Linearized Equations for the Reduced Ion Mobilities of Polar Aliphatic Organic Compounds

Abstract

Over the years, ion mobility spectrometry has evolved into a powerful technique for rapid identification of analytes in very complex sample matrixes such as human breath. Every analyte detected has a characteristic ion mobility value (and a retention time when additional preseparation techniques are employed) which is used to identify the peaks in a spectrum either by comparison with reference analytes or by simultaneous mass spectrometric measurements. In this study, the mass-mobility correlations between compounds in three different homologous series are used to predict the mobilities of the other substances in the same series in a medium of synthetic air. The results show a very high accuracy (>99.5%) of the prognosis. The linear trend equations of ion mobilities, as a function of the number of carbon atoms, obtained from the different series were then generalized into one linear equation for the reduced ion mobility for the polar aliphatic compounds and is validated by comparing it with the traditional Mason-Schamp equation. To compare the empirical equation obtained from the prognosis and the Mason-Schamp equation, the collision integral term in the latter was split into two terms to linearize it. The resulting novel ion mobility equation could be the starting step to completely describe the relationship between ion collision integral and the ion mobility for polar aliphatic compounds. The splitting of the collision integral into two terms will also give new inputs to describe the various ion models and the different forces that act on the ions and the neutral gas molecules upon which the collision integral is dependent on. This prognosis method could, furthermore, be extended to all other classes of organic compounds and could serve as a useful tool for identification of unknowns in ion mobility spectra, thereby considerably reducing the time-consuming and costly reference measurements and other coupling techniques that are currently employed.

Structure of aldehyde cluster ions in the gas phase, according to data from ion mobility spectrometry and ab initio calculations

“…In [20], linear dependences 1/K 0 versus N(C) were obtained for alcohols, aldehydes, and ketones. Since the value of 1/K 0 is proportional to the collision cross section, the authors suggested that the collision cross section could be presented in the form of two components.…”

“…However, the above works are of an applied character and do not deal with questions of the structure of the formed ions. Considering homological series [20][21][22], which allows us to find correlations between the molecular weight and ionic mobility of organic compounds in the gas phase, is useful. In this work, the structure of ions of the monomers and dimers formed by aldehydes in the gas phase is investigated by means of ion mobility spectrometry in combination with ab initio quantum chemical calculations.…”

Computational Methods for Metabolomic Data Analysis of Ion Mobility Spectrometry Data—Reviewing the State of the Art

“…In this study they discovered a linear relation between the number of carbon atoms and the reduced ion mobility of the compounds within a certain homologous series, as a fast and intuitive method for K 0 estimation [74]. …”

Comprehensive software suite for the operation, maintenance, and evaluation of an ion mobility spectrometer

“…While this software package is designed to work with National Instrument hardware, the programmatic structure and hardware requirements outlined below may also serve as a framework for development in more open architectures. Recent work by Hariharan, et al shows promise towards identification of unknown IMS spectral peaks through linearization and database analysis [17]. This functionality should prove to be easily adaptable to the software system presented herein and provide stand-alone IMS instruments with capabilities previously reserved for tandem methods.…”