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Mass Spectrometric Analysis
Published in Adorjan Aszalos, Modern Analysis of Antibiotics, 2020
A promising method is being developed in which analytes are ionized by the buffer ions in solution [120]. The entire eluant (up to 2 ml/min) flows directly into the ion source as an aerosol. The droplets are desolvated, leaving the ions to diffuse to the sampling aperture, where they are transmitted to the mass analyzer. Although the method seems particularly applicable to compounds that are readily ionized in solution, it also has been successfully applied to neutral compounds. The efficiency of producing these ions seems nearly independent of the molecular weight and volatility of the analyte. The mass spectra obtained from this method are similar to those obtained by field desorption. A commercial variant uses an atmospheric pressure ionization source [121]. A variety of new methods and variations of the ones described here are being explored. At present there is no method that has been generally accepted and marketed for potential users. Applications of LC-MS to antibiotic research has been minimal [122,123] but is certain to increase as the method develops. The antibiotics that have been examined by combined LC-MS are listed in Table 1.
Mass spectrometry based metabolomics for small molecule metabolites mining and confirmation as potential biomarkers for schistosomiasis – case of the Okavango Delta communities in Botswana
Published in Expert Review of Proteomics, 2022
Sedireng M. Ndolo, Matshediso Zachariah, Lebotse Molefi, Nthabiseng Phaladze, Kwenga F. Sichilongo
Table 1 summarizes the instrumentation, methods, ionization modes, columns, data filtration, and statistical evaluation techniques that have been employed in schistosomiasis metabolomics involving separation science and mass spectrometry for small molecules. Table 1 also emphasizes that there is very little literature on the metabolomics of schistosomiasis using either LC-MS or GC-MS. This underscores the tag attached to this disease, i.e. ‘a neglected tropical disease,’ which is the case despite affecting over a quarter of a billion people globally. The most commonly used ionization mode is electrospray ionization (ESI) for LC-MS and electron ionization (EI) for GC-MS. Future studies could focus on interrogating other ionization techniques, such as atmospheric pressure chemical ionization (APCI). This is well suited for small-molecule ionization using LC-MS and soft ionization, such as field desorption, in addition to chemical ionization for GC-MS. These techniques need to be probed for the analysis of abundant metabolites during ionization. There is a need to explore other data filtration software packages, in addition to XCMS, in order to increase the chances of biomarker discovery. This applies to multivariate statistical tools that revolve around PCA and PLS-DA.