosive compounds such as trinitrotoluene and hexogen [4], or it can be released into the atmosphere during combustion of biomass [5]. Case specific design of the photoacoustic cell and experimental setup for the purposes of quantum cascade laser -quartz enhanced photoacoustic spectroscopy detection is finally reported within this work.