Characterizing ion mobility and collision cross section of fatty acids using electrospray ion mobility mass spectrometry

Abstract

This study investigated the ion mobility (IM) and the collision cross section (CCS) of fatty acids (FAs) using electrospray IM MS. The IM analysis of 18 FA ions showed intriguing differences among the saturated FAs, monounsaturated FAs, multi-unsaturated FAs, and cis-isomer/trans-isomer with respect to the aliphatic tail chains. The length of aliphatic tail chain present in the ion structures had a strong influence on the differentiation of drift, while the number of double bond showed a weaker influence. The tiny drift differences between cis-isomer and trans-isomer were also observed. In the CCS measurements, two internal standards were involved in the mobility calibration and accuracy estimation. It insured our empirical CCS values were of high experimental precision (±0.35% or better) and accuracy (±0.25% or better). Moreover, the mass-to-charge ratio (m/z) - mobility plots obtained by ion mobility spectrometry with mass spectrometry analysis of FAs - was used to investigate the structural relationship between the molecules. Each series of FAs sharing a similar structure was aligned in the linear plot. Finally, the developed procedure was applied to the determination of FAs in rat adipose tissues, and it allowed the presence of 13 FAs to be confirmed with their exact masses and CCS values. These studies reveal the direct relationship between the behaviors in IM and the molecular structures and thus may provide further validations to the FA identification process.

Experimental and Theoretical Investigation of Sodiated Multimers of Steroid Epimers with Ion Mobility-Mass Spectrometry

“…Additionally, IM-MS offers great potential in rapid separation of isomers that cannot be resolved with mass spectrometry alone. First demonstrated for structural isomers of polycyclic aromatic hydrocarbons [15], this potential has been shown across numerous classes of biological molecules including carbohydrates [16–24], peptides [25, 26], oligonucleotides [19], lipids [19, 27–29], amino acids [29–31], fatty acids [32], glycans and glycopeptides [33], and other small molecules [34]. However, diastereomers and especially epimers, which differ in stereochemistry at a single chiral center, have very subtle structural differences that may contribute to only minor variation in CCS.…”

Study of short-lived and early reaction intermediates in organocatalytic asymmetric amination reactions by ion-mobility mass spectrometry

“…23,24 When using IM-MS, isomer species of intermediates with the same m/z can be resolved quickly and efficiently due to different drift time ( Figure 1). [25][26][27][28][29][30][31][32][33][34] Furthermore, the collision cross-section (CCS) value closely related to the size of ions could be measured based on drift time. By comparing with the theoretical CCS value, the structure identification would be more accurate.…”

Behaviors of Leucine and Isoleucine in Ion Mobility‐Quadrupole Time of Flight Mass Spectrometry

“…In this study, the experimental CCSs of leucine's protomers were measured referring to a reported method. [22] The computational process was done using a CCS calculator supported by Agilent IM Browsing software. Meanwhile, the theoretical CCSs were calculated based on the density functional theory.…”

“…[12][13][14][15] Moreover, the collision cross section (CCS) can be calculated from IM, which is the size parameter related to the averaged momentum transfer impact area of a molecule. [16,17] It acquires many reliable results in the structural chemistry study [18][19][20][21][22] and intermediate study. [23] When a molecule is ionized in an MS ion source, protomers caused by the multi-protonation sites are often discovered.…”