PubMed · 13744576
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D RUFFILLI. [Hydrostatic pressure as pathogenic cause].. https://pubmed.ncbi.nlm.nih.gov/13744576/
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The reaction products of alpha- or gamma-tocopherol with nitric oxide in the presence of molecular oxygen were isolated and characterized. The consumption of tocopherols and the formation of the major products were monitored by high-performance liquid chromatography (HPLC) by a gradient elution method. The quantitative analysis of these compounds with UV-Vis detectors, however, was interfered by several minor products having similar UV spectra and retention times as those of the major ones. In order to establish a quantitative analytical method for the products, we investigated other detection methods, and found that atmospheric pressure chemical ionization (APCI), LC-MS was a more selective and better analytical method for these compounds.
The atmospheric pressure (AP) matrix-assisted laser desorption/ionization (MALDI) technique described to date has proven to be a convenient and rapid method for soft ionization of biomolecules. However, this technique, like other AP ionization methods, has so far suffered from a low efficiency in transmitting ions from atmospheric pressure into the vacuum of the mass spectrometer (MS). In this work, a novel technique we termed pulsed dynamic focusing, or PDF, which improves the ion transmission efficiency and sensitivity of AP-MALDI by over an order of magnitude, is described. Pulsed dynamic focusing operates on the basis of pulsing a high-voltage extraction field to zero, when ions are just outside of the MS entrance, to allow the intake gas flow of the MS to effectively entrain the ions into the MS. Results from application of the PDF technique to an AP-MALDI ion trap MS demonstrated that in comparison to static AP-MALDI operation (1). up to 2.1 times more ions from a given laser shot could be transferred into the MS, (2). applying higher voltages in combination with the switching scheme yielded up to 1.6-times-higher ion intensities, and (3). a 3-times-larger laser spot area could be utilized. The combination of these factors produced an enhancement in throughput and sensitivity, as measured by the ions detected per unit time, of over 12 times for a digest sample of bovine serum albumin. In addition, the PDF technique proved to make AP-MALDI less sensitive to laser positioning, creating a more robust ion source in comparison to static AP-MALDI.
Interest in thin films of functional organic materials has increased enormously in recent years because of the wide range of possible applications. Here we report an experimental setup for processing various organic materials into thin structured films under atmospheric pressure. The technique is based on an electrospray process. Microdroplets are initially formed and dried, generating ions that are extracted by electrostatic lenses. Thin structured films are then produced by the deposition of the resulting ion beam onto a moveable target. The technique offers several interesting features, including precise control of film thicknesses. We have also made experiments to investigate structured deposition, this being the first step towards the production of thin films where in all three dimensions the chemical composition can be chosen at will. This might provide a simple approach towards creating thin structured films and composites that are currently unattainable.