Surface characterization of plasma sprayed oxide materials: estimation of surface acidity using mass titration

The aim of this study was to characterize the influence of plasma spraying on the point of zero charge (PZC) of Al2O3-, Cr2O3- and TiO2-based materials. PZC is one of the most important parameter, which describes the acidity of oxide material in aqueous environments. PZC values of several plasma sprayed oxides were determined using mass titration method. Studies were performed for initial spray powders and plasma sprayed coating materials. In addition, mass titration experiments were performed for water-washed and nonwashed samples. It was found that mass titration is a suitable method to estimate the surface acidity of relatively coarse sample powders. It was found for most of the studied materials that the limiting pH values (assumed to be close PZC) were close to those reported in literature for the PZC values of traditionally manufactured oxide materials. On the other hand, mass titration curves of some oxide samples showed unexpected deviation in curve shapes and limiting pH. These deviations were probably due to selective dissolution of sample contaminations or sample material.     

On the Mechanism of the Reactivity of 1,3‐Dialkylimidazolium Salts under Basic to Acidic Conditions: A Combined Kinetic and Computational Study

Comprehensive spectroscopic kinetic studies illustrate an alternative mechanism for the traditional free‐carbene intermediated H/D exchange reaction of 1,3‐dialkylimidazolium salts under neutral (D₂O) and acidic conditions (DCl/D₂O 35 wt % solution). The deuteration of high purity [bmim]Cl in D₂O is studied at different temperatures, in absence of catalyst or impurities, to yield an activation energy. DFT transition‐state modelling, of a small water cluster and [bmim] cation, also yields an activation energy which strongly supports the proposed mechanism. The presence of basic impurities are shown to significantly enhance the exchange reaction, which brings into question the need for further analysis of technical purities of ionic liquids and the implications for a wide range of chemical reactions in such media.     

An homologous series of benzodiazepine retention index standards for gas chromatography

An homologous series of benzodiazepine retention index standards (the R-series) has been synthesized and the gas chromatographic behavior of the series investigated on NB-54 and NB-1701 capillary columns. The compounds were stable, exhibited symmetrical peak shapes, and fairly linear retention behavior was observed on both columns. The series can be coinjected with every sample to enable the high precision analysis of toxicological samples; screening for 20 benzodiazepine drugs was possible in 23 minutes (including cooling). The R-series method was compared with a retention index method based on a series of benzodiazepine drugs as standards and with a method employing relative retention times. The precision of the R-series method was found to be generally better than that of the two other methods in both long- and short-term studies.     

Detection of volatile organic sulfur compounds in water by headspace gas chromatography and membrane inlet mass spectrometry

Two gas chromatographic methods, GC-FID (flame ionization detection) and GC-ELCD (electrolytic conductivity detector) are compared in tlie analysis of volatile organic sulfur compounds (VOSCs) in water samples with a membrane inlet mass spectrometry (MIMS) technique. Carbon disulfide, ethanethiol, dimethyl sulfide, ethyl-methyl sulfide, thiophene, and dimethyl disulfide were used as test compounds. Linear dynamic ranges were found to be two decades with the GC-ELCD method and four decades with the GC-FID and MIMS methods. Detection limits were at low (μg/1 levels with the two gas chromatographic methods and clearly below μg/1 level with the MIMS method. Analysis of one sample takes 40 min with the gas chromatographic methods and five minutes with the MIMS method. The selectivity was good, especially with the GC-ELCD and the MIMS method. In addition, quantitative results obtained with spiked water samples by the three methods are compared.     

Poly(dimethylsiloxane) electrospray devices fabricated with diamond-like carbon-poly(dimethylsiloxane) coated SU-8 masters

This study presents coupling of a poly(dimethylsiloxane) (PDMS) micro-chip with electrospray ionization-mass spectrometry (ESI-MS). Stable electrospray is generated directly from a PDMS micro-channel without pressure assistance. Hydrophobic PDMS aids the formation of a small Taylor cone in the ESI process and facilitates straightforward and low-cost batch production of the ESI-MS chips. PDMS chips were replicated with masters fabricated from SU-8 negative photoresist. A novel coating, an amorphous diamond-like carbon-poly(dimethylsiloxane) hybrid, deposited on the masters by the filtered pulsed plasma arc discharge technique, improved significantly the lifetime of the masters in PDMS replications. PDMS chip fabrication conditions were observed to affect the amount of background peaks in the MS spectra. With an optimized fabrication process (PDMS curing agent/silicone elastomer base ratio of 1/8 (w/w), curing at 70 degree C for 48 h) low background spectra were recorded for the analytes. The performance of PDMS devices was examined in the ESI-MS analysis of some pharmaceutical compounds and amino acids.     

Identification of ozone-oxidation products of oxycodone by electrospray ion trap mass spectrometry

The products of oxycodone oxidized by ozone were characterized by electrospray ionization-tandem mass spectrometry (ESI--MS/MS). Liquid Chromatography(LC)--MS analyses revealed that the main constituents in the oxidation reaction mixture included the protonated molecules m/z 316, corresponding to oxycodone, and m/z 332, m/z 348, m/z 366, corresponding to the oxidation products. ESI--MS/MS and MS(n) spectra were used to study oxycodone fragmentation in detail and to characterize the structures of oxidation products. The results show that the oxidation products were formed by addition of one or two oxygen atoms or by addition of three oxygen and two hydrogen atoms to oxycodone. The fragmentation of the oxidation products also shows that the aromatic ring oxidizes due to rupture of the C-3--C-4 bond during product formation.     

Influence of Additives on Capillary Absorption of Aqueous Solutions into Asymmetric Porous Ceramic Substrate

The effect of divalent and trivalent salts (CaCl(2), CaBr(2), MgCl(2), MgBr(2), LaCl(3), CeCl(3), La(NO(3))(3), and Ce(NO(3))(3)) on the micelle formation in C(8)-lecithin solutions was investigated using the techniques of static and dynamic light scattering. The critical micelle concentration (cmc), mean hydrodynamic radius (R(h)), gyration radius (R(g)), and weight-average molecular weight of the micelles were measured as functions of salt identity and concentration, amphiphile concentration, and temperature. It was found that the micelles in solutions of magnesium are less likely to form and less stable; their standard enthalpy is less exothermic as the ionic strength increases. On the contrary, the micelles in solutions of calcium and trivalent salts form easily, and are more stable; their standard enthalpy is also more exothermic as the ionic strength increases. Based on our model of the Gibb's free energy for the salt-added solutions, we obtained the following formula for the effect of salts on cmc: ln(cmc)'=ln(cmc)+k(1) I(1/2)+k(2)I, where (cmc)' and (cmc) are the critical micelle concentrations in salt-added and salt-free solutions, respectively, I is the ionic strength, and k(1) and k(2) are the salt effect parameters. The agreement between the formula and the experimental data for all the systems under study shows that the formula is more satisfactory than those suggested previously by other authors in describing the effect of salts on the cmc in the micellar solutions of not only zwitterionic but also nonionic surfactants. Copyright 2001 Academic Press.     

Optimal Maps and Exponentiation on Finite-Dimensional Spaces with Ricci Curvature Bounded from Below

We prove existence and uniqueness of optimal maps on \(\mathsf{RCD}^*(K,N)\) spaces under the assumption that the starting measure is absolutely continuous. We also discuss how this result naturally leads to the notion of exponentiation and to the local-to-global property of \(\mathsf{RCD}^*(K,N)\) bounds.     

Direct analysis of illicit drugs by desorption atmospheric pressure photoionization

The feasibility of desorption atmospheric pressure photoionization (DAPPI) in the direct analysis of illicit drugs was demonstrated by the analysis of confiscated drug samples of various forms such as tablets, blotter paper, and plant resin and bloom. 3,4-Methylenedioxymethamphetamine (MDMA), amphetamine, phenazepam, and buprenorphine were detected from the analyzed tablets, lysergic acid diethylamide (LSD) and bromobenzodifuranylisopropylamine (bromo-Dragonfly, ABDF) from blotter paper, and Delta(9)-tetrahydrocannabinol (THC) and cannabinol from Cannabis Sativa bloom and resin. The amphetamines, phenazepam and ABDF showed protonated molecules independent of the solvent used, whereas buprenorphine, LSD and the cannabinoids showed molecular ions with toluene and protonated molecules with acetone as the solvent.     

Quantitative retinal-blood flow measurement with three-dimensional vessel geometry determination using ultrahigh-resolution Doppler optical coherence angiography

Retinal blood flow quantification by retinal vessel segmentation with Doppler optical coherence angiography is presented. Vessel diameter, orientation, and position are determined in an en face vessel image and two representative cross-sectional flow images of the vessel. Absolute blood flow velocity is calculated with the help of the measured Doppler frequency shift and determined vessel angle. The volumetric flow rate is obtained with the position and the region of the vessel lumen. The volumetric blood flow rate of retinal arteries before and after a bifurcation is verified in a healthy human eye.