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Ion Mobility Studies on the Negative Ion-Molecule Chemistry of Isoflurane and Enflurane.

ABSTRACT: In the present work we present an investigation of the negative ion-molecule chemistry of the anaesthetics isoflurane, ISOF, and enflurane, ENF, in an ion mobility spectrometry/mass spectrometry (IMS/MS), in both air and nitrogen. Hexachloroethane (HCE) was introduced in both air and nitrogen to produce Cl^- as a reactant ion. This study was undertaken owing to uncertainties in the chemical processes, which lead to the cluster ions reported in other work (Eiceman et al. Anal. Chem. 61, 1093-1099, 1). In particular for ISOF the product ion observed was ISOF.Cl^-, and it was suggested that the Cl^- was formed by dissociative electron attachment (DEA) although there was mention of a chlorine containing contaminant. We show in this study that ISOF and ENF do not produce Cl^- in an IMS system either by capture of free electrons or reaction with O₂^-. This demonstrates that the Cl^- containing ions, reported in the earlier study, must have been the result of a chlorine containing contaminant as suggested. The failure of ISOF and ENF to undergo DEA was initially surprising given the high calculated electron affinities, but further calculations showed that this was a result of the large positive vertical attachment energies (VAEs). This experimental work has been supported by electronic structure calculations at the B3LYP level, and is consistent with those obtained in a crossed electron-molecular beam two sector field mass spectrometer. An unusual observation is that the monomer complexes of ISOF and ENF with O₂^- are relatively unstable compared with the dimer complexes. Graphical Abstract ᅟ.

SUBMITTER: Gonzalez-Mendez R

PROVIDER: S-EPMC5393067 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

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Ion Mobility Studies on the Negative Ion-Molecule Chemistry of Isoflurane and Enflurane.

González-Méndez Ramón R Watts Peter P Howse David C DC Procino Immacolata I McIntyre Henry H Mayhew Chris A CA

Journal of the American Society for Mass Spectrometry 20170221 5

In the present work we present an investigation of the negative ion-molecule chemistry of the anaesthetics isoflurane, ISOF, and enflurane, ENF, in an ion mobility spectrometry/mass spectrometry (IMS/MS), in both air and nitrogen. Hexachloroethane (HCE) was introduced in both air and nitrogen to produce Cl<sup>-</sup> as a reactant ion. This study was undertaken owing to uncertainties in the chemical processes, which lead to the cluster ions reported in other work (Eiceman et al. Anal. Chem. 61, ...[more]

PMID: 28224395

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Project description:The structural modifications of the dipalmitoylphosphatidylcholine (DPPC) organization induced by increasing concentration of the volatile anesthetic enflurane have been studied by differential scanning calorimetry, small-angle, and wide-angle x-ray scattering. The interaction of enflurane with DPPC depends on at least two factors: the enflurane-to-lipid concentration ratio and the initial organization of the lipids. At 25 degrees C (gel state), the penetration of enflurane within the lipids induces the apparition of two different mixed lipid phases. At low anesthetic-to-lipid molar ratio, the smectic distance increases whereas the direction of the chain tilt changes from a tilt toward next-neighbors to a tilt between next-neighbors creating a new gel phase called L(beta')(2NNN). At high ratio, the smectic distance is much smaller than for the pure L(beta') DPPC phase, i.e., 50 A compared to 65 A, the aliphatic chains are perpendicular to the membrane and the fusion temperature of the phase is 33 degrees C. The electron profile of this phase that has been called L(beta)(i), indicates that the lipids are fully interdigitated. At 45 degrees C (fluid state), a new melted phase, called L(alpha)(2), was found, in which the smectic distance decreased compared to the initial pure L(alpha)(1) DPPC phase. The thermotropic behavior of the mixed phases has also been characterized by simultaneous x-ray scattering and differential scanning calorimetry measurements using the Microcalix calorimeter of our own. Finally, titration curves of enflurane effect in the mixed lipidic phase has been obtained by using the fluorescent lipid probe Laurdan. Measurements as a function of temperature or at constant temperature, i.e., 25 degrees C and 45 degrees C give, for the maximal effect, an enflurane-to-lipid ratio (M/M), within the membrane, of 1 and 2 for the L(alpha)(2) and the L(beta)(i) lamellar phase respectively. All the results taken together allowed to draw a pseudo-binary phase diagram of enflurane-dipalmitoylphosphatidylcholine in excess water.

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Ion Mobility Studies on the Negative Ion-Molecule Chemistry of Isoflurane and Enflurane.

Publications

Ion Mobility Studies on the Negative Ion-Molecule Chemistry of Isoflurane and Enflurane.

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