Fabry-Pérot cavity sensor-based optofluidic gas chromatography using a microfabricated passive preconcentrator/injector

Abstract

This study reports on dual on-column Fabry-Pérot (FP) cavity sensor-based gas chromatography (GC) of mixtures of volatile organic compounds (VOCs) utilizing an on-chip device, the so called “microfabricated passive preconcentrator/injector (μPPI)”. Comprehensive analysis of the sampling, desorption/injection, and compound separation performance of the μPPI-based optofluidic GC system is described. Here, the combined use of the μPPI and on-column FP cavity sensors in a common GC platform enabled diffusion-based passive sampling, rapid (<7 min) chromatographic separation, and optical detection for the quaternary VOC mixtures of benzene, TCE, toluene, and m-xylene at sub-ppm concentrations with a simpler fluidic setup than conventional GC systems. The FP cavity sensor arrangement provided the means to study the dynamics of the thermal desorption/injection of VOCs by the μPPI and its effect on the GC separation resolution. Our analysis of obtained chromatograms revealed a presence of the competitive adsorptions of VOC mixtures onto the adsorption sites of trapping materials in the μPPI, which decreased the effective sampling rate by ∼50% for compounds with high volatility. The validated performance of the optofluidic GC system promises future development of a field deployable GC microsystem incorporating the μPPI and the FP cavity sensors.