MS/MS studies on the selective on-line detection of sesquiterpenes using a Flowing Afterglow-Tandem Mass Spectrometer (FA-TMS)

A Flowing Afterglow-Tandem Mass Spectrometer (FA-TMS) was used to investigate the feasibility of selective on-line detection of a series of seven sesquiterpenes (SQTs). These SQTs were chemically ionized by either H3O+ or NO+ reagent ions in the FA, resulting among others in protonated SQT and SQT molecular ions, respectively. These and other Chemical Ionization (CI) product ions were subsequently subjected to dissociation by collisions with Ar atoms in the collision cell of the tandem mass spectrometer. The fragmentation spectra show similarities with mass spectra obtained for these compounds with other instruments such as a Proton Transfer Reaction-Linear Ion Trap (PTR-LIT), a Proton Transfer Reaction-Mass Spectrometer (PTR-MS), a Triple Quadrupole-Mass Spectrometer (QqQ-MS) and a Selected Ion Flow Tube-Mass Spectrometer (SIFT-MS). Fragmentation of protonated SQT is characterized by fragment ions at the same masses but with different intensities for the individual SQT. Distinction of SQTs is based on well-chosen intensity ratios and collision energies. The fragmentation patterns of SQT molecular ions show specific fragment ion tracers at m/z 119, m/z 162, m/z 137 and m/z 131 for alpha-cedrene, delta-neoclovene, isolongifolene and alpha-humulene, respectively. Consequently, chemical ionization of SQT by NO+, followed by MS/MS of SQT(+) seems to open a way for selective quantification of SQTs in mixtures

Unsupervised system to classify SO2 pollutant concentrations in Salamanca, Mexico

Salamanca is cataloged as one of the most polluted cities in Mexico. In order to observe the behavior and clarify the influence of wind parameters on the Sulphur Dioxide (SO2) concentrations a Self-Organizing Maps (SOM) Neural Network have been implemented at three monitoring locations for the period from January 1 to December 31, 2006. The maximum and minimum daily values of SO2 concentrations measured during the year of 2006 were correlated with the wind parameters of the same period. The main advantages of the SOM Neural Network is that it allows to integrate data from different sensors and provide readily interpretation results. Especially, it is powerful mapping and classification tool, which others information in an easier way and facilitates the task of establishing an order of priority between the distinguished groups of concentrations depending on their need for further research or remediation actions in subsequent management steps. For each monitoring location, SOM classifications were evaluated with respect to pollution levels established by Health Authorities. The classification system can help to establish a better air quality monitoring methodology that is essential for assessing the effectiveness of imposed pollution controls, strategies, and facilitate the pollutants reduction

PM₁₀ air quality variations in an urbanized and industrialized harbor

In this paper we investigate the PM10 pollution episodes associated with meteorological situations in an urban and industrialized coastal site of the southern part of the North Sea, representative of a typical harbor for trade. In a first part, the spatio-temporal variability of PM10, SO2, NOx and O3 concentrations at the urban scale suggests that both regional air masses and local emissions affect harbor's pollution. In a second part, hierarchical clustering analysis (HCA) performed on meteorological data and PM10 concentrations reveals two main air quality (AQ) regimes. The first one is related to low PM10 levels, which occur under low-pressure conditions due to meteorological conditions favoring a good dispersion of pollutants. The second one is characterized by higher PM10 concentrations appearing under high-pressure conditions. The highest polluted days are characterized by the highest temperatures and hardly any rain. These pollution episodes predominantly occur during sea breeze days, but also as the result of occasional industrial releases. The HCA proved to be an appropriate method to define AQ regimes and to identify meteorological conditions favoring or not PM pollution episodes in Dunkerque conurbatio

Flowing afterglow selected ion flow tube (FA-SIFT) study of ion/molecule reactions in support of the detection of biogenic alcohols by medium-pressure chemical ionization mass spectrometry techniques

This article deals with the validation of and first measurements with a newly constructed flowing afterglow selected ion flow tube (FA-SIFT) instrument. All reactions were studied in He buffer gas at a pressure of 1.43 hPa and a temperature of 298 K. The validation consisted of the study of the gas-phase ion/molecule reactions of methanol and ethanol (M) with the reactant ions H3O+·(H2O)n (n = 0–3), MH+, M2H+, and MH+·H2O and the reactions of MH+ with H2O. Obtained results are compared with available literature data and with calculated collision rate constants. The validated FA-SIFT has subsequently been used to characterize the reactions of the unsaturated biogenic alcohols 2-methyl-3-buten-2-ol, 1-penten-3-ol, cis-3-hexen-1-ol and trans-2-hexen-1-ol (ROH) with H3O+·(H2O)n (n = 0–3) as well as the secondary reactions of the H3O+/ROH product ions with H2O (hydration) and ROH in view of their accurate quantification in ambient air samples with medium-pressure chemical ionization mass spectrometry (CIMS) instrumentation using H3O+ reactant ions. Whereas water elimination following proton transfer was found to be the main mechanism for all H3O+/ROH reactions studied and for the H3O+·H2O/trans-2-hexen-1-ol reaction, all other H3O+·(H2O)n/ROH (n = 1, 2) reactions proceeded by multiple reaction mechanisms. H3O+·(H2O)3 reactions proceeded mainly (C6 alcohols) or exclusively (C5 alcohols) by ligand switching followed by water elimination. Hydration of the H3O+/ROH product ions was observed whenever they contained oxygen. The secondary reactions with ROH were also found to proceed by multiple reaction pathways

MS/MS studies on the selective on-line detection of sesquiterpenes using a Flowing Afterglow–Tandem Mass Spectrometer (FA-TMS)

A Flowing Afterglow-Tandem Mass Spectrometer (FA-TMS) was used to investigate the feasibility of selective on-line detection of a series of seven sesquiterpenes (SQTs). These SQTs were chemically ionized by either H<sub>3</sub>O<sup>+</sup> or NO<sup>+</sup> reagent ions in the FA, resulting among others in protonated SQT and SQT molecular ions, respectively. These and other Chemical Ionization (CI) product ions were subsequently subjected to dissociation by collisions with Ar atoms in the collision cell of the tandem mass spectrometer. The fragmentation spectra show similarities with mass spectra obtained for these compounds with other instruments such as a Proton Transfer Reaction-Linear Ion Trap (PTR-LIT), a Proton Transfer Reaction-Mass Spectrometer (PTR-MS), a Triple Quadrupole-Mass Spectrometer (QqQ-MS) and a Selected Ion Flow Tube-Mass Spectrometer (SIFT-MS). Fragmentation of protonated SQT is characterized by fragment ions at the same masses but with different intensities for the individual SQT. Distinction of SQTs is based on well-chosen intensity ratios and collision energies. The fragmentation patterns of SQT molecular ions show specific fragment ion tracers at <i>m/z</i> 119, <i>m/z</i>162, <i>m/z</i> 137 and <i>m/z</i> 131 for α-cedrene, δ-neoclovene, isolongifolene and α-humulene, respectively. Consequently, chemical ionization of SQT by NO<sup>+</sup>, followed by MS/MS of SQT<sup>+</sup> seems to open a way for selective quantification of SQTs in mixtures