Detection of gaseous compounds by needle trap sampling and direct thermal-desorption photoionization mass spectrometry: Concept and demonstrative application to breath gas analysis.

A fast detection method to analyze gaseous organic compounds in complex gas mixtures was developed, using a needle trap device (NTD) in conjunction with thermal-desorption photoionization time-of-flight mass spectrometry (TD-PI-TOFMS). The mass spectrometer was coupled via a deactivated fused silica capillary to an injector of a gas chromatograph. In the hot injector the analytes collected on the NTD were thermally desorbed and directly transferred to the PI-TOFMS ion source. The molecules are softly ionized either by single photon ionization (SPI, 118 nm) or by resonance enhanced multiphoton ionization (REMPI, 266 nm) and the molecular ion signals are detected in the TOF mass analyzer. Analyte desorption and subsequent PI-TOFMS detection step only lasts ten seconds. The specific selectivity of REMPI (i.e. aromatic compounds) and universal ionization characteristics render PI-MS as a promising detection system. As a first, demonstrative application alveolar-phase breath gas of healthy, non-smoking subjects was sampled on NTDs. While smaller organic compounds as acetone, acetaldehyde, isoprene or cysteamine can be detected in the breath gas with SPI, REMPI depicts the aromatic substances phenol and indole at 266 nm. In breath gas of a healthy, smoking male subject, several xenobiotic substances such as benzene, toluene, styrene and ethylbenzene can be found as well. Furthermore, the NTD-REMPI-TOFMS setup was tested for breath gas taken from a mechanically ventilated pig under continuous intravenous propofol (2,6-diisopropylphenol, narcotic drug) infusion

Investigation of the Photoionization Properties of Pharmaceutically Relevant Substances by Resonance Enhanced Multiphoton Ionization Spectroscopy and Single Photon Ionization Spectroscopy Using Synchrotron Radiation

The photoionization properties of the pharmaceutically relevant substances amantadine, diazepam, dimethyltryptamine, etomidate, ketamine, mescaline, methadone, and propofol were determined. At beamline U125/2-10m-NIM of the BESSY II synchrotron facility (Berlin, Germany) vacuum ultraviolet (VUV) photoionization spectra were recorded in the energy range 7.1 to 11.9 eV (174.6 to 104.2 nm), showing the hitherto unknown ionization energies and fragmentation appearance energies of the compounds under investigation. Furthermore, (1+1)-resonance-enhanced multiphoton ionization (REMPI) spectra of selected compounds (amantadine, diazepam, etomidate, ketamine, and propofol) were recorded by a continuous scan in the energy range between 3.6 and 5.7 eV (345 to 218 mu) using a tunable optical parametric oscillator (spectral resolution: 0.1 mu) laser system. The resulting REMPI wavelength spectra of these compounds are discussed and put into context with already known UV absorption data. Time-of-flight mass spectrometry was used for ion detection in both experiments. Finally, the implications of the obtained physical-chemical results for potential analytical applications are discussed. In this context, fast detection approaches for the considered compounds from breath gas using photoionization mass spectrometry and a rapid pre-concentration step (e.g., needle trap device) are of interest

Needle trap sampling thermal-desorption resonance enhanced multiphoton ionization time-of-flight mass spectrometry for analysis of marine diesel engine exhaust.

The aim of this publication is to present the results of the ship diesel engine measurement campaign in Rostock. A single-cylinder diesel research engine was operated on different engine loads and two different fuel types-diesel fuel (DF, diesel DIN-EN 590) and heavy fuel oil (HFO 180). The gaseous phase was directly trapped on needle trap devices (NTDs), thermal desorbed in a GC inlet and analyzed by resonance enhanced multiphoton ionization time-of-flight mass spectrometry (REMPI-TOFMS). The photoionization was realized using two different wavelengths-266 nm and 248 nm. With REMPI mainly aromatic substances are softly ionized, thus, especially aromatics and polycyclic aromatic hydrocarbons (PAH) were found in gaseous samples of exhaust. Differences between the two fuel qualities are obviously visible. While DF exhaust contains smaller molecules (mass-to-charge ratio between 75 and 220) higher molecular substances (up to m/z 280) were found in exhaust of HFO. For example, benzene and its methylated derivatives were detected only in the diesel exhaust. Phenanthrene and alkylphenanthrenes are the major compounds resulting from combustion of heavy fuel oil. For confirmation of measured substances in exhaust the modified gas chromatographic device was complemented by a GC column. This journal i