scholarly journals Ion-shift reagent binding energy and the shift-mass correlation in ion mobility spectrometry

Author(s):  
Roberto Fernandez-Maestre ◽  
Mahmoud Tabrizchi ◽  
Dairo Meza-Morelos

Ion mobility spectrometry is widely used for the detection of illegal substances and explosives in airports, ports, custom, some stations and many other important places. This task is usually complicated by false positives caused by overlapping the target peaks with that of interferents, commonly associated with samples of interest. Shift reagents (SR) are species that selectively change ion mobilities through adduction with analyte ions when they are introduced in IMS instruments. This characteristic can be used to discriminate false positives because the interferents and illegal substances respond differently to SR depending on the structure and size of analytes and their interaction energy with SR. This study demonstrates that ion mobility shifts upon introduction of SR depend, not only on the ion masses, but on the interaction energies of the ion:SR adducts. In this study, we introduced five different SRs using ESI-IMS-MS to study the effect of the interaction energy and size on mobility shifts. The mobility shifts showed a decreasing trend as the molecular weight increased for the series of compounds ethanolamine, valinol, serine, threonine, phenylalanine, tyrosine, tributylamine, tryptophan, desipramine, and tribenzylamine. It was proved that the decreasing trend was partially due to the inverse relation between the mobility and drift time and hence, the shift in drift time better reflects the pure effect of SR on the mobility of analytes. Yet the drift time shift exhibited a mild decrease with the mass of ions. Valinol pulled out from this trend because it had a low binding energy interaction with all the SR and, consequently, its clusters were short-lived. This short lifetime produced fewer collisions against the buffer gas and a drift time shorter compared to those of ions of similar molecular weight. Analyte ion:SR interactions were calculated using Gaussian. IMS with the introduction of SR could be the choice for the free-interferents detection of illegal drugs, explosives, and biological and warfare agents. The suppression of false positives could facilitate the transit of passengers and cargos, rise the confiscation of illicit substances, and save money and distresses due to needless delays. Keywords: Adduction, ion mobility spectrometry, mass spectrometry, shift reagent, valinol, buffer gas modifier

2021 ◽  
Author(s):  
Roberto Fernandez-Maestre ◽  
Markus Doerr

<p><a>Racemic mixtures of twelve common </a>a-amino acids and three chiral drugs were tested for the separation of their enantiomers by ion mobility spectrometry (IMS)-quadrupole mass spectrometry (MS). Separations were tested by introducing chiral selectors in the mobility spectrometer buffer gas. (R)-α-(trifluoromethyl) benzyl alcohol, (R)-tetrahydrofuran-2-carbonitrile, (L)-ethyl lactate, methyl (S)-2-chloropropionate, and the R and S enantiomers of 2-butanol and 1-phenyl ethanol were evaluated as chiral selectors. Experimental conditions were varied during the tests including buffer gas temperature, concentration, and type of chiral selectors, analyte concentration, electrospray voltage, electrospray (ESI) solvent pH, and buffer gas flow. The individual enantiomers yielded different drift times for periods of up to 8 hours in a few experiments; such drift times were sufficiently different (~ 0.3 ms) to partially resolve the enantiomers in racemic mixtures, but these mixtures always yielded a single mobility peak at the experimental conditions tested with a drift time similar to that of one of the enantiomers. Energy calculations of the chiral selector –ion interactions showed that these separations are unlikely using 2-butanol as chiral selector but they might be feasible depending on the nature of chiral selectors and the type of enantiomers.</p>


2021 ◽  
Author(s):  
Roberto Fernandez-Maestre ◽  
Markus Doerr

<p><a>Racemic mixtures of twelve common </a>a-amino acids and three chiral drugs were tested for the separation of their enantiomers by ion mobility spectrometry (IMS)-quadrupole mass spectrometry (MS). Separations were tested by introducing chiral selectors in the mobility spectrometer buffer gas. (R)-α-(trifluoromethyl) benzyl alcohol, (R)-tetrahydrofuran-2-carbonitrile, (L)-ethyl lactate, methyl (S)-2-chloropropionate, and the R and S enantiomers of 2-butanol and 1-phenyl ethanol were evaluated as chiral selectors. Experimental conditions were varied during the tests including buffer gas temperature, concentration, and type of chiral selectors, analyte concentration, electrospray voltage, electrospray (ESI) solvent pH, and buffer gas flow. The individual enantiomers yielded different drift times for periods of up to 8 hours in a few experiments; such drift times were sufficiently different (~ 0.3 ms) to partially resolve the enantiomers in racemic mixtures, but these mixtures always yielded a single mobility peak at the experimental conditions tested with a drift time similar to that of one of the enantiomers. Energy calculations of the chiral selector –ion interactions showed that these separations are unlikely using 2-butanol as chiral selector but they might be feasible depending on the nature of chiral selectors and the type of enantiomers.</p>


2017 ◽  
Vol 412 ◽  
pp. 20-25 ◽  
Author(s):  
Zahra Izadi ◽  
Mahmoud Tabrizchi ◽  
Hossein Farrokhpour

2018 ◽  
Author(s):  
Eleanor Sinclair ◽  
Katherine A. Hollywood ◽  
Cunyu Yan ◽  
Richard Blankley ◽  
Rainer Breitling ◽  
...  

<p>Chromatography based mass spectrometry approaches (xC-MS) are commonly used in untargeted metabolomics, providing retention time, m/z values and metabolite specific-fragments all of which are used to identify and validate an unknown analyte. Ion mobility-mass spectrometry (IM-MS) is emerging as an enhancement to classic xC-MS strategies, by offering additional separation as well as collision cross section (CCS) determination. In order to apply such an approach to a synthetic biology workflow, verified data from metabolite standards is necessary. In this work we present experimental <sup>DT</sup>CCS<sub>N2</sub> values for a range of metabolites in positive and negative ionisation modes using drift time-ion mobility-mass spectrometry (DT-IM-MS) with nitrogen as the buffer gas. Creating a useful database containing <sup>DT</sup>CCS<sub>N2</sub> measurements for application in metabolite identification relies on a robust technique that acquires measurements of high reproducibility. We report that 86% of the metabolites measured in replicate have a relative standard deviation lower than 0.2 %. Examples of metabolites with near identical mass are demonstrated to be separated by ion mobility with over 4% difference in <sup>DT</sup>CCS<sub>N2</sub> values. We conclude that the integration of ion mobility into current LC-MS workflows can aid in small molecule identification for both targeted and untargeted metabolite screening which is commonly performed in synthetic biology.</p>


2016 ◽  
Vol 30 (11) ◽  
pp. 1332-1338 ◽  
Author(s):  
Roberto Fernandez-Maestre ◽  
Dairo Meza-Morelos ◽  
Ching Wu

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