Effect of Basicity and Structure on the Hydration of Protonated Molecules, Proton-Bound Dimer and Cluster Formation: An Ion Mobility-Time of Flight Mass Spectrometry and Theoretical Study

Valadbeigi, Younes; Ilbeigi, Vahideh; Michalczuk, Bartosz; Sabo, Martin; Matejčík, Štefan

doi:10.1007/s13361-019-02180-z

Cited by 15 publications

(15 citation statements)

References 46 publications

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“…Because of the presence of some water vapor in the IMS cell (30–50 ppm), , the ions are usually hydrated. Hence, the hydration of ions should be considered during the proton transfer reaction To investigate effect of hydration on the ionization mechanism, hydration of CA.H + and NH 4 + was investigated theoretically.…”

Section: Resultsmentioning

confidence: 99%

A Novel Application of Dopants in Ion Mobility Spectrometry: Suppression of Fragment Ions of Citric Acid

2020

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Ion mobility spectra of citric acid (CA) are complex, and several peaks are observed for CA and its fragments in both the positive and negative modes. Using DFT calculations, we found that the fragments are both less acidic and less basic than CA in gas phase. Hence, we used a strong base, NH3, in positive mode to produce NH4 + as an alternative reactant ion (RI) and prevent protonation of the fragments. In the presence of NH4 +, only one peak for CA was observed because of its higher proton affinity (873 kJ mol–1) compared to NH3 (854 kJ mol–1). In the negative mode, CHCl3, CHBr3, and CHI3 were used as dopant gases to produce Cl–, Br–, and I– as RIs. These halides have less basicity than the common RIs in negative mode (NO2 –, NO3 –, O2 –) and selectively deprotonated CA in the presence of its fragments. Hence, using dopants with appropriate basicity, we could suppress the fragment peaks and obtain a plain IMS spectrum for CA containing only one peak in both the positive and negative modes. Using NH3 and CHCl3 dopants, the amount of CA in fresh lemon juice was determined as 39.5–42 g L–1 by direct injection without any purification. The effect of hydration of the reactant and product ions on the ionization mechanism in both negative and positive modes was investigated theoretically.

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Section: Resultsmentioning

confidence: 99%

A Novel Application of Dopants in Ion Mobility Spectrometry: Suppression of Fragment Ions of Citric Acid

2020

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“…Consequently, the hydrated ion clusters travel along the drift tube as a hydration-dehydration equilibrium mixture. Because the hydration and dehydration processes occur in the order of 10 −7 s, only one single peak can be observed in the IMS spectrum for ion clusters of different degrees of hydration [9,10]. Today, drift tube IMS is routinely coupled to gas chromatography (GC-IMS) as pre-separation to reduce asymmetric ion clustering (ion clusters of different analyte molecules) and to increase selectivity for compounds with highly similar product ions [11].…”

Section: Introductionmentioning

confidence: 99%

Nitrogen monoxide as dopant for enhanced selectivity of isomeric monoterpenes in drift tube ion mobility spectrometry with 3H ionization

2021

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The ion mobility spectra of the isomeric monoterpenes α-pinene, β-pinene, myrcene, and limonene in drift tube ion mobility spectrometry (IMS) with 3H radioactive ionization are highly similar and difficult to distinguish. The aim of this work was to enhance the selectivity of IMS by the addition of nitrogen monoxide (NO) as dopant and to investigate the underlying changes in ion formation responsible for the modified ion signals observed in the ion mobility spectra. Even though 3H-based-IMS systems have been used in hyphenation with gas chromatography (GC) for profiling of volatile organic compounds (VOCs), the investigation of ion formation still remains challenging and was exemplified by the investigated monoterpenes. Nonetheless, the formation of monomeric, dimeric, and trimeric ion clusters could be tentatively confirmed by a mass-to-mobility correlation and the highly similar pattern of ion signals in the monomer region was attributed to isomerization mechanisms potentially occurring after proton transfer reactions. The addition of NO as dopant could finally lead to the formation of additional product ions and increased the selectivity of IMS for the investigated monoterpenes as confirmed by principal component analysis (PCA). The discrimination of monoterpenes in the volatile profile is highly relevant in the quality control of hops and was given as the example for application. The results indicate that additional product ions were obtained by the formation of NO+ adduct ions, next to hydride abstraction, charge transfer, or fragmentation reactions. This approach can potentially leverage selectivity issues in VOC profiling of complex matrices, such as food matrices or raw materials in combination with chemometric pattern recognition techniques. Graphical abstract

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“…Ion mobility spectrometry (IMS) is a rapid and simple technique used for the analysis of a wide range of compounds 1–7 and investigation of ion formation in the gas phase 8–13 . In drift tube ion mobility spectrometers, ions are formed in the ion source, they move toward the detector under an electric field and are separated based on the difference in their mobility ( K o ) 14,15 .…”

Section: Introductionmentioning

confidence: 99%

Using gas‐phase chloride attachment for selective detection of morphine in a morphine/codeine mixture by ion mobility spectrometry

Valadbeigi

Ilbeigi

2021

Rapid Comm Mass Spectrometry

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Rationale Morphine and codeine are two important compounds of the opiate family that have vast applications in medicine. Several techniques have been reported for the determination of these opiates. Although ion mobility spectrometry (IMS) in positive ion mode can be applied for detection of both morphine and codeine, this technique on its own cannot detect a mixture of these two compounds because of the overlapping of their peaks. Methods An IMS instrument equipped with a corona discharge ion source operating in negative ion mode was used for the detection of anionic clusters of morphine and codeine. In normal negative ion mode, NOx−, CO3−, and On− act as the main reactant ions (RIs) which can deprotonate the analytes. We also used chloroform as a dopant to produce Cl− as an alternative RI. Results Morphine has a phenolic and an alcoholic OH group, while codeine bears only an alcoholic OH group. Because the phenolic OH group is more acidic, only morphine is deprotonated in negative ion mode in a morphine/codeine mixture. Furthermore, since morphine has two OH groups that can act as hydrogen‐bond donors, it acts as an anion receptor. Hence, in the presence of chloroform where Cl− acts as the RI, morphine traps the Cl− anion to form a morphine–Cl− (Mor.Cl−) adduct ion, while because of its structure codeine does not have this capability. Conclusions Using the difference in the structures of morphine and codeine, two ionization methods were proposed for selective detection of morphine. Morphine is more acidic than codeine and has greater anion‐receiving capability than codeine. Hence, it can both be deprotonated and form a adduct anion with Cl−. The Cl− attachment method is recommended for measurements at ambient temperature.

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Effect of Basicity and Structure on the Hydration of Protonated Molecules, Proton-Bound Dimer and Cluster Formation: An Ion Mobility-Time of Flight Mass Spectrometry and Theoretical Study

Cited by 15 publications

References 46 publications

A Novel Application of Dopants in Ion Mobility Spectrometry: Suppression of Fragment Ions of Citric Acid

A Novel Application of Dopants in Ion Mobility Spectrometry: Suppression of Fragment Ions of Citric Acid

Nitrogen monoxide as dopant for enhanced selectivity of isomeric monoterpenes in drift tube ion mobility spectrometry with 3H ionization

Using gas‐phase chloride attachment for selective detection of morphine in a morphine/codeine mixture by ion mobility spectrometry

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