Electrospray Ionization High-Resolution Ion Mobility Spectrometry for the Detection of Organic Compounds, 1. Amino Acids

Abstract

Our aim in this investigation was to demonstrate the potential of the high-resolution electrospray ionization ion mobility spectrometry (ESI-IMS) technique as an analytical separation tool in analyzing biomolecular mixtures to pursue astrobiological objectives of searching for the chemical signatures of life during an in-situ exploration of solar system bodies. Because amino acids represent the basic building blocks of life, we used common amino acids to conduct the first part of our investigation, which is being reported here, to demonstrate the feasibility of using the ESI-IMS technique for detection of the chemical signatures of life. The ion mobilities of common amino acids were determined by electrospray ionization ion mobility spectrometry using three different drift gases (N2, Ar, and CO2). We demonstrated that the selectivity can be vastly improved in ion mobility spectroscopy (IMS) in detecting organic molecules by using different drift gases. When a judicial choice of drift gas is made, a vastly improved separation of two different amino acid ions resulted. It was found that each of the studied amino acids could be uniquely identified from the others, with the exception of alanine and glycine, which were never separable by more then 0.1 ms. This unique identification is a result of the different polarizabilities of the various drift gases. In addition, a better separation was achieved by changing the drift voltage in successive experimental runs without significantly degrading the resolution. We also report the result of our analysis of liquid samples containing mixtures of amino acids.

Collision Cross Sections for 20 Protonated Amino Acids: Fourier Transform Ion Cyclotron Resonance and Ion Mobility Results

“…The resulting cross sections for these lowest-energy conformers were then weighted using a 300 K Boltzmann distribution function and averaged. We justify this averaging by noting that none of the techniques used for experimentally measuring the cross sections have sufficient resolution to resolve the different conformers that may be present for a given amino acid; in particular, the experimental arrival time distributions in the literature [4,5] show single peaks for each amino acid. A similar averaging approach has been used previously [7].…”

“…The mobilities of the protonated biogenic amino acid ions have been reported at least three times [4][5][6], and cross sections for an abbreviated set examined using traveling wave ion mobility spectrometry (TWIMS) have also been reported [7]. Mobilities for a set of abiogenic amino acids, which showed a correlation between molecular weight and mobility, have also appeared [8].…”

Computational fluid dynamics-Monte Carlo method for calculation of the ion trajectories and applications in ion mobility spectrometry

“…The mass of background gas particle was set as 28.9 amu. The polarizability of the carriergas molecule for the dry air was approximated as 1.73Å 3 [64]. The distribution of (DMMP)H + and (H 2 O) 3 H + ions at different observation times was show in Fig.…”

Multidimensional Separation of Natural Products Using Liquid Chromatography Coupled to Hadamard Transform Ion Mobility Mass Spectrometry

“…We selected amino acids and capsaicinoids to compare their trend line [58,59]. Nineteen free amino acids were detected with HPLC-IMMS in mass-and retention timeselected ion mobility spectra.…”