Towards Real-Time Portable Gas Mass Spectroscopy Detection by Multivariate Analysis: a Case Study

Abstract

Early and significant results for a real-time, column-free miniaturized gas mass spectrometer (MS) in detecting target species with partial overlapping spectra are reported. The achievements have been possible using both nanoscale holes to be used as a nanofluidic sampling inlet system and a robust statistical technique based on multivariate analysis to build predictive models. Even if the presented physical implementation could be used with gas chromatography (GC) columns, the aim of high miniaturization requires investigating its detection performance with no GC aid. For this reason, suitable analytical models were studied to get a semi-quantitative evaluation with very low computational resources. As a study case, dichloromethane (CH2Cl2) and cyclohexane (C6H12) with concentrations in the 6-93ppm range in single and compound mixtures were used. The nano-orifice approach was able to acquire raw spectra in 60 seconds with correlation coefficients of 0.525 and 0.578 with respect to the NIST reference database, respectively. Then, we built a calibration dataset on 2277 raw spectra of 10 known different mixtures using partial least square regression (PLSR) for statistical data inference. The model showed a normalized full-scale root-mean square deviation (NRMSD) accuracy of \(10.9\text{\%}\) and \(18.4\text{\%}\) for each species, respectively, even in combined mixtures.