Methanol Residues Research Articles

Development and validation of a high-performance liquid chromatographic method for the determination of cyproterone acetate in human skin

In the framework of a preliminary study on the transdermal penetration of cyproterone acetate (CPA), a simple and rapid procedure involving an extraction step coupled to a HPLC-UV determination has been developed for the separation and quantification of CPA in the two main skin layers-epidermis and dermis-after local application. The separation of epidermis and dermis layers was carefully carried out by means of a sharp spatula after skin immersion in heated water at 65 °C. The two skin layers were then treated separately according to the same process: (1) sample homogenization by vibration after freezing with liquid nitrogen in a Mikro-Dismembrator ®; (2) CPA extraction with methanol after addition of the internal standard (betamethasone dipropionate); (3) centrifugation; (4) evaporation of a supernatant aliquot; (5) dissolution of the dry residue in methanol and addition of water; (6) centrifugation; (7) injection of a supernatant aliquot into the HPLC system. The separation was achieved on octadecylsilica stationary phase using a mobile phase consisting in a mixture of acetonitrile and water (40:60 (v/v)). The method was then validated using a new approach based on accuracy profiles over a CPA concentration range from 33 to 667 ng/ml for each skin layer. Finally, the method was successfully applied to the determination of CPA to several skin samples after topical application of different gel formulations containing CPA.

Performance of DMFC anodes with ultra-low Pt loading

The electrochemical behaviour of Pt-decorated unsupported Ru catalysts-based anodes has been investigated in direct methanol fuel cells (DMFCs). A preparation procedure allowing the surface decoration of unsupported Ru catalysts by Pt nanoparticles has been developed. DMFC power densities of 150 mW cm −2 at 130 °C have been achieved with ultra-low Pt loading anodes (0.1 mg cm −2) under air feed operation. Adsorbed methanolic residues stripping voltammetry analysis has been carried out to get information on the electrocatalytic activity of the Pt-decorated anodes in relation to the state-of-art carbon supported Pt–Ru (1:1) alloy and bare unsupported Ru catalysts.

Nonaqueous capillary electrophoretic separation of polyphenolic compounds in wine using coated capillaries at high pH in methanol.

Nonaqueous capillary electrophoretic separation of a group of flavonoids (quercetin, myricetin, catechin, epicatechin) and resveratrol in wine was investigated in methanol at high pH. Malonate background electrolyte (pH* 13.5, ionic strength I = 14.2 mmol/L) provided highly repeatable separations of the analytes. Tests of untreated and coated (poly(glycidylmethacrylate-co-N-vinylpyrrolidone)) capillaries showed the analysis to be faster (6.5 min vs. 25 min) and the repeatability better in the coated capillaries. The coating procedure was simple and highly repeatable and the coating was stable during 40-45 runs. Determination of the last migrating peaks (epicatechin, resveratrol and catechin) was achieved merely by evaporating the wine samples and reconstituting the residue in methanol. For determination of the first migrating peaks (quercetin and myricetin) the samples were submitted to solid-phase extraction in C8 cartridges.

Analysis of the high-temperature methanol oxidation behaviour at carbon-supported Pt–Ru catalysts

Methanol oxidation behaviour at three Pt–Ru catalysts varying by the concentration of active phase on the carbon support has been investigated in a wide temperature range (80–130 °C). An increase of the adsorbed methanolic residue stripping charge is observed with the increase of catalyst dispersion. As the temperature is increased, the stripping peak potential shifts more negatively accounting for a lower activation barrier for the reaction. An increase of temperature above 90 °C also produces a strong decrease in the coverage of adsorbed methanolic residues. The fuel cell performance is significantly enhanced by catalysts with intrinsically high catalytic activity, whereas the methanol reaction rate appears to be less influenced by an increase in coverage of active species. Catalysts characterized by a higher degree of alloying and metallic behaviour on the surface appear to be more active towards methanol oxidation. However, the physico-chemical properties of the catalysts have less influence on the anode electrochemical behaviour at high temperature since CO poisoning is alleviated under such conditions. The decrease of CO-like species coverage with temperature and the methanol tolerance characteristics of a Pt/C cathode are also discussed in relation to the crossover drawback of direct methanol fuel cells.

Kinetic study of methanol oxidation on carbon-supported PtRu electrocatalyst

Methanol electrooxidation was investigated on the carbon-supported PtRu electrocatalyst (1:1 atomic ratio) in acid media. X-ray diffraction measurement indicated alloying of Pt and Ru. Cyclic voltammetry of the sample reflects the amount of Ru in the catalyst and its ability to adsorb OH radicals. Tafel plots for the oxidation of 0.02–3 M methanol in the solutions containing 0.05–1 M HClO 4 and in the temperature range 27–40 °C showed reasonably well-defined linear region with the slope of about 115 mV dec −1 at the low currents, irrespective of the experimental conditions employed. Reaction order with respect to methanol was found to be 0.5. A correlation between methanol oxidation rate and pseudocapacitive current of OH adsorption on Ru sites was established. It was proposed that bifunctional mechanism is operative with the reaction between methanol residues adsorbed on Pt sites and OH radicals adsorbed on Ru sites as the rate-determining step.

Comparative efficacy and immunogenicity of Q fever chloroform:methanol residue (CMR) and phase I cellular (Q-Vax) vaccines in cynomolgus monkeys challenged by aerosol

Preliminary evidence gathered in rodents and livestock suggested that a phase I chloroform:methanol residue (CMR) extracted vaccine was safe and efficacious in protecting these animals from challenge with the obligate phagolysosomal pathogen ( Coxiella burnetii). Prior to the initiation of phase II studies in human volunteers, we compared, in non-human primates ( Macaca fascicularis), the efficacy of CMR vaccine with Q-Vax, a licensed cellular Australian Q fever vaccine that has been demonstrated to provide complete protection in human volunteers. Vaccine efficacy was assessed by evaluating thoracic radiographs and the presence of fever and bacteremia in monkeys challenged by aerosol with Coxiella burnetii. Changes in blood chemistries, hematology, behavior and pulmonary function were also examined. CMR, whether administered in single 30 or 100 μg doses or two 30 μg subcutaneous doses, gave equivalent protection in vaccine recipients as a single 30 μg dose of Q-Vax. In addition, vaccination resulted in significant, although temporary, increases in specific antibody titers against C. burnetii phases I and II antigens. The C. burnetii CMR vaccine may be an efficacious alternative to cellular Q fever vaccines in humans.

Electrooxidation of methanol on silver in alkaline medium

The electrooxidation of methanol on silver in alkaline medium has been studied by cyclic voltammetry and Fourier-transform infrared spectroscopy. It has been found that methanol electrooxidation starts together with the formation of multilayer Ag(II) oxide, which acts as a catalyst for the former process. The only oxidation product of methanol was formate, according to in situ FTIR spectroscopy results. In a negative potential sweep after a positive potential excursion in which methanol electrooxidation took place, a small anodic peak in the potential region of the beginning of the electroreduction of the Ag underpotential oxides showed that freshly reduced Ag has some activity for the electrooxidation of adsorbed methanol residues.

Investigation of unsupported Pt–Ru catalysts for high temperature methanol electro-oxidation

Two unsupported Pt–Ru catalysts, varying in the nature and content of RuOx species, were investigated for methanol electro-oxidation in a solid polymer electrolyte fuel cell at high temperature. The catalyst containing a lower amount of ruthenium oxide showed higher catalytic activity and lower mass transport limitations. A physicochemical investigation was carried out to support the interpretation of electrochemical results. Pt–Ru alloy appears more active than Pt–RuOx in the chemisorption of labile-bonded oxygenated species, which promote the oxidation of the methanolic residues adsorbed on the catalyst surface.

18-membered tetraimino macrocyclic complexes containing furan groups: stacking of two macrocycles and characterization of organic derivatives

The structures of the Na + and Pb 2+ complexes of a 18-membered macrocycle L 1 which are prepared by the reactions of 2,5-furandicarboxaldehyde and o-phenylenediamine in the presence of metal ions were studied by X-ray diffraction. The Na + complex has a methanol ligand and shows a stacking structure of the two complex cations in the crystal. The sandwich-type structure was found for the Pb 2+ complex. Two organic products obtained in the preparations of the macrocycles containing other metal ions were also characterized by X-ray analyses. One (L 1a) is a derivative of the macrocycle in which addition of two methanol residues were found. The other product (L 2) has a ring-contracted structure containing two benzimidazole residues. Structures of the macrocycles and sizes of the metal ions are discussed.

An X-ray photoelectron spectroscopic study on the effect of Ru and Sn additions to platinised carbons

Electro-catalytic oxidation of methanol is known to be promoted on Pt–Ru and Pt–Sn surfaces. Whilst Ru addition to Pt has been unambiguously acknowledged to enhance the methanol-oxidation reaction, the effect of Sn in the Pt–Sn alloy remains shrouded with inconsistencies. In order to further elucidate this problem, an X-ray photoelectron spectroscopic study is carried out on various carbon-supported Pt–Ru and Pt–Sn catalysts. It is argued that while Sn produces a modification in electronic environment around Pt-sites through a charge transfer in the Pt–Sn alloy, Ru-sites in the Pt–Ru system promote the formation of labile-bonded oxygenated species in the vicinity of methanolic residues adsorbed on Pt-sites facilitating them to oxidise as carbon-di-oxide.

Comparative efficacy of a Coxiella burnetii chloroform:methanol residue (CMR) vaccine and a licensed cellular vaccine (Q-Vax) in rodents challenged by aerosol

Q fever is an acute and self-limited febrile illness caused by the obligate intracellular bacterium Coxiella burnetii. While phase I cellular Q fever vaccines are efficacious in humans, vaccination of immune individuals may result in sterile abscesses and granulomas. The chloroform:methanol residue vaccine (CMR) was developed as a safer alternative. The efficacy of a licensed phase I cellular vaccine (Q-Vax) was compared with that of CMR vaccine in A/J mice and Hartley guinea pigs challenged with virulent phase I C. burnetii by aerosol. Both vaccines were efficacious. The CMR vaccine dose required to protect 50% of mice (PD 50) against lethal aerosol challenge (11 LD 50) was one-third of the Q-Vax dose. However, the PD 50 for CMR was four times the Q-Vax dose in guinea pigs challenged by aerosol (60 LD 50). It was concluded that CMR is an efficacious alternative to cellular Q fever vaccines for the prevention of Q fever. Published by Elsevier Science Ltd.

Potential oscillations during methanol oxidation at Pt-electrodes Part 1: experimental conditions

Potential oscillations during anodic methanol oxidation are studied by galvanostatic step experiments. Two types of galvanostatic step experiments are conducted by starting from an initial potential of approximately 450 and 20 mV respectively. Owing to the variation of the initial potential two potential regions are observed with oscillations of different shapes, frequencies and amplitudes. Oscillations, which occur at more negative potentials are generated by a small cathodic current before the galvanostatic step is performed. By applying a small cathodic current at the electrode the potential is kept below 50 mV, in a potential region where no methanol residues are formed. The type of oscillation, which occurs at higher potentials is independent of the initial experimental procedure. These results show that obviously different mechanisms are responsible for the observed oscillations.

Lamotrigine analysis in serum by high-performance liquid chromatography.

Lamotrigine is an anticonvulsant drug soon to be introduced to the North American market. It is chemically unrelated to any currently available antiepileptic drug. The objective of this study was to develop a quantitative high-performance liquid chromatography assay for lamotrigine in serum. Lamotrigine was extracted from serum at alkaline pH into ethyl acetate after addition of the internal standard (BW725C78). After mixing, the organic layer was evaporated to dryness before dissolving the residue in methanol for isocratic separation on a RP-8 column (5 microns) with a mobile phase of water/0.5 M phosphate buffer at pH 6.5/acetonitrile (790/10/200) with eluant monitoring at 306 nm. Calibration was performed with five serum standards (2-32 microM and recovery averaged 88% at 25 microM. Between-run precision was 4.1 and 2.5% C.V. at 13.6 and 31.6 microM, respectively. At room temperature, lamotrigine was stable for a minimum of 7 days. Interference studies were performed on serum specimens containing commonly monitored drugs. The only potentially interfering drug was carbamazepine, which elutes 2.5 times longer than lamotrigine. We conclude that this is a reliable method for quantitation of lamotrigine in serum.

Study of the electrocatalytic influence of Pt/Ru and Ru on the oxidation of residues of small organic molecules

Differential electrochemical mass spectrometry was employed for the investigation of the electrocatalytic activity of Ru deposits and of bimetallic Pt/Ru co-deposits. Using these modified electrodes the oxidation of the residues of CO, HCOOH and CH 3OH was studied by cyclic voltammetry. The corresponding mass intensity of CO 2 ( m/ z = 44) during the adsorbate oxidation clearly shows an increasing mass signal for CO 2 more than 200 mV more negative at Pt/Ru in comparison with that on pure Pt. In addition, the formation of methanol residues on the Pt/Ru surfaces was studied and compared with those on pure Pt and pure Ru. It is shown that the peak potentials for the formation of CH 3OH residues at Pt/Ru surfaces are shifted by 70 mV in the negative direction compared with pure Pt, while pure Ru shows no formation of methanol residues. Nevertheless, on the Ru surfaces CO and HCOOH do form adsorbates. The results presented demonstrate that the bifunctional mechanism, proposed earlier for the methanol oxidation at Pt/Ru, must be modified.

The production of labeled betaine by incubation of osmolyte-freePseudomonas aeruginosa with radioactive choline

A simple, efficient, and economical method is presented for the preparation of radioactive betaine. It involves the incubation of radioactive choline with osmolyte-freePseudomonas aeruginosa previously grown in hyperosmolar medium with choline as an osmoprotectant. The summarized procedure was as follows: (i) bacteria were grown in high Pi basal salt medium (HPi-BSM) with 20mm succinate, 18.7mm NH4Cl, 0.8m NaCl, and 1mm nonradioactive choline. After the bacterial pellet was obtained, it was suspended in deionized water to release osmolytes accumulated during growth; (ii) suspension of the pellet, free of osmolytes, in hyperosmolar HPi-BSM with [methyl-14C]-choline (55 nCi/nmol) without the carbon and nitrogen sources. Incubation of the mixture at 37°C for 8–30 h. When only 10% of the initial radioactivity remained in the supernatant, it was withdrawn after centrifugation and the pellet suspended in deionized water. This step released the accumulated betaine plus some contaminants. Purification of betaine contained in the aqueous supernatant was carried out after rotoevaporation to dryness and solubilization of the residue in methanol. The methanolic extract was rotoevaporated to dryness, the residue solubilized in 10% acetic acid and transferred to a Dowex 50-X8 column. After the column was washed with water and 2m NH4OH, betaine was eluted by the addition of 4m NH4OH. The total procedure for obtaining pure radioactive betaine resulted in a yield of 80%. The product obtained was chemically and radiochemically pure, with a specific radioactivity of 54±1 nCi/nmol.

Methanol oxidation on carbon-supported platinum-tin electrodes in sulfuric acid

A study is made of the electrooxidation of methanol in sulfuric acid on carbon-supported electrodes containing platinum-tin bimetal catalysts that are prepared by an in situ potentiometric-characterization route. The catalysts are investigated by employing chemical analyses, X-ray diffraction (XRD), X-ray absorption-near-edge spectroscopy (XANES) and X-ray photoelectron spectroscopy (XPS) data in conjunction with electrochemical measurements. From the electrochemical data, it is inferred that while an electrode with (3:1) Pt-Sn/C catalyst involves a two-electron rate-limiting step akin to platinum-on-carbon electrodes, it is shifted to a one-electron mechanism on electrodes with (3:2)Pt-Sn/C, (3:3)Pt-Sn/C, and (3:4)Pt-Sn/C catalysts. The study suggests that the tin content in the platinum-tin bimetal catalyst produces: (i) a charge transfer from tin to platinum; (ii) an increase in the coverage of adsorbed methanolic residues with increase in the tin content, as indicated by the shift in rest potential of the electrodes towards the reversible value for oxidation of methanol (0.043 V versus SHE), and (iii) a decrease in the overall content of higher valent platinum sites in the catalyst.

Immunisation de chiens avec des vaccins contre la fièvre Q: comparaison entre des vaccins de <em>Coxiella burnetii</em> de phase I, phase II et du RCM de phase I

Q fever vaccines were tested in mixed breed dogs by vaccinating them with formalin-killed Coxiella burnetii whole cells (WC) in either phase I (WCI) or phase II (WCII), or the chloroform: methanol residue (CMR) subunit of phase I cells. Phase I vaccines mixed (1:1) with Freund's incomplete adjuvant (FIA) induced humoral immune responses to phases I and II antigens as measured by microagglutination assay. The CMR vaccine mixed (1:1) with FIA induced greater antigen-specific antibody levels to both phases I and II antigens than the corresponding WCI vaccine. The WCII vaccine induced antibody responses to only phase II antigens. The time course of erythema and induration after skin testing with C. burnetii antigens were suggestive of cell-mediated immunity (CMI). Although granulomas were observed with only WCI and WCII, none of the skin test antigens induced abscesses at the injection site. In contrast, axillary nodes draining the vaccine injection site developed sterile draining abscesses in all dogs by days 19 to 24 for the WCI and CMR, and day 104 for the WCII vaccines. The abscesses had resolved within 30 days after first appearance. Responses to Con A and PHA and recall antigens of lymphocytes from the blood, axillary and mesenteric nodes, and spleen at 222 days after vaccination were variable among dogs. Lymphocytes from various organs responded to one or more of the recall antigens and to both mitogens in the absence or presence of indomethacin. Although these Q fever vaccines induced humoral and CMI, either the antigens or FIA caused sterile draining abscesses.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of ruthenium adatoms on the oxidation of chemisorbed species of methanol on a platinum electrode by a radiochemical method

Methanol electrosorption and residue electro-oxidation on platinized platinum electrodes have been investigated by cyclic voltammetry as well as by a radiochemical method. Using both methods simultaneously allows the mechanism of methanol residue oxidation to be elucidated. The oxidized ruthenium adatoms are oxidants in the above process.

Vaccines against coxiellosis and Q fever. Development of a chloroform:methanol residue subunit of phase I Coxiella burnetti for the immunization of animals.

We have demonstrated the safety, immunogenicity, and efficacy of the WC and CMR vaccines in guinea pigs. Vaccination of guinea pigs with either WC or CMR protects animals against challenge with virulent C. burnetii. A total of 2 micrograms of either WC or CMR vaccine was a significant priming dose. A total of 20 micrograms gave complete protection against lethal challenge. Detection of antibodies to phase II cells by microaglutination, after vaccination with either WC or CMR and before lethal challenge, correlated with the ability of guinea pigs to mount a protective immune response. The PD50 values for WC and CMR vaccines, administered as a single dose, were 0.3 and 1.4 micrograms per animal, respectively. In contrast, the PD50 values for the WC and CMR vaccines, administered as two doses, were 0.83 and 0.72 micrograms per animal, respectively. Although the PD50 values for the two vaccines are similar, the CMR vaccine is preferred over the WC vaccine because it induces significantly fewer adverse reactions, and repeat injections can be given. Unvaccinated guinea pigs do not clear infectious microorganisms after challenge infection. Vaccination before challenge infection reduces the infectious load of C. burnetti in the blood and in various organs of the animals. When vaccinated animals were challenge infected and treated with rifampicin, the microorganisms were not eliminated from various organs. However, the combination of vaccination, challenge, and rifampicin treatment is effective in reducing the number of infectious microorganisms in some of these sites. We have demonstrated the safety and immunogenicity of the CMR vaccine in sheep and goats. Animals that were seropositive for one or more antigens developed significant levels of antibodies to alternate antigens, but no adverse reactions were observed at the site of s.c. injection of the CMR vaccine. This demonstrates that seropositive animals can be successfully immunized with this vaccine. These results also indicate that a long-term vaccination program using the CMR vaccine has the potential for producing animals with significant antibody titers to C. burnetii and perhaps lifelong immunity. The goal of a Q fever vaccination program is to produce immunized animals that are able to clear completely the infectious microorganisms. The appropriate vaccination schedule to render adult animals and their offspring "Q fever-free" should now be thoroughly investigated.

Simultaneous determination of molybdenum, vanadium, gallium, copper, iron and indium as 8-quinolinolate complexes by high-performance liquid chromatography

8-Quinolinol (HQ) was used as a precolumn chelating reagent for the reversed-phase high-performance liquid chromatographic (HPLC) determination of Mo(VI), V(V), Ga(III), Cu(II), FE(III) and ln(III). The metal—HQ complexes were separated on a C 18 column using a mobile phase of methanol-water (67:33, v/v) containing 1.25 · 10 −3 M HQ and 0.02 M chloroacetate (pH 3.5). The metal-HQ complexes were preconcentrated by solvent extraction, evaporation of the solvent and dissolution of the residue in methanol. After preconcentration, μg 1 −1 levels of the metals can be determined by HPLC with satisfactory precision. The proposed method was applied to the simultaneous determination of Mo(VI), V(V), CU(II) and FE(III) in sea water.