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Perchloric Acid (perchloric + acid)
Terms modified by Perchloric Acid Selected AbstractsChemInform Abstract: Silica Supported Perchloric Acid (HClO4,SiO2): An Efficient and Recyclable Heterogeneous Catalyst for the One-Pot Synthesis of Amidoalkyl Naphthols.CHEMINFORM, Issue 35 2008Hamid Reza Shaterian Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] One-Step Synthesis of Lumazine and Xanthine: First Co-Crystal of Lumazine and Perchloric Acid with a Unique Monohydrated Hydronium Ion (H5O2+) Mediated Supramolecular Assembly of the Lumazine Dimer.CHEMINFORM, Issue 50 2007Shyamaprosad Goswami Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Perchloric Acid Adsorbed on Silica Gel (HClO4,SiO2) as an Inexpensive, Extremely Efficient, and Reusable Dual Catalyst System for Acetal/Ketal Formation and Their Deprotection to Aldehydes/Ketones.CHEMINFORM, Issue 20 2007Raj Kumar Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Perchloric Acid Impregnated on Silica Gel (HClO4/SiO2): A Versatile Catalyst for Michael Addition of Thiols to the Electron-Deficient Alkenes.CHEMINFORM, Issue 33 2006Abu T. Khan Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Novel corrective equations for complete estimation of human tissue lipids after their partial destruction by perchloric acid pre-treatment: high-resolution 1H-NMR-based studyNMR IN BIOMEDICINE, Issue 2 2008Niraj Kumar Srivastava Abstract Owing to the small quantity of tissue available in human biopsy specimens, aqueous and lipid components often have to be determined in the same tissue sample. Perchloric acid (PCA) used for the extraction of aqueous metabolites has a deleterious effect on lipid components; the severity of the damage is not known. In this study, human muscle tissue was first treated with PCA to extract aqueous metabolites, and the residue was then used for lipid extraction by conventional methods, i.e. the methods of Folch and Bligh & Dyer and a standardised one using methanol/chloroform (1:3, v/v) used in our laboratory. A 1H-NMR spectrum was obtained for each lipid extract. Lipid was quantified by measuring the integral area of N+ -(CH3)3 signals of phospholipids (PLs). Triacylglycerol (TG) and cholesterol (CHOL) were quantified using the -CH2 - signals of glycerol and the C18 methyl signal, respectively. This study shows that prior use of PCA caused marked attenuation of TG, PL, and CHOL. This was confirmed by recovery experiments and observation of the direct effect of PCA on the standard lipid components. On the basis of the quantity of lipid lost in each case, three novel equations (with respect to TG, PL, and CHOL) were derived. Application of these equations to lipid quantities estimated in different pathological tissues after PCA pre-treatment produced values equivalent to those estimated without PCA use. This study conclusively shows that PCA pre-treatment damages all three lipid moieties, TG, PL, and CHOL. When PCA is used in a fixed ratio to the tissue, the lipid damage is also proportional and correctable by statistically derived equations. These equations will be useful in human biopsy specimens where aqueous and lipid components have to be studied using the same tissue sample because of the small quantity available. Copyright © 2007 John Wiley & Sons, Ltd. [source] Novel (3,4)- and (4,5)-Connected Lanthanide Metal,Organic FrameworksEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2008Xian-Wen Wang Abstract The three-dimensional lanthanide noninterpenetrating metal,organic frameworks formulated as [Ln(3,5-pdc)(C2O4)0.5(H2O)2]·H2O (Ln = LuIII, GdIII, TmIII and YbIII for complex 1,4, respectively; 3,5-pdc = 3,5-pyridinedicarboxylate) were synthesized by hydrothermal reactions of 3,5-H2pdc with lanthanide oxide and perchloric acid. Compound 1 shows (3,4)-connected (4.82)(4.85) dmc-type topological network, and complexes 2,4 display the novel (4,5)-connected (44.6.8)(44.62.84) xww-type topology. The lanthanide-mediated transformation of CO2 to oxalate under hydrothermal conditions was observed. The fluorescence properties of complexes 1,4 were investigated. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Synthesis of Both Enantiomers of Conduritol C Tetraacetate and of meso -Conduritol D Tetraacetate by Oxidation of Benzoquinone Bis(ethylene acetal)EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 5 2007Martin Lang Abstract Epoxidation of p -benzoquinone bis(ethylene acetal) (1) with m -chloroperbenzoic acid or hydrogen peroxide/benzonitrile afforded corresponding monoepoxide 2, which was converted into p -benzoquinone mono(ethylene acetal) monoepoxide 5 with perchloric acid. Dihydroxylation of 1 with osmium tetroxide or ruthenium trichloride/sodium periodate afforded corresponding cis -diol 6, which was subsequently acetylated to give diacetate 7. One ethyleneacetal moiety in 7 could be selectively hydrolyzed with silica gel/ferric chloride under solvent-free conditions to give ketone 8, which, upon reduction with sodium borohydride and subsequent acetylation of the formed alcohol group, afforded two diastereomeric triacetates 10. Hydrolysis of the remaining acetal functions in the two diastereomers 10, followed by reduction of the second carbonyl group as described above, afforded racemic conduritol C and meso -conduritol D tetraacetates 12 and 13, respectively. Enzymatic resolution of the racemic arabino -configured triacetate 10 with Lipozym failed, while the ribo -configured counterpart reacted smoothly to give enantiomerically pure D - ribo - and L - ribo -configured triacetates 10. The latter pair of enantiomerically pure triacetates were converted into both enantiomers of conduritol C tetraacetate 13 as described for the racemic compounds. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Novel synthesis of flavour quality , -lactonesFLAVOUR AND FRAGRANCE JOURNAL, Issue 3 2006Dhananjay D. Zope Abstract The cyclization of 3-alkenoic acids with 80% sulphuric acid in the synthesis of , -lactones is always associated with fumes of sulphur dioxide gas and traces of cyclopentenones. The cyclopentenones formed during the reaction give off-odours to the , -lactones formed. Two catalysts, p -toluene sulphonic acid and o -phosphoric acid, with a catalytic amount of perchloric acid, were tried in the lactonization reaction to obtain , -lactones in high yields, and the reaction was free from sulphur dioxide gas fumes and cyclopentenones. A comparison of these catalysts with 80% sulphuric acid in the synthesis of , -lactones was also made. Copyright © 2006 John Wiley & Sons, Ltd. [source] Kinetics and mechanism of oxidation of 2-mercaptosuccinic acid by bis(,-oxo)- manganese(III,IV)-cyclam complex in aqueous medium: Influence of externally added copper(II)INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2004Nizamuddin Shaikh Kinetic studies on the oxidation of 2-mercaptosuccinic acid by dinuclear [Mn2III/IV(,-O)2(cyclam)2](ClO4)3] (1) (abbreviated as MnIII,MnIV) (cyclam = 1,4,8,11-tetraaza-cyclotetradecane) have been carried out in aqueous medium in the pH range of 4.0,6.0, in the presence of acetate buffer at 30°C by UV,vis spectrophotometry. In the pH region, two species of complex 1 (MnIII,MnIV and MnIII,MnIVH, the later being ,-O protonated form) were found to be kinetically significant. The first-order dependence of the rate of the reactions on [Thiol] both in presence and absence of externally added copper(II) ions, first-order dependence on [Cu2+] and a decrease of rate of the reactions with increase in pH have been rationalized by suitable sequence of reactions. Protonation of ,-O bridge of 1 is evidenced by the perchloric acid catalyzed decomposition of 1 to mononuclear Mn(III) and Mn(IV) complex observed by UV,vis and EPR spectroscopy. The kinetic features have been rationalized considering Cu(RSH) as the reactive intermediate. EPR spectroscopy lends support for this. The formation of a hydrogen bonded outer-sphere adduct between the reductant and the complex in the lower pH range prior to electron transfer reactions is most likely to occur. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 170,177 2004 [source] Oxidative behavior and relative reactivities of some unsaturated compounds towards hexachloroiridate(IV) in perchloric acid mediumINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 7 2002Kalyan K. Sen Gupta The kinetics of the oxidation of styrene, cinnamic acid, and some of their substituted derivatives by hexachloroiridate(IV) in dimethyl formamide,water mixtures and in the presence of perchloric acid have been investigated. The reactions appear to proceed via the formation of an unstable intermediate 1:1 complex between iridium(IV) and the substrate, followed by the decomposition of the complex in the rate-determining step. Correlation with , yielded , values of ,4.0 and ,3.5 which suggests the formation of a cationic intermediate in the rate-determining step of the reaction. Subsequent cleavage of the carbon,carbon bond yielded the product aldehydes. Thermodynamic and activation parameters associated with the equilibrium and the rate-determining steps were also evaluated. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 411,417, 2002 [source] Accumulation of methylglyoxal in the gingival crevicular fluid of chronic periodontitis patientsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 4 2003S. Kashket Abstract Background, aims: Methylglyoxal (MG), a toxic product of cellular metabolism, is elevated in tissues and fluids in a number of human diseases. A cross-sectional study was undertaken to determine whether MG accumulates in the gingival crevicular fluid (GCF) of chronic periodontitis patients. Methods: GCF samples were collected for 30 s each from three teeth with pocket depths greater than 3 mm (DD sites), from 14 chronic periodontitis patients. Control samples were taken from three healthy sites (DH sites) in the same patients, as well as from seven subjects who were periodontally healthy (HH sites). Fluid volumes were determined and the strips were placed in 0.5 N perchloric acid. Subsequently, samples were derivatized with o -phenylenediamine and the resulting methylquinoxaline was assayed by high-performance liquid chromatography on Lichrospher® -100 RP-18, with UV detection. Results: Mean pocket depths were 5.7±0.7, 2.7±0.6 and 2.7±0.5 mm (mean±SD) for the DD, DH and HH sites, respectively. Mean MG levels were found to be 208.7±241.7 and 142.9±235.7 pmol/site in the GCF from DD and DH sites, respectively (p=0.0023), but only 11.5±4.4 pmol/site for the HH sites. Bacteroides forsythus has been found to accumulate high levels of MG in culture (unpublished data) and, consistent with this, the sampled diseased sites contained higher levels of B. forsythus than the corresponding healthy sites (2.7±4.2×105 versus 0.7±1.1×105, respectively; p=0.022). Total "red complex" microorganisms were significantly elevated in the DD sites. Conclusions: In view of the known protein- and DNA-modifying effects of MG, the finding of elevated levels of MG in the GCF from chronic periodontitis patients supports the hypothesis that MG may contribute to destructive tissue damage in this disease. Zusammenfassung Hintergrund: Methylglyoxal (MG), ein toxisches Produkt des Zellstoffwechsels, ist bei einer Reihe menschlicher Erkrankungen in Geweben und Körperflüssigkeiten erhöht. Zielsetzung: Querschnittsstudie zur Klärung der Frage, ob sich MG in der Sulkusflüssigkeit (SF) bei Patienten mit chronischer Parodontitis ansammelt. Methoden: Bei 14 Patienten mit chronischer Parodontitis wurde SF für 30 s an 3 Zähnen mit Sondierungstiefen >3 mm (DD-Stellen) gewonnen. Kontrollproben wurden von jeweils 3 gesunden Stellen (DH-Stellen) bei den gleichen Patienten und bei 7 parodontal gesunden Personen gewonnen (HH-Stellen). Die Flüssigkeitsvolumina wurden bestimmt und die Probenstreifen in 0,5 N Perchlorsäure gegeben. Anschließend wurden die Proben mit o-Phenyldiamin versetzt und das resultierende Methylquinoxalin wurde mittels High-Performance-Liquid-Chromatographie in einem Lichrospher®-100 RP-18 bei UV-Detektion nachgewiesen. Ergebnisse: Die mittleren Sondierungstiefen lagen bei 5,7±0,7, an den DD-Stellen, bei 2,7±0,6 (DH) und 2,7±0,5 mm (Mittelwert + Standardabweichung) (HH). Die mittleren MG-Spiegel lagen bei 208,7±241,7 an den DD-Stellen und bei 142,9±235,7 pmol/Stelle an den DH-Stellen (p=0,0023), aber nur bei 11,5±4,4 pmol/Stelle an den HH-Stellen. Es war gezeigt worden, dass Bacteroides forsythus in Kultur hohe Konzentrationen von MG ansammelt (unveröffentlichte Daten) und übereinstimmend damit wurden an den untersuchten DD-Stellen höhere Zahlen von B. forsythus gefunden als an den entsprechenden gesunden Stellen (2,7±4,2×105 versus 0,7±1,1×105; p=0,022). Die Zahl aller Keime des "Roten Komplexes" waren an DD-Stellen signifikant erhöht. Schlussfolgerungen: In Anbetracht der bekannten Proteine und DNS verändernden Effekte von MG unterstützt dieser Nachweis erhöhter MG-Spiegel in der SF bei Patienten mit chronischer Parodontitis die Hypothese, dass MG zur Gewebezerstörung bei Parodontitis beiträgt. Résumé Références et buts: Le méthylglyoxal (MG), un produit toxique du métabolisme cellulaire est retrouvé en quantitéélevée dans les tissus et les fluides lors de nombreuses maladies humaines. Une étude croisée fut réalisée pour déterminer si MG s'accumulait dans le fluide gingival (GCF) des patients atteints de parodontite chronique. Méthodes: Des échantillons de GCF furent prélevés pendant 30 secondes chacun de 3 dents avec des profondeurs de poches de plus de 3 mm (sites DD), chez 14 patients atteints de parodontites chroniques. Des échantillons contrôles furent prélevés sur des sites sains (sites DH) chez les mêmes patients, et aussi chez 7 sujets au parodonte sain (sites HH). Les volumes de fluide furent déterminés et les bandelettes ont été mises dans 0.5 N d'acide perchlorique. Puis, les échantillons furent transformés à l'aide de o-phenylenediamine et la méthylquinoxaline ainsi créée fut analysé par chromatographie liquide à haute performance sur une Lichrospher®-100 RP-18, avec détection aux UV. Résultats: Les profondeurs de poche moyenne étaient de 5.7 ± 0.7, 2.7 ± 0.6 et 2.7±0.5 mm (moyenne ± SD) pour les sites DD, DH et HH, respectivement. Les niveaux moyen de MG étaient de 208.7±241.7 et 142.9±235.7 pmol/site dans le fluide des sites in DD et DH, respectivement (p=0.0023), mais seulement de 11.5±4.4 pmol/site pour les sites HH. On a trouvé que Bacteroides forsythus accumulait de hauts niveaux de MG en culture (données non publiées) et les sites malades échantillonnés contenait effectivement de plus hauts niveaux de B. forsythus que les sites sains correspondants (2.7±4.2×105 contre 0.7±1.1×105, respectivement; p=0.022). Les microorganismes du complexe rouge étaient significativement en nombre élevé dans les sites DD. Conclusions: Au vu des effets connus de MG pour modifier les protéines et l'AND, la découverte de niveaux élevés de MG dans le fluide gingival de patients atteints de maladie parodontale chronique supporte l'hypothèse selon laquelle MG pourrait contribuer aux dommages tissulaires destructifs rencontrés au cours de cette maladie. [source] Fluorescent behavior of 2-(3,4,5,6-tetrafluoro-2-hydroxyphenyl)imidazo-[1,2- a]pyridine in the presence of metal perchlorateJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2007Kiyoshi Tanaka 2-(3,4,5,6-Tetrafluoro-2-hydroxyphenyl)imidazo[1,2- a]pyridine (1) emits long wavelength light around 540 nm both in polar and in nonpolar solvents. Zn2+ perchlorate in acetonitrile causes the intermediate wavelength emission around 430 nm, which is ascribed to the species where the imidazole nitrogen atom and the phenolate oxygen atom bridge Zn2+. In the presence of Hg2+ and Al3+ perchlorates, short wavelength emission around 370 nm is strongly increased and this fluorescent enhancement is attributable not to the coordination of Hg2+ and Al3+ to 1 but to the formation of the salt of perchloric acid of 1. [source] Synthesis of tritium- and deuterium-labeled budesonideJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 1 2008Bachir Latli Abstract Tritium-labeled budesonide was prepared by the selective reduction of a double bond in the butenylenedioxy side chain using carrier-free tritium and palladium on carbon as a catalyst in absolute ethanol. Although the reduction gave a mixture of the desired product and the expected byproducts resulting from over reduction of the other double bonds in ring A, the desired tritium-labeled budesonide was easily isolated by reverse phase HPLC and with specific activity of 54,Ci/mmol. [D8]-budesonide was prepared from 16,-hydroxyprednisolone and D8 -butyraldehyde in 1,4-dioxane in the presence of perchloric acid. The isotopic enrichment was found to be more than 99,atom% D. Copyright © 2008 John Wiley & Sons, Ltd. [source] Increased vigabatrin entry into the brain by polysorbate 80 and sodium caprateJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 2 2001D. Dimitrijevic The effects of a non-ionic surfactant, polysorbate 80, and the sodium salt of the saturated fatty acid, sodium caprate (C10), as potential brain absorption enhancers for vigabatrin were studied. Vigabatrin is an enzyme-activated irreversible inhibitor of ,-aminobutyric acid (GABA) transaminase that increases brain and cerebrospinal GABA concentrations in animals and man. Before intravenous administration, a range of concentrations of the surfactants were tested using erythrocyte lysis or the red blood cell lysis test to establish the non-toxic concentration range. Vigabatrin was dissolved in 0.1% polysorbate 80 and 0.1% sodium caprate and administered intravenously in doses of 4 mL kg,1 to male Wistar rats (230,250 g; n = 3). Rats were killed 2 h after drug and surfactant administration and the brains were immediately removed and homogenized in 0.4m perchloric acid. Selected ion monitoring electrospray mass spectrometry was used to determine the concentration of vigabatrin and GABA directly from the perchloric acid extract of the rat brain. This method was developed to increase the speed and efficiency of the analysis by removing the need for complex extraction and derivatization procedures while retaining the specificity of the mass spectrometer as a detector. The stability of both vigabatrin and GABA in perchloric acid was established by monitoring their pseudo molecular ions in standard solutions at timed intervals over 24 h. Although the detection level for vigabatrin and GABA was at least 50 pg, only GABA was detected in rat brain. Vigabatrin caused a small increase in whole brain GABA. However, GABA levels were higher in the samples with vigabatrin + enhancer than in the samples where vigabatrin alone was administered. One-way analysis of variance indicated a significant effect of the surfactants on GABA levels (F (5,17) = 11.86, P < 0.01) and vigabatrin absorption was presumed. The rectal temperature of the rats is lowered by the presence of vigabatrin in the brain. Vigabatrin alone decreased rectal temperature by 6%. When given with either polysorbate 80 or sodium caprate, the extent of temperature lowering was significantly greater (P < 0.001). There was no significant difference after 2 h between polysorbate 80 + vigabatrin, and sodium caprate + vigabatrin. [source] Feasibility of the spontaneous gas-phase proton transfer equilibria between neutral Brønsted acids and Brønsted basesJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 7-8 2008Peeter Burk Abstract The computational investigation of interactions of different acid,base pairs regarding the nature and extent of spontaneous proton transfer was carried out at B3LYP/6-311,+,G** level. The selected acid,base pairs include the interactions of strong base (K2O) with acids of different strength (HClO4, HCl, and HF), and strong acid (HClO4) with bases ranging from K2O (GB,=,322.8,kcal/mol) to H2O (GB,=,157.6,kcal/mol). It was shown that spontaneus, unassisted proton transfer can take place in the gas-phase reactions of strong neutral Brønsted acids and bases. The reaction might be barrierless as in case of interactions between strong acids and bases, for example perchloric acid and alkali metal oxides or potassium oxide and halogen hydrides, or involve the encounter complex (hydrogen bonded acid,base cluster), which is separated from ion-pair by the transition state. Copyright © 2008 John Wiley & Sons, Ltd. [source] Acid-catalyzed hydrolysis of bridged bi- and tricyclic compounds.JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 9 20023-acetylnortricyclanes, Kinetics, XXXIX, mechanisms of the hydration reactions of 1- Abstract The disappearance of 1- and 3-acetylnortricyclanes (1-Ac and 2-Ac) in aqueous perchloric acid was followed by capillary gas chromatography at different temperatures and acid concentrations. 1-Ac is much less reactive than 2-Ac. The activation parameters, solvent deuterium isotope effects and parameters of excess acidity equations were measured and the products studied. 1-Acetylnortricyclane is hydrated according to the A -2 mechanism, i.e. the carbonyl oxygen is protonated in the fast pre-equilibrium and one water molecule attacks at the rate-limiting stage the partially open cyclopropane ring, producing 6-acetyl-2-norborneols. 3-Acetylnortricyclane is hydrated according to the AdE2 mechanism, i.e. the cyclopropane ring is slowly protonated and opened, with subsequent fast attack of water producing 3-, 5- and 7-acetyl-2-norborneols. Copyright © 2002 John Wiley & Sons, Ltd. [source] Acid-catalyzed hydrolysis of bridged bi- and tricyclic compounds.JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 12 20013-nortricyclanols, Kinetics, XXXVIII, mechanisms of 1- Abstract The disappearance of 1- and 3-nortricyclanols (1-OH and 2-OH) in aqueous perchloric acid was followed by capillary GC at different temperatures and acid concentrations. 1-OH is ca 1000 times more reactive than 2-OH. The activation parameters, solvent deuterium isotope effects and parameters of excess acidity equations were measured and the products were studied. Both isomeric nortricyclanols react according to the AdE2 mechanism, i.e. the cyclopropane ring is protonated at the rate-determining stage of the reaction. The protonation causes, in the case of 1-OH, an isomerization called homoketonization with 2-norbornanone as the only product and, in the case of 2-OH, hydration, i.e. the formation of hydroxyl-substituted norbornyl cations, the fast attack of which by water produces several norbornanediols. Copyright © 2001 John Wiley & Sons, Ltd. [source] Instrumental planar chromatographic method for determination of carbamazepine in human serumJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2009Sigrid Mennickent Abstract An instrumental planar chromatographic (HPTLC) method for quantification of carbamazepine in human serum was developed using liquid-liquid extraction with dichloromethane, fluorescence activation with perchloric acid 60%/ethanol/water (1:1:1, v/v) and fluorescence detection. Planar chromatographic separation was performed on precoated silica gel F254 HPTLC plates using a mixture of ethyl acetate/toluene/methanol/acetic acid glacial (5:4:0.5:0.5, v/v) as mobile phase. Densitometric detection was done at 366 nm. The method was validated for linearity, precision and accuracy. Linear calibration curves in the range of 3 and 20 ng/,L showed correlation coefficient of 0.998. The intra-assay and inter-assay precision, expressed as the RSD, were in the range of 0.41,1.24% (n = 3) and 2.17,3.17% (n = 9), respectively. The LOD was 0.19 ng, and the LOQ was 0.57 ng. Accuracy, calculated as percentage recovery, was between 98.98 and 101.96%, with a RSD not higher than 1.52%. The method was selective for the active principle tested. In conclusion, the method is useful for quantitative determination of carbamazepine in human serum. [source] A theoretical explanation for the retention mechanism of ion exclusion chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2003Bronis, aw K. G Abstract Ion Exclusion Chromatography is classically used for the separation of weak acid anions. Dilute strong acids (e.g. sulphuric or perchloric acid) or just water are used as eluents. To increase the exclusion effect, strong cation exchangers, characterized by high concentration of functional groups, are applied. The inner column volume of commercially available columns is increased by increasing their size in comparison to traditional ones (usually 300×7.8 mm ID). The description of the retention mechanism of this technique implicitly assumes that both mobile and stationary phases are typical aqueous solutions, and their dielectric constants are thus equal. This equality implies the equality of solute dissociation constants in both phases. Another implicit assumption is that the dead- and inner volumes of the column are constant, and independent of the mobile phase composition. The present paper shows that stationary and mobile phases are generally characterized by different physicochemical parameters. Thus, they cannot be considered as regular aqueous solutions. Additionally, we show that weak cation exchanger resins, which are characterized by a relatively small concentration of the functional groups, and weak acid based buffers can also be used in IEC. This would expand the possible applications of this method and enable, for example, the separation of strong acids (anions). The influence of ionic strength on the retention and dead- and inner column volumes is also discussed. Finally we also briefly describe the retention mechanism of Electrostatic Ion Chromatography. [source] A fluorimetric method for the determination of trace pentachlorophenol, based on its inhibitory effect on the redox reaction between the improved Fenton reagent and rhodamine BLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 5 2007Huiqin Guo Abstract A sensitive fluorimetric method is presented and discussed for the determination of pentachlorophenol in aqueous solutions. This method is based on the inhibitory effect of pentachlorophenol on the reaction of conventional Fenton [Fe(III) + H2O2] reagent with rhodamine B in the medium of perchloric acid, which results in the fluorescence quenching of rhodamine B. It was further found that the sensitivity for the determination was improved significantly when the molecular ligand EDTA was added. This improved system was therefore presented for the determination of pentachlorophenol. The characteristics of the excitation and emission spectra, optimization of the experimental conditions, the stability of the system and the influence of foreign matter have all been investigated. Under optimal conditions, the linear range for the determination of pentachlorophenol is 12,480 ng/mL with a 3, limit of detection of 0.96 ng/mL. Compared with the conventional Fenton system, the improved system shows obvious advantages in both sensitivity and selectivity. By combination with the pretreatment of samples using ion exchange resins and XDA-1 absorption resin, the improved Fenton method was used for the first time for the determination of pentachlorophenol in synthetic samples and natural water samples, and satisfactory results, in agreement with those of the HPLC method, were achieved. The possible mechanism of the reactions has also been discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Co-determination of ATP and proteins in Triton X 100 non-ionic detergent-opened monolayer cultured cellsLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 5 2007Tamás K, szegi Abstract Human monolayer cells (HEp-2 and Hep G2) were cultured in 96-well plates. A modified Triton X 100 nonionic detergent extraction method was used for releasing intracellular ATP and protein in one step. The detergent technique was compared to perchloric acid (PCA) extraction. ATP was determined by the firefly bioluminescence method and ATP values were referred to cell protein (ATP:protein ratio). There was no significant difference in ATP data between detergent and PCA treatments. The ATP:protein ratio seems to be a sensitive tool for characterizing the metabolic activity of monolayer tissue culture cells. The protein-mobilizing capability of Triton X 100 depends on the type of cell culture used. Our modified extraction gives reliable ATP:protein values with one simple extraction step. Copyright © 2007 John Wiley & Sons, Ltd. [source] Brain GABA editing by localized in vivo1H magnetic resonance spectroscopyNMR IN BIOMEDICINE, Issue 2 2004G. Bielicki Abstract Editing of GABA by 1H MRS in a specific brain area is a unique tool for in vivo non-invasive investigation of neurotransmission disorders. Selective GABA detection is achieved using sequences based on double quantum coherence (DQC). Our pulse sequence makes accurate measurements without artefacts due to spatial localization. The sequence was tested on a phantom solution. The effect of vigabatrin, a specific inhibitor of GABA transaminase, was measured in rat brain and GABA detection was performed in vivo in monkey brain using this procedure. Rats were spilt into two groups. In the control group, the rats had access to water and, in the other group (vigabatrin, VGB, rats), animals were allowed free access to drinking water containing vigabatrin. After 3 weeks of treatment, rats were anesthetized for in vivo NMR spectroscopy investigation. At the end of the experiment, brains were quickly removed, freeze-clamped and extracted with 4% perchloric acid. One part of the acid extract was used for GABA concentrations assessment by ion exchange chromatography with ninhydrin detection. The second was used for high-resolution NMR analysis. By chromatography measurements, the GABA concentration was 1.23±0.06,,mol/g for controls, while for vigabatrin-treated rats the GABA concentration was 4.89±1.60,,mol/g. The NMR in vivo results were closely correlated with the NMR ex vivo (r=0.99, p<0.01) and chromatography results (r=0.98, p<0.01). The correlation between ex vivo results and chromatography results was also high (r=0.99, p<0.001). This pulse sequence performed GABA editing from a 376,,l voxel located on the right basal ganglia area in a non-human primate brain. This in vivo GABA editing scheme can thus be proposed for accurate measurement of brain GABA concentrations. Copyright © 2004 John Wiley & Sons, Ltd. [source] Redetermination of hydronium perchlorate at 193 and 293,KACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2003Azhar A. Rahman A sample of hydronium perchlorate, H3O+·ClO4,, crystallized from ethanol at ambient temperature, was found to be orthorhombic (space group Pnma) at both 193 and 293,K, with no phase transition observed in this temperature range. This contrasts with the earlier observation [Nordman (1962). Acta Cryst. 15, 18,23] of a monoclinic phase (space group P21/n) at 193,K for crystals grown at that temperature from perchloric acid. The hydronium and perchlorate ions lie across a mirror plane but it is not possible to define at either temperature a simple description of the H-atom positions due to the three-dimensional tumbling of the hydronium cation. [source] Fluoride content of powdered infant formula meets Australian Food Safety StandardsAUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH, Issue 6 2009Helen Clifford Abstract Objectives: To identify the fluoride content of powdered formula for infants 0-12 months in products available from Brisbane stores in 2006/07 and compare this with the fluoride content of infant formula products available in Australia 10 years earlier. Methods: A range of available infant formula powders were collected from major supermarkets and chemists in Brisbane, Queensland. The fluoride levels in infant formula powder samples were determined using a modification of the micro-diffusion method of Silva and Reynolds1 utilising perchloric acid and silver sulphate and measured with an ion selective (fluoride) electrode/meter. Fluoride content both prior to and after reconstitution, as well as estimated daily intake according to age was calculated. Results: Formula samples contained an average of 0.49 ,g F/g of powder (range 0.24,0.92 ,g F/g). After reconstitution with water containing 0mg/L fluoride, the fluoride content averaged 7.09,g F/100mL (range 3.367,22.72 ,g F/100mL). Estimated infant fluoride intakes ranged from 0.0039 mg/kg/day for a 6-12 month old infant when reconstituting milk-based formula with non-fluoridated water (0 mg/L), to 0.1735 mg/kg/day for a 0-3 month old infant when reconstituting soy-based formula with fluoridated water (1.0 mg/L). Conclusions: Infant formula powders contain lower levels of fluoride than previously found in Australia in 1996. Implications: This confirms that infants consume only a small amount of fluoride from milk-based powdered infant formula. Although soy-based infant formulas contain more fluoride than milk-based products, the levels still comply with national food standards. [source] Determination of serotonin, melatonin and metabolites in gastrointestinal tissue using high-performance liquid chromatography with electrochemical detectionBIOMEDICAL CHROMATOGRAPHY, Issue 2 2009Rosanna M. W. Chau Abstract In this paper we show a simple isocratic chromatographic method for the detection of serotonin and its precursors and metabolites from various types of gastrointestinal tissue. The paper measures for the first time basal measurements of melatonin in the gastrointestinal tract, which has recently been shown to be released from the musosal lining of the gut. Tissue samples were stable following sample preparation in either 0.1 m perchloric acid or mobile phase. Analysis was carried out using a mobile phase consisting of 10% acetonitrile,90% acetate acid buffer pH 4.0 with 2 mm decane,sulfonic acid sodium salt at a column temperature of 50°C. Electrochemical detection was utilized at a potential of +850 mV vs Ag/AgCl reference electrode at 10 µA full-scale deflection. The detection limit of 5-HT and melatonin was 241 and 308 nm respectively for a 10 µL injection. As a result of the method optimization, total analysis was reduced to 30 min. Accurate responses of the tissue samples following sample preparation could be obtained following a week after storage at ,80°C. This method is capable of preparing and analysing of samples from all regions of the gastrointestinal tract. Copyright © 2008 John Wiley & Sons, Ltd. [source] Rapid quantification of lisinopril in human plasma by liquid chromatography/tandem mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 4 2007Weiwei Qin Abstract An assay based on protein precipitation and liquid chromatography/tandem mass spectrometry (LC-MS/MS) has been developed and validated for the quantitative analysis of lisinopril in human plasma. After the addition of enalaprilat as internal standard (IS), plasma samples were prepared by one-step protein precipitation using perchloric acid followed by an isocratic elution with 10 mm ammonium acetate buffer (pH adjusted to 5.0 with acetic acid),methanol (70:30, v/v) on a Phenomenex Luna 5µC18 (2) column. Detection was performed on a triple-quadrupole mass spectrometer utilizing an electrospray ionization (ESI) interface operating in positive ion and selected reaction monitoring (SRM) mode with the precursor to product ion transitions m/z 406,246 for lisinopril and m/z 349,206 for enalaprilat. Calibration curves of lisinopril in human plasma were linear (r = 0.9973,0.9998) over the concentration range 2,200 ng/mL with acceptable accuracy and precision. The limit of detection and lower limit of quantification in human plasma were 1 and 2 ng/mL, respectively. The validated LC-MS/MS method has been successfully applied to a preliminary pharmacokinetic study of lisinopril in Chinese healthy male volunteers. Copyright © 2007 John Wiley & Sons, Ltd. [source] Simple determination of pirfenidone in rat plasma via high-performance liquid chromatographyBIOMEDICAL CHROMATOGRAPHY, Issue 12 2006Yongsheng Wang Abstract A simple, rapid and reliable high-performance liquid chromatographic method was developed and validated for the determination of pirfenidone and its major metabolites in rat plasma. Plasma proteins were precipitated with perchloric acid (10%, v/v) and the supernatant after centrifugation was determined using high-performance liquid chromatography. The analysis was carried out on a Lichrospher C18 column (250 × 4.6 mm i.d., 5 µm). The mobile phase consisted of acetonitrile,water containing 0.2% acetic acid (23:77, v/v) at a flow-rate of 1 mL/min. The eluant was detected at 310 nm. The calibration curves were linear over a concentration range from 0.15 to 76.67 µg/mL. The accuracy (relative error) of the assay ranged from -2.6 to 7.9% and the precision (coefficient of variation) was less than 4.5%. The established method has been successfully applied to a pharmacokinetic study of pirfenidone following a single oral dose to rats. Copyright © 2006 John Wiley & Sons, Ltd. [source] A simple and simultaneous determination of acyclovir and ganciclovir in human plasma by high-performance liquid chromatographyBIOMEDICAL CHROMATOGRAPHY, Issue 8 2003Daisuke Teshima Abstract A simple high-performance liquid chromatographic method was developed for the simultaneous determination of the therapeutic levels of acyclovir and ganciclovir in human plasma. After precipitation of plasma proteins with 6% perchloric acid, acyclovir and ganciclovir were simultaneously determined by reversed-phase chromatography with spectophotometric detection at 254 nm. The peak heights for acyclovir and ganciclovir were linearly related to their concentrations ranging from 0.063 to 2.080 µg/mL. The recovery was 100.48,102.84% for acyclovir and 99.26,103.07% for ganciclovir. The intra- and inter-day relative standard deviation values were in the range 0.186,8.703% for acyclovir and 0.137,6.424% for ganciclovir. The detection limits for both compounds were 0.01 µg/mL determined as the signal-to-noise ratio of 3. The present method is applicable to therapeutic monitoring during antiviral medication. Copyright © 2003 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||