- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Modification of an atmospheric pressure photoionization source for online analysis of exhaled breath coupled with quadrupole time-of-flight mass spectrometry
摘要： Breath analysis is a promising method for metabolomics studies and clinical diagnosis, as it enables the observation of metabolites in a convenient and noninvasive way. In this work, an atmospheric pressure photoionization (APPI) source was modified for online analysis of exhaled breath by coupling with quadrupole time-of-flight mass spectrometry (QTOFMS). Three parameters, namely, the capillary voltage, the sampling flow and the curtain gas flow of the APPI source, were optimized. Five healthy volunteers, three males and two females, were enrolled to test the performance of modified APPI-QTOFMS by analyzing their exhaled breath. A total of 21 compounds were tentatively identified, and four metabolites, namely, dimethyl selenoxide, δ-valerolactam, hydroxymandelic acid and palmitic amide were detected in the exhaled breath for the first time. The result shows that modified APPI-QTOFMS can be used for the online study of exhaled breath.
关键词： QTOFMS,Breath analysis,Modified APPI
更新于2025-09-23 15:19:57
-
Direct inlet probe atmospheric pressure photo and chemical ionization coupled to ultra-high resolution mass spectrometry for the description of lignocellulosic biomass
摘要： Lignocellulosic biomass, in particular wood, is a complex mixture containing cellulose, hemicellulose, lignin, and other trace compounds. Chemical analysis of these biomasses, especially lignin components, is a challenge. Lignin is a highly reticulated polymer that is poorly soluble and usually requires chemical, enzymatic, or thermal degradation for its analysis. Here, we studied the thermal degradation of lignocellulosic biomass using a direct insertion probe (DIP). DIP was used with two ionization sources: atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) coupled to ultra-high-resolution mass spectrometry. Beech lignocellulosic biomass sample were used to develop the DIP-APCI/APPI methodology. Two other wood species (maple and oak) were analyzed after optimization of DIP parameters. The two ionization sources were compared at first and showed different response towards beech sample, according to the source specificity. APPI was more specific to lignin degradation compounds, whereas APCI covered a larger variety of oxygenated compounds, e.g., fatty acids, polyphenolics compounds, in addition to lignin degradation products. The study of the thermo-desorption profile gave information on the different steps of lignocellulosic biomass pyrolysis. The comparison of the three feed sample types (oak, maple, and beech), using principal component analysis (PCA) with DIP-APCI experiments, showed molecular level differences between beech wood pellets and the two others wood species (maple and oak).
关键词： high-resolution mass spectrometry,APPI,APCI,direct inlet probe,biomass
更新于2025-09-19 17:13:59
-
Reference Module in Chemistry, Molecular Sciences and Chemical Engineering || Photoionization
摘要： The ionization of analyte molecules is of vital importance to mass spectrometric analysis because mass spectrometry takes only ions as the object for analysis. The most commonly used ionization source in mass spectrometry is electron-impact (EI) ionization source with electrons impacting to analyte with an energy of 70 eV. The kinetic energy of 70 eV is much higher than the ionization energy of organic molecules, and the ionization process approaches the maximal ionization efficiency. Thus, a large number of fragment peaks are usually observed in an EI mass spectrum. These fragments act as fingerprints of molecules, which can be used for identification of unknown molecules by searching EI-MS library, for example NIST Mass Spectral Library. This statistically based identification is particularly convenient and effective when analyzing a single component, for example a preseparated analyte by GC. However, there are many cases that analytes cannot be preseparated, for example very active components in a reaction, or fast on-line observation of evolving analytes. Consequently, the extensive fragmentation by EI-MS turns to a severe disadvantage: if each compound of a mixture produces a certain amount of fragment peaks, serious interference can be made, which will bring muscular obstacles to peak assignment. The best strategy is to use a “soft” ionization source with high selectivity. Here, “soft” means fragment-free or fragment-controllable.
关键词： SPI,Photoionization,APPI,REMPI,VUV Lamps,Synchrotron Radiation,Lasers,Mass Spectrometry
更新于2025-09-10 09:29:36