scholarly journals Evidence of Reactivity in the Membrane for the Unstable Monochloramine during MIMS Analysis

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4252 ◽  
Author(s):  
Essyllt Louarn ◽  
Abdoul. Monem Asri-Idlibi ◽  
Julien Leprovost ◽  
Michel Héninger ◽  
Hélène Mestdagh
Keyword(s):  
Mass Spectrometry ◽  
Proton Affinity ◽  
Chemical Ionization ◽  
Low Pressure ◽  
Solution Concentration ◽  
Ammonia Molecule ◽  
Water Molecules ◽  
Basic Form ◽  
Membrane Inlet Mass Spectrometry ◽  
Unstable Molecules

Membrane Inlet Mass Spectrometry (MIMS) was used to analyze monochloramine solutions (NH2Cl) and ammonia solutions in a compact FTICR. Chemical ionization enables identification and quantification of the products present in the permeate. The responses of protonated monochloramine and ammonium increase linearly with the solution concentration. The enrichments were respectively 1.2 and 5.5. Pervaporation is dependent on pH and only the basic form of ammonia NH3 pervaporates through the membrane. Unexpectedly, the small ammonia molecule permeated very slowly. It could be due to interactions with water molecules inside the membrane that create clusters. Moreover, NH2Cl solutions, in addition to the NH3Cl+ signal, presented a strong NH4+ signal at m/z 18.034. Ammonia presence in the low-pressure zone before ionization is probable as NH4+ was detected with all the precursors used, particularly CF3+ and trimethylbenzene that presents a proton affinity higher than monochloramine. Ammonia may be formed inside the membrane due to the fact that NH2Cl is unstable and may react with the water present in the membrane. Those results highlight the need for caution when dealing with chloramines in MIMS and more generally with unstable molecules.

scholarly journals Evidence of Reactivity in the Membrane for the Unstable Monochloramine during MIMS Analysis

2018 ◽  
Author(s):  
Essyllt Louarn ◽  
A. Monem Adli-Idlibi ◽  
Julien Leprovost ◽  
Michel Héninger ◽  
Hélène Mestdagh
Keyword(s):  
Mass Spectrometry ◽  
Proton Affinity ◽  
Chemical Ionization ◽  
Low Pressure ◽  
Solution Concentration ◽  
Ammonia Molecule ◽  
Water Molecules ◽  
Basic Form ◽  
Membrane Inlet Mass Spectrometry ◽  
Unstable Molecules

Membrane Inlet Mass Spectrometry (MIMS) was used to analyze monochloramine solutions (NH2Cl) and ammonia solutions in a compact FTICR. Chemical ionization enables identification and quantification of the products present in the permeate. The responses of protonated monochloramine and ammonium increase linearly with the solution concentration. The enrichments were respectively 1.2 and 5.5. Pervaporation is dependent on pH and only the basic form of ammonia NH3 pervaporates through the membrane. Unexpectedly, the small ammonia molecule permeated very slowly. It could be due to interactions with water molecules inside the membrane that create clusters. Moreover, NH2Cl solutions, in addition to the NH3Cl+ signal, presented a strong NH4+ signal at m/z 18.034 . Ammonia presence in the low-pressure zone before ionization is probable as NH4+ was detected with all the precursors used, particularly CF3+ and trimethylbenzene that presents a proton affinity higher than monochloramine. Ammonia may be formed inside the membrane due to the fact that NH2Cl is unstable and may react with the water present in the membrane. Those results highlight the need for caution when dealing with chloramines in MIMS and more generally with unstable molecules.

scholarly journals Performance of a new coaxial ion–molecule reaction region for low-pressure chemical ionization mass spectrometry with reduced instrument wall interactions

2019 ◽  
Vol 12 (11) ◽  
pp. 5829-5844 ◽  
Author(s):  
Brett B. Palm ◽  
Xiaoxi Liu ◽  
Jose L. Jimenez ◽  
Joel A. Thornton
Keyword(s):  
Mass Spectrometry ◽  
Chemical Ionization ◽  
Reaction Times ◽  
Low Pressure ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Molecule Reaction ◽  
Measurement Protocol ◽  
Wall Interactions

Abstract. Chemical ionization mass spectrometry (CIMS) techniques have become prominent methods for sampling trace gases of relatively low volatility. Such gases are often referred to as being “sticky”, i.e., having measurement artifacts due to interactions between analyte molecules and instrument walls, given their tendency to interact with wall surfaces via absorption or adsorption processes. These surface interactions can impact the precision, accuracy, and detection limits of the measurements. We introduce a low-pressure ion–molecule reaction (IMR) region primarily built for performing iodide-adduct ionization, though other adduct ionization schemes could be employed. The design goals were to improve upon previous low-pressure IMR versions by reducing impacts of wall interactions at low pressure while maintaining sufficient ion–molecule reaction times. Chamber measurements demonstrate that the IMR delay times (i.e., magnitude of wall interactions) for a range of organic molecules spanning 5 orders of magnitude in volatility are 3 to 10 times lower in the new IMR compared to previous versions. Despite these improvements, wall interactions are still present and need to be understood. To that end, we also introduce a conceptual framework for considering instrument wall interactions and a measurement protocol to accurately capture the time dependence of analyte concentrations. This protocol uses short-duration, high-frequency measurements of the total background (i.e., fast zeros) during ambient measurements as well as during calibration factor determinations. This framework and associated terminology applies to any instrument and ionization technique that samples compounds susceptible to wall interactions.

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