We propose a portable chemical analysis system capable of identifying chemical substances at trace concentrations (sub-ppm), even in case of a complex matrix of interfering species. This is achieved by means of the bi-dimensional selectivity obtained through the combination of gas-chromatographic (GC) separation and photoacoustic (PA) infrared analysis, in particular quartz-enhanced PA spectroscopy (QEPAS). The GC module is preferentially a MEMS-based FAST-GC device, capable of separating complex and low volatility samples within a short time (few minutes) and on a reduced thermal budget. The QEPAS module is preferentially built around an analysis cell with a microscopic internal volume, capable of processing, with high sensitivity and excellent selectivity very small vapor flows, as typically eluting from a FAST-GC column.
The GC/QEPAS system is a high-end vapor analysis system, relying on the bi-dimensional selectivity of gas-chromatographic separation coupled to a spectroscopic detector. While such combination is already frequently used in laboratory equipment, most notably as GC/MS (gas-chromatography and mass spectroscopy), those systems are complex, expensive and not suitable for portable implementations or in-field analyses, mainly due to the fragility of the ultra-high vacuum pumps necessary for the MS system. The combination of a MEMS-based FAST-GC system with a specifically designed infrared absorption spectroscopy system enables sensing performances similar to GC/MS systems, but in a miniaturized, portable and robust systems. This technology is suitable to rapidly detect in-field specific substances at trace concentrations, even inside a complex interfering sample matrix.
Italy, PCT