Application of Ion-Mobility Spectrometry to Chemical Analysis at High Concentrations

Abstract

Ion-mobility spectrometry (IMS) can perform qualitative and quantitative analysis of multicomponent chemical mixtures in real time, which is difficult for commonly used instruments such as gas chromatography–mass spectrometry and photo-ionization detectors. IMS is commonly applied in microanalytical (ppb) sensing of toxic gases. Thus, its application to quantitative analyses of chemical substances with a high proton affinity is generally not possible at high concentrations (~1000 ppm) because multimeric complexes are generated. In a previous study, we found that calibration curves derived from shifts in nominal arrival-time spectra of chemical substances overlapping with water clusters enable quantitative analysis at high concentrations. This study investigated the applicability of high-concentration quantitative analysis using IMS, including the lower and upper limits of quantification and their chemical dependence on methyl ethyl ketone and ethanol. We found that the magnitude of the shift in the nominal arrival-time spectrum at low concentrations is different from that at high concentrations, and that the concentration of a chemical substance can be determined with high precision from the shift in the arrival-time spectrum, even at low concentrations. Proton affinity has a significant effect on spectral shift and quantification limits. Our results indicate that shifts in nominal arrival-time spectra allow accurate quantitative analysis at both low and high concentrations. Our calibration technique is derived from the shift in nominal peaks including multimeric complexes at high concentrations, which resultantly recognized the highest dynamic range ever. We could measure the dynamic range of chemical substances over three orders using this method.