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Determinative Techniques to Measure Organics and Inorganics
Published in Paul R. Loconto, Trace Environmental Quantitative Analysis, 2020
It is the application of Selected Ion Flow Tube-Mass Spectrometry (SIFT-MS)! Recall that near the end of Chapter 3, the topic of conventional sample preparation techniques available for sampling air pollutants was introduced. These techniques are still quite valuable and routinely used. SIFT-MS however, holds the promise of direct air sampling combined with direct quantitative analysis via quadrupole mass spectrometry, without the need for sample prep! This discussion on SIFT-MS is largely drawn from a recent book that was brought to the author’s attention.135 SIFT-MS originated in the pioneering work of Spanel and Smith in 1996 which followed from selected ion tube flow tube (SIFT) technology introduced 20 years ago by Adams and Smith. SIFT, in turn, was an extension of the early work of adapting flow tubes to investigate ion-molecule reactions begun in the late 1960s by Ferguson and collaborators. SIFT-MS is unique in that the reagent (or precursor) ions are well characterized and are mass-selected, and undergo known ion-molecule reactions with the analytes. In principle, an analyte such as an air pollutant can be quantitated without the need for analyte calibration!
Insight into Knapsack Metabolite Ecology Database: A Comprehensive Source of Species: Voc-Biological Activity Relationships
Published in Raquel Cumeras, Xavier Correig, Volatile organic compound analysis in biomedical diagnosis applications, 2018
Azian Azamimi Abdullah, M.D. Altaf-Ul-Amin, Shigehiko Kanaya
Advancement in analytical methods such as gas chromatography-mass spectrometry (GC-MS), proton transfer reaction mass spectrometry (PTR-MS) and selected ion flow tube mass spectrometry (SIFT-MS) have provided an opportunity to identify the volatile metabolites of living organisms in research laboratories. These analytical approaches generate a large amount of data and require specialized mathematical, statistical and bioinformatics tools to analyze such data. Despite the advances in sampling and detection by these analytical methods, only a few databases have been developed to handle these large and complex datasets. There are some VOC databases, which can be accessed freely. However, their applicability is often limited by several elements. Most of these databases only focus on volatiles, which are emitted by certain living organisms and have limited applications. None of these databases provide information on biological activities of VOCs and species-species interaction based on volatiles. To meet this purpose, we have developed a VOC database of microorganisms, fungi, and plants as well as human being, which comprises the relation between emitting species, volatiles and their biological activities (Abdullah et al., 2015). We have deposited the VOC data into KNApSAcK Metabolite Ecology Database, and this database is currently available at http://kanaya.naist.jp/MetaboliteEcology/top.jsp. Also, the database can be accessed online by clicking the corresponding button in the main window (Figure 9.1). Apart from the database development, we also analyzed the VOC data using hierarchical clustering and network clustering based on DPClus algorithm. In addition, we also performed the heatmap clustering based on Tanimoto coefficient as the similarity index between chemical structures to cluster all VOCs emitted by various biological species to understand the relationships between chemical structures of VOCs and their biological activities.
V-shaped ion funnel proton transfer reaction mass spectrometry
Published in Instrumentation Science & Technology, 2019
Yujie Wang, Kexiu Dong, Yannan Chu
Figure 2a shows that the protonated water clusters are quickly broken by collisions at higher RF voltages with fixed DC voltage and RF frequency. The effect of RF voltage on the protonated water clusters is similar to that of the E/N in the DC-only electric field.[20] Therefore, the water-cluster ion signals are greatly reduced at high collisional energies. However, the experimental conditions in the V-shaped IF PTR-MS are dominated by the variation of the NO+ signal. Different from the reported U-shaped IF PTR-MS,[13] the NO+ signal grows significantly as RF voltage increases (Figure 2a). This phenomenon may occur because of charge transfer reaction between H2O+ (12.6 eV ionization energy[24]) and NO (9.3 eV ionization energy). In a selected ion flow tube mass spectrometry study,[25] H3O+ with high initial energies may collide with buffer gas producing H2O+. The significant NO+ signal intensity confirms that the collisions are more intense in V-shaped IF PTR-MS and further demonstrated by the subsequent ketone detection. Although the O2+ (12.1 eV ionization energy) signal intensity was negligible compared to H3O+, this phenomenon is a result of the improved ion transmission in the DC–RF electric field.