For the first time, a traditional radioactive nickel (63Ni) beta emission ionization source for ion mobility spectrometry was employed with an atmospheric pressure ion mobility orthogonal reflector time-of-flight mass spectrometer (IM(tof)MS) to detect a chemical warfare agent (CWA) simulant from aerosol samples. Aerosol-phase sampling employed a quartz cyclonic chamber for sample introduction. The simulant reference material, which closely mimicked the characteristic chemical structure of CWAs as defined and described by Schedule 1, 2, or 3 of the Chemical Warfare Convention treaty verification, was used in this study. An overall elevation in arbitrary signal intensity of approximately 1.0 orders of magnitude was obtained by the progressive increase of the thermal AP-IMS temperature from 75 to 275 degrees C. A mixture of one G-type nerve simulant (dimethyl methylphosphonate (DMMP)) in four (water, kerosene, gasoline, diesel) matrixes was found in each case (AP-IMS temperature 75-275 degrees C) to be clearly resolved in less than 2.20 x 10(4) micros using the IM(tof)MS instrument. Corresponding ions, masses, drift times, K(o) values, and arbitrary signal intensities for each of the sample matrixes are reported for the CWA simulant DMMP.
Summary Accurate prediction of neurological outcome in survivors of cardiac arrest may be difficult. We report the case of a 44‐year‐old survivor of a hypoxic cardiac arrest who repeatedly developed relentless myoclonic jerks on attempted discontinuation of his propofol infusion. These were initially thought to represent myoclonic status epilepticus before the correct diagnosis of Lance–Adams syndrome was made. Lance–Adams syndrome is a rare disorder seen in survivors of profound hypoxic episodes. It is characterised by intention myoclonus but preserved intellect. Accurate distinction between myoclonic status epilepticus and Lance–Adams syndrome is vital as they have very different prognoses. The different pathophysiology and distinguishing clinical features of these two conditions are highlighted.
The temperature dependence of the stability of the adlayer formed at the interface between Au(111) and a coronene-heptanoic acid solution is reported. At coronene concentrations above 1.5 × 10-4 M and at 21 °C, a dense coronene adlayer is observed. At higher temperatures (up to about 60 °C) or in a more dilute solution, a coadsorbed coronene-heptanoic acid structure is observed. This coadsorbed structure is very hardy, surviving exposure to the pure solvent for periods of many minutes and temperatures as high as 105 °C. Loss of the ordered monolayer with high temperature solvent exposure is also accompanied by the formation of at least two additional surface structures involving both coronene and heptanoic acid. This work demonstrates that there is much to be learned by exploring the solution-solid interface at elevated temperatures with STM.
The use of an atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI) source was employed with an atmospheric pressure ion mobility spectrometer (APIMS) and an orthogonal acceleration reflector time-of-flight mass spectrometer (TOFMS) to analyze dipeptide and biogenic amine mixtures from a liquid glycerol 2,5-dihydroxybenzoic acid (DHB) matrix. Improved sensitivities were obtained by the addition of a localized electrical (corona) discharge in conjunction with the AP-MALDI source. Enhanced sample ionization efficiency created by this combination provided an overall elevation in signal intensity of approximately 1.3 orders in magnitude. Combinations of three dipeptides (Gly-Lys, Ala-Lys, and Val-Lys) and nine biogenic amines (dopamine, serotonin, B-phenylethylamine, tyramine, octopamine, histamine, tryptamine, spermidine, and spermine) were resolved in less than 18 ms. In many cases, reduced mobility constants (K(o)) were determined for these analytes for the first time. Ion mobility drift times, flight times, arbitrary signal intensities, and collision-induced dissociation (CID) fragmentation product signatures are reported for each of the samples.
The ion mobilities and their respective masses of several classes of amines (primary, secondary, and tertiary) were measured by electrospray ionization atmospheric pressure ion mobility time-of-flight mass spectrometry IM(tof)MS. The experimental data obtained were comparatively analyzed by the one-temperature kinetic theory of Chapman-Enskog. Several theoretical models were used to estimate the collision cross-sections; they include the rigid-sphere, polarization-limit, 12-6-4, and 12-4 potential models. These models were investigated to represent the interaction potentials contained within the collision integral that occurs between the polyatomic ions and the neutral drift gas molecules. The effectiveness of these collision cross-section models on predicting the mobility of these amine ions was explored. Moreover, the effects of drift gas selectivity on the reduced-mass term and in the collision cross-section term was examined. Use of a series of drift gases, namely, helium, neon, argon, nitrogen, and carbon dioxide, made it possible to distinguish between mass effects and polarizability effects. It was found that the modified 12-4 potential that compensates for the center of charge not being at the same location as the centers of mass showed improved agreement over the other collision cross-section models with respect to experimental data.
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