Determination of C1-C4 alkanes by ion mobility spectrometry

Strategy for the identification of flavor compounds in e-liquids by correlating the analysis of GCxIMS and GC-MS

This work presents a strategy to correlate the results from gas chromatography coupled ion mobility spectrometry (GCxIMS) and mass spectrometry (GC-MS) to enable a simpler and cheaper analysis of flavor compounds in e-liquids. The use of the retention index for GCxIMS measurements was validated for its application to correlate results with GC-MS data. The easy detection of the GCxIMS for substances at concentrations as low as 1 μg/L can therefore be combined with the identification power of the MS. The use of the MS' mass signals and wide-spread availability of mass spectra libraries reduces the effort necessary to choose the correct reference standards for the identification of unknown substances. Between both detectors, correlating of the retention time indices was achieved for ± 1%. 2-Alkanones were used as an alternative reference point for the IMS and the well-established alkanes for the MS. The application on flavor compounds in e-liquids shows equal or better results than those presented for more complex, hardware-based correlations like line splitting. Additionally, the inverted reduced mobility combined with the retention index of a non-polar column enables simple extrapolation for the confirmation of expected substances as well as the use in a transferable database. For the first time, this comprehensive application allows an extensive, simplified, and cheap identification of flavor compounds in e-liquids by GCxIMS and GC-MS.

Mercury-induced fragmentation of n-decane and n-undecane in positive mode ion mobility spectrometry

Ion mobility spectrometry is a well-known technique for trace gas analysis. Using soft ionization techniques, fragmentation of analytes is normally not observed, with the consequence that analyte spectra of single substances are quite simple, i.e. showing in general only one peak. If the concentration is high enough, an extra cluster peak involving two analyte molecules can often be observed. When investigating n-alkanes, different results regarding the number of peaks in the spectra have been obtained in the past using this spectrometric technique. Here we present results obtained when analyzing n-alkanes (n-hexane to n-undecane) with a pulsed electron source, which show no fragmentation or clustering at all. However, when investigating a mixture of mercury and an n-alkane, a situation quite typical in the oil and gas industry, a strong fragmentation and cluster formation involving these fragments has been observed exclusively for n-decane and n-undecane.

Penning ionization electron spectroscopy in glow discharge: another dimension for gas chromatography detectors

Admixtures to helium of 100 and 5 ppm of nitrogen, and 100 and 10 ppm of carbon monoxide were identified and measured in the helium discharge afterglow using an electrical probe placed into the plasma. For nitrogen and carbon monoxide gases, the measured electron energy spectra display distinct characteristic peaks (fingerprints). Location of the peaks on the energy scale is determined by the ionization energies of the analyte molecules. Nitrogen and carbon monoxide fingerprints were also observed in a binary mixture of these gases in helium, and the relative concentration of analytes has been predicted. The technically simple and durable method is considered a good candidate for a number of analytical applications, and in particular, in GC and for analytical flight instrumentation.

Gas chromatography in space

Gas chromatography has proven to be a very useful analytical technique for in situ analysis of extraterrestrial environments as demonstrated by its successful operation on spacecraft missions to Mars and Venus. The technique is also one of the six scientific instruments aboard the Huygens probe to explore Titan's atmosphere and surface. A review of gas chromatography in previous space missions and some recent developments in the current environment of fiscal constraints and payload size limitations are presented.

Atmospheric pressure chemical ionization of alkanes, alkenes, and cycloalkanes

Normal and cyclic alkanes and alkenes form stable gas-phase ions in air at atmospheric pressure from 40 to 200°C when moisture is below 1 ppm. Ionization of alkanes in a (63)Ni source favored charge transfer over proton transfer through pathways involving [M-1](+) and [M-3](+) ions. Ion mobility spectra for alkanes showed sharp and symmetrical profiles while spectra for alkenes suggested fragmentation. Ion identifications were made by using mass spectrometry, and ionization pathways were supported by using deuterated analogs of alkanes and alkenes. Alkanes were ionized seemingly through a hydrogen abstraction pathway and did not proceed through an alkene intermediate. New methods for interpretation of mobility spectra utilizing ion mobility spectrometry, atmospheric pressure chemical ionization mass spectrometry, chemical ionization mass spectrometry, and ion mobility spectrometry-mass spectrometry data were demonstrated.