Buffer gas modifiers effect resolution in ion mobility spectrometry through selective ion‐molecule clustering reactions

Abstract

RATIONALE When polar molecules (modifiers) are introduced into the buffer gas of an ion mobility spectrometer, most ion mobilities decrease due to the formation of ion-modifier clusters. METHODS We used ethyl lactate, nitrobenzene, 2-butanol, and tetrahydrofuran-2-carbonitrile as buffer gas modifiers and electrospray ionization ion mobility spectrometry (IMS) coupled to quadrupole mass spectrometry. Ethyl lactate, nitrobenzene, and tetrahydrofuran-2-carbonitrile had not been tested as buffer gas modifiers and 2-butanol had not been used with basic amino acids. RESULTS The ion mobilities of several diamines (arginine, histidine, lysine, and atenolol) were not affected or only slightly reduced when these modifiers were introduced into the buffer gas (3.4% average reduction in an analyte's mobility for the three modifiers). Intramolecular bridges caused limited change in the ion mobilities of diamines when modifiers were added to the buffer gas; these bridges hindered the attachment of modifier molecules to the positive charge of ions and delocalized the charge, which deterred clustering. There was also a tendency towards large changes in ion mobility when the mass of the analyte decreased; ethanolamine, the smallest compound tested, had the largest reduction in ion mobility with the introduction of modifiers into the buffer gas (61%). These differences in mobilities, together with the lack of shift in bridge-forming ions, were used to separate ions that overlapped in IMS, such as isoleucine and lysine, and arginine and phenylalanine, and made possible the prediction of separation or not of overlapping ions. CONCLUSIONS The introduction of modifiers into the buffer gas in IMS can selectively alter the mobilities of analytes to aid in compound identification and/or enable the separation of overlapping analyte peaks.

Review on Ion Mobility Spectrometry. Part 2: hyphenated methods and effects of experimental parameters

“…Fernández-Maestre et al . 131, 132 have studied how the buffered gas modifiers affect resolution in ion mobility spectrometry through selective ion-molecule clustering reactions. Shvartsburg et al .…”

Dopants and gas modifiers in ion mobility spectrometry

“…Information on dopants and modifiers applications in order to detect different analytes with DT-IMS and DMS are summarized in Table 3. sulfur hexafluoride, nitrogen oxides [80] acetone positive control of proton transfer CWA [47] gas modifiers for DT-IMS chiral modifiers: S-(+)-2-butanol R-(-)-2-butanol positive changing of collision cross-section for ions moving in drift section, analyte-modifier cluster formation stereoisomers [90] ketones, e.g., 5-nonanone positive analyte-modifier cluster formation separation of hydrazines and ammonia [38] ammonia positive analyte-modifier cluster formation separation of amine derivatives, and 2,4-lutidine [28] nitrobenzene positive analyte-modifier cluster formation separation of amine derivatives [92,93] ethyl lactate positive analyte-modifier cluster formation separation of atenolol, arginine, histidine, lysine, caffeine, and glucosamine [91,92] methanol positive analyte-modifier cluster formation separation of TTEA, asparagine, and valine [94] gas modifiers for DMS polar modiefiers, e.g., isopropanol, methanol, acetone positive negative clustering-declustering control many different compounds, increasing peak capacity [97][98][99][100] isopropanol, 1-butanol, ethyl acetate positive clustering-declustering control DNA damage markers [101] alcohols, acetone, acetonitrile, positive clustering-declustering control separation of drugs and metabolites [102] benzene (nonpolar modifier) positive - modifier-to-analyte interaction improvement in the sensitivity and selectivity of DMS for detection of aromatic compounds [106] …”

“…Ketone vapors were introduced into the drift gas to separate ammonia from hydrazine [38]. The best separation was obtained when 5- carbonitrile, have also been studied [92]. Introducing the modifier vapors to the buffer gas resulted in ion-modifier clusters formation.…”

Chiral detection of entecavir stereoisomeric impurities through coordination with R‐besivance and ZnII using mass spectrometry

“…It is clear that MS possesses advantages such as rapid analysis, high sensitivity, and reduced sample consumption; it also does not necessitate isotope labeling or other derivatization treatment to analytes. Currently, there are 4 major types of MS techniques used in chiral recognition: (1) the host‐guest method, (2) ion/molecule (equilibrium) reactions, (3) collision‐induced dissociation of diastereomeric complex (which includes the kinetic method [KM], the fixed ligand KM, and the chiral recognition ratio method) and (4) ion mobility MS . The most commonly used type is KM because the experimental data interpretation is much easier because only the relative abundances of 2 fragment ions are needed and isomer separation is not necessary.…”