Experimental and theoretical investigation into the correlation between mass and ion mobility for choline and other ammonium cations in N2

Hyungjun Kim, Hugh I. Kim, Paul V. Johnson, Luther W. Beegle, J. L. Beauchamp, William A. Goddard, Isik Kanik

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A number of tertiary amine and quaternary ammonium cations spanning a mass range of 60-146 amu (trimethylamine, tetramethylammonium, trimethylethylaminonium, N,N-dimethylaminoethanol, choline, N,N-dimethylglycine, betaine, acetylcholine, (3-carboxypropyl)trimethylammonium) were investigated using electrospray ionization ion mobility spectrometry. Measured ion mobilities demonstrate a high correlation between mass and mobility in N2. In addition, identical mobilities within experimental uncertainties are observed for structurally dissimilar ions with similar ion masses. For example, dimethylethylammonium (88 amu) cations and protonated N,N-dimethylaminoethanol cations (90 amu) show identical mobilities (1.93 cm2 V-1 s-1) though N,N-dimethylaminoethanol contains a hydroxyl functional group while dimethylethylammonium only contains alkyl groups. Computational analysis was performed using the modified trajectory (TJ) method with nonspherical N2 molecules as the drift gas. The sensitivity of the ammonium cation collision cross sections to the details of the ion-neutral interactions was investigated and compared to other classes of organic molecules (carboxylic acids and abiotic amino acids). The specific charge distribution of the molecular ions in the investigated mass range has an insignificant affect on the collision cross section.

Original languageEnglish
Pages (from-to)1928-1936
Number of pages9
JournalAnalytical chemistry
Issue number6
Publication statusPublished - 2008 Mar 15
Externally publishedYes


ASJC Scopus subject areas

  • Analytical Chemistry

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