PubMed · 15416746
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A L G REES, J A SPINK. 1950-04-22. Line-breadth in electron diffraction.. https://doi.org/10.1038/165645a0
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Linearity and detection thresholds of atmospheric pressure ionization-mass spectrometry (API-MS) were determined for 11 aroma compounds in air at concentrations ranging from 50 ppb to approximately 450 ppm (moles of volatile per mole of air). In most cases, the protonated molecular ion (i.e., m/z = M + 1) was the base peak throughout the range; however, some compounds showed an increase in fragmentation at lower concentrations. Detection limits varied greatly (from 50 ppb to 14 ppm) depending upon the aroma compound being measured. The linear range was also strongly dependent upon the aroma compound, with values ranging from <10-fold change in concentration to >4000-fold change in concentration depending upon the volatile being studied. The two volatiles with poor detection thresholds also exhibited the smallest linear range. Most compounds had linear ranges of >200. There was no apparent relationship between gas-phase basicity and either detection limit or linear range.
Attempts were to develop microemulsion systems using medium chain triglyceride, deionized water, and TPGS as surfactant for the oral delivery of protein drugs or poorly water-soluble drugs. Phase diagrams were constructed to elucidate the phase behavior of systems composed of Captex 300 and water with D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS) as main surfactant, polysorbates (Tween 20, Tween 40, Tween 60 and Tween 80) as adjuvant surfactants, and polyethylene glycols (PEG 400 and PEG 600) and polyols (ethanediol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol and glycerin) as cosurfactants. The ratios of TPGS to Tweens, PEGs or polyols (K(m)) were set at 4/1, 2/1, 1/1, 1/2, and 1/4. The phase diagram for H(2)O/Captex 300/TPGS system reveals that when TPGS was used as a sole surfactant, it is not capable of producing isotropic solutions of water and oil over a wide range of the compositions. H(2)O/Captex 300/TPGS/Tweens systems with various K(m), regardless of the adjuvant surfactant used were capable of producing an isotropic phase. The extension of microemulsion phase and the presence and extension of the gel phase were found to be dependent on the surfactant mixture. The phase diagrams of H(2)O/Captex 300/TPGS systems using polyols as cosurfactants demonstrate that the types of polyols have a slight effect on the region of existence of the microemulsions. Comparison between the isotropic regions for the polyols system reveals that as the relative concentration of polyols increase, the isotropic region decrease in size. This decrease is towards the S(mix)-water axis indicating that as the relative concentration of polyols increases the maximum amount of oil solubilized decreases. The gel region decreased in size with the increase of polyols weight ratio. All polyols do not solubilized Captex 300 without using TPGS as surfactant.
The radical scavenging potential of phenolic compounds occurring in Olea europaea and of recently identified hydroxytyrosol metabolites was evaluated by means of quantum chemical calculations. The bond dissociation enthalpy (BDE) of phenolic hydroxyl groups and the ionization potential (IP) were calculated as descriptors to predict the H-atom-donating and electron-donating abilities of antioxidants, respectively. Catechol derivatives had the lowest BDE values (77.7-80.1 kcal/mol) whereas the lignans, pinoresinol and 1-acetoxypinoresinol, and other monophenols had much higher BDE values (85.1-88.0 kcal/mol), which suggested a lower potential for radical scavenging. Side chain characteristics were not found to affect the size of BDE values although differences in lipophilicity (on the basis of calculated Log P values) indicate variability in the activity in real systems. Conclusions for the antioxidant potential could not be drawn based on the IP values. Lack of experimental data for most of the studied compounds due to oxidative instability and difficulties in synthesis or isolation supports the usefulness of a computational approach for those interested in the antioxidant potential of phenolics encountered in O. europaea products.