Corona Discharge Ion Mobility Spectrometry with Orthogonal Acceleration Time of Flight Mass Spectrometry for Monitoring of Volatile Organic Compounds Martin Sabo and S ̌ tefan Matejc ̌ ík* Comenius University, Faculty of Mathematics, Physics and Informatics, Department of Experimental Physics, Mlynska dolina F2 842 48 Bratislava, Slovakia ABSTRACT: We demonstrate the application of corona discharge ion mobility spectrometry with orthogonal acceleration time of flight mass spectrometry (CD IMS-oaTOF) for volatile organic compounds (VOCs) monitoring. Two-dimensional (2D) IMS-oaTOF spectra of VOCs were recorded in nearly real time. The corona discharge atmospheric pressure chemical ionization (APCI) source was operated in positive mode in nitrogen and air. The CD ion source generates in air H 3 O + (H 2 O) n and NO + . The NO + offers additional possibility for selective ionization and for an increase of the sensitivity of monoaromatic compounds. In addition to H 3 O + (H 2 O) n and NO + , we have carried out ionization of VOCs using acetone as dopant gas ((CH 3 ) 2 COH + ). Sixteen model VOCs (tetrahydrofuran, butanol, n- propanol, iso-propano, acetone, methanol, ethanol, toluene, benzene, amomnia, dioxan, triethylamine, acetonitrile, formaldehyde, m-xylene, 2,2,2-trifluoroethylamine) were tested using these ionization techniques. T here exists increasing demand for volatile organic compounds (VOCs) monitoring and analysis in various fields of science and applications. Industrial and environmental applications require air and wastewater quality monitoring. The monitoring of pollutants is important in indoor and outdoor environments because of their impact on human health. On the other hand, the analysis of VOCs exhaled from human breath, especially those of endogenous origin, seems to be a promising method for the noninvasive diagnosis of diseases and prevention. The gas chromatography (GC) techniques like GC-flame ionization detection (GC-FI), 1 GC-infrared detection (GC-IR), 2 and GC/mass spectrometric detection (GC/MS) 3 are consid- ered as a standard for VOCs analysis due to their high sensitivity and high selectivity. However, the higher time consumption is the main drawback of the GC techniques. The supercontinuum cavity ring down spectroscopy (SCRDS) 4 is characterized by high sensitivity (sub ppb level) and relatively quick response. The requirement of tunable lasers and high reflectance mirrors, suitable for a given wavelength, complicates wider deployment of such instruments. The mass spectrometric techniques like atmospheric pressure chemical ionization mass spectrometry (APCI-MS), 5,6 proton transfer reaction mass spectrometry (PTR-MS), 7 and selected ion flow tube mass spectrometry (SIFT-MS) 8 are due to their high sensitivity and fast response preferred techniques in many applications. The fragmentation in the case of PTR-MS and APCI-MS could complicate the data analysis of more complex spectra. In order to reach high sensitivity, these devices require longer data acquisition or preconcentration techniques, which can adversely affect the time consumption. These problems could be partially solved by replacement of quadrupole MS by more expensive time-of-flight MS (TOFMS). However, even in this case, these MS techniques are not able to resolve the individual isomers. The ion mobility spectrometry (IMS), 9,10 due to its compact design, high sensitivity, and fast response, is a valuable instrument for VOCs monitoring in various applications. 11-13 However, in the case of analysis of complex mixtures, the IMS as an individual unit does not have sufficient selectivity. This problem could be partially solved by the selectivity in ionization, doping of ionization source of IMS, 14 or by interfacing IMS to other analytical instruments. The combination of IMS with other techniques is found in applications in analytical laboratories all around the world. 15-17 The successful application of GC coupled with IMS is found in air quality monitoring on the international space station, 18 while the multicolumns capillary GC (MCC- GC) IMS combination is used in medical applications for analysis of human breath. 19 The first instrument combining a drift tube and orthogonal TOF appeared in 1967 by McKnight et al. 20 and has been applied to study ion molecule reactions of nitrogen ions in N 2 . The operating conditions were different to present IMS devices; the pressure in the drift tube was only ∼133 Pa. The IMS interfaced orthogonally accelerated TOF spectrometer (IMS-oaTOF) was introduced as a high performance analytical instrument. 21 The Received: March 14, 2012 Accepted: May 17, 2012 Article pubs.acs.org/ac © XXXX American Chemical Society A dx.doi.org/10.1021/ac300722s | Anal. Chem. XXXX, XXX, XXX-XXX