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At least 91 records · Page 5Linked to original sources
PubMed2005

Pd(II)-catalysed and Hg(II)-co-catalysed oxidation of D-glucose and D-fructose by N-bromoacetamide in the presence of perchloric acid: a kinetic and mechanistic study.

The kinetics of Pd(II)-catalysed and Hg(II)-co-catalysed oxidation of D-glucose (Glc) and D-fructose (Fru) by N-bromoacetamide (NBA) in the presence of perchloric acid using mercury(II) acetate as a scavenger for Br- ions have been studied. The results show first-order kinetics with respect to NBA at low concentrations, tending to zero order at high concentrations. First-order kinetics with respect to Pd(II) and inverse fractional order in Cl- ions throughout their variation have also been noted. The observed direct proportionality between the first-order rate constant (k1) and the reducing sugar concentration shows departure from the straight line only at very higher concentration of sugar. Addition of acetamide (NHA) decreases the first-order rate constant while the oxidation rate is not influenced by the change in the ionic strength (mu) of the medium. Variation of [Hg(OAc)2] shows a positive effect on the rate of reaction. The observed negative effect in H+ at lower concentrations tends to an insignificant effect at its higher concentrations. The first-order rate constant decreases with an increase in the dielectric constant of the medium. The various activation parameters have also been evaluated. The products of the reactions were identified as arabinonic acid and formic acid for both the hexoses. A plausible mechanism involving HOBr as the reactive oxidising species, Hg(II) as co-catalyst, and [PdCl3.S]-1 as the reactive Pd(II)-sugar complex in the rate-controlling step is proposed.

Acetamides↗
PubMed1982

Fluorimetric determination of biogenic 5-hydroxy- and 5-methoxyindoles by high-performance liquid chromatography using perchloric acid as post-column reagent.

A method for the determination of biogenic 5-hydroxy- and 5-methoxyindoles using high-performance liquid chromatography with fluorescence detection was developed. The specific fluorescence of these indoles induced by perchloric acid was utilized as the post-column detection system. The determination limits were 3 pmol for 5-hydroxy-L-tryptophan and 5 pmol for serotonin (5-HT) and 5-hydroxyindole-3-acetic acid (HIAA). The method was applied to the determination of 5-HT and HIAA in rat brain tissues using 5-hydroxygramine as the internal standard.

Animals↗
PubMed1995

Application of a new perchloric acid treatment method to measure endotoxin by an endotoxin-specific chromogenic Limulus test in neonatal septicemia.

The endotoxin in blood was measured to establish both the cut-off value and to detect Gram-negative septicemia. We employed a new perchloric acid treatment method using an endotoxin-specific chromogenic Limulus test (Endospecy test). The cut-off value of endotoxin in blood was 11.2 pg/mL. All cases of septicemia (n = 7) showed high values of endotoxin. Three cases were Group B streptococci, and two cases were Escherichia coli. The others were showed to be negative in blood cultures. The paired values of endotoxin titers during a 48 h interval were useful to evaluate the effectiveness of antibiotics.

Bacteremia↗
PubMed1982

Perchloric acid treatment of human blood for quantitative endotoxin assay using synthetic chromogenic substrate for horseshoe crab clotting enzyme.

A new reliable human blood treatment was established for quantitative endotoxin assay using synthetic chromogenic substrate [Boc-Leu-Gly-Arg-rho-nitroanilide]. Addition of perchloric acid in a final concentration of 1.25% to platelet-rich plasma or serum in a 2:1 volume ratio completely eliminated nonspecific amidase activities as well as inhibitors. By this method, the recovery of added endotoxin was nearly 100%, and was almost independent of sample dilutions and anticoagulants.

Amidohydrolases↗
PubMed2006

Analysis of the changes in the 1H NMR spectral pattern of perchloric acid extracts of C6 cells with growth.

The aim of this work was to identify spectral markers of cell proliferation that could be of use in clinical MRS. Cultured C6 ATCC rat glioma cells were used as models for this purpose and metabolites were extracted with perchloric acid at three different growth curve stages: log, confluence and post-confluence. 1D and 2D in vitro(1)H NMR spectra were recorded at 9.4 T. Statistically significant changes in myo-inositol and glutamine concentrations between log phase and post-confluence were found when normalized to the creatine ratio. The myo-inositol/creatine ratio was 2.76 +/- 0.82 at log phase increasing to 7.43 +/- 1.34 at post-confluence, while the glutamine/creatine ratio decreased from 0.22 +/- 0.03 to 0.10 +/- 0.02. No significant differences were recorded for other metabolites investigated. The fact that both myo-inositol and glutamine are detectable by in vivo MRS at clinical fields makes their changes relevant as potential astrocytic tumour proliferation rate markers in clinical MRS.

Animals↗
PubMed2006

Oxidation of adsorbed CO on Pt(111) in CO-saturated perchloric acid aqueous solutions: simultaneous in situ time-resolved reflectance spectroscopy and second harmonic generation studies.

Simultaneous normalized differential reflectance spectroscopy (DeltaR/R) and second harmonic generation (SHG) has been employed to follow, independently, OH and adsorbed CO (CO(ads)) on a single Pt(111) microfacet in CO-saturated aqueous perchloric acidic solutions during voltammetric cycles, leading to the oxidation of CO(ads) and subsequent readsorption of CO on the surface. The results obtained are consistent with the disruption of the radical19 x radical19R19.1 degrees phase just prior to the oxidation of adsorbed CO.

Letter↗
PubMed1996

Application of a new perchloric acid treatment method to measure endotoxin in both amniotic fluid and cord blood by an endotoxin-specific chromogenic Limulus test in intra-amniotic infection.

Endotoxin in both amniotic fluid and cord blood was measured to detect intra-amniotic fetal infection. Both amniotic fluid and cord blood plasma were pretreated by a perchloric acid treatment, and the endotoxin level was measured by Endospecy test. Cut off values for endotoxin in amniotic fluid and cord blood were 8.5 pg/mL and 7.6 pg/mL, respectively. Escherichia coli intra-amniotic infection caused respiratory distress syndrome (RDS)-mimicking pneumonia. Abnormally high values of endotoxin in both amniotic fluid and cord blood were detected. Intra-amniotic infection caused by Gram-positive bacteria (group B streptococci, Enterococcus fecalis) was shown to be endotoxin negative in both amniotic fluid and cord blood. In cases of negative amniotic fluid culture, measurement of the value of endotoxin in the amniotic fluid is useful in identifying intra-amniotic fetal infection.

Amniotic Fluid↗
PubMedDate not supplied

Perchloric acid, toxicolor, endospecy, and miconazole in the early diagnosis and treatment of fungemia.

As a procedure for the diagnosis of fungemia, Toxicolor and Endospecy (limulus tests using a synthetic chromogenic substrate) were used to measure (1----3)-beta-D-glucan (beta-glucan), which is a membranous component of fungus. The plasma samples were pretreated with a new perchloric acid method. These methods permit measurement of the beta-glucan within about two hours. Patients in whom fungemia was diagnosed were effectively treated with miconazole.

Adult↗
PubMed2004

Dehydrogenation versus oxygenation in two-electron and four-electron reduction of dioxygen by 9-alkyl-10-methyl-9,10-dihydroacridines catalyzed by monomeric cobalt porphyrins and cofacial dicobalt porphyrins in the presence of perchloric acid.

Dehydrogenation of 10-methyl-9,10-dihydroacridine (AcrH(2)) by dioxygen (O(2)) proceeds efficiently, accompanied by the two-electron and four-electron reduction of O(2) to produce H(2)O(2) and H(2)O, which are effectively catalyzed by monomeric cobalt porphyrins and cofacial dicobalt porphyrins in the presence of perchloric acid (HClO(4)) in acetonitrile (MeCN) and benzonitrile (PhCN), respectively. The cobalt porphyrin catalyzed two-electron reduction of O(2) also occurs efficiently by 9-alkyl-10-methyl-9,10-dihydroacridines (AcrHR; R = Me, Et, and CH(2)COOEt) to yield 9-alkyl-10-methylacridinium ion (AcrR+) and H(2)O(2). In the case of R = Bu(t) and CMe(2)COOMe, however, the catalytic two-electron and four-electron reduction of O(2) by AcrHR results in oxygenation of the alkyl group of AcrHR rather than dehydrogenation to yield 10-methylacridinium ion (AcrH+) and the oxygenated products of the alkyl groups, i.e., the corresponding hydroperoxides (ROOH) and the alcohol (ROH), respectively. The catalytic mechanisms of the dehydrogenation vs the oxygenation of AcrHR in the two-electron and four-electron reduction of O(2), catalyzed by monomeric cobalt porphyrins and cofacial dicobalt porphyrins, respectively, are discussed in relation to the C(9)-H or C(9)-C bond cleavage of AcrHR radical cations produced in the electron-transfer oxidation of AcrHR.

Acridines↗
PubMed1991

Establishment of a new perchloric acid treatment method to allow determination of the total endotoxin content in human plasma by the limulus test and clinical application.

We established a new method of plasma treatment for the removal of interfering factors in the plasma to allow detection of endotoxin by limulus test. The limulus test used was an endotoxin-specific chromogenic test, the Endospecy test. Perchloric acid (PCA) treatment and centrifugation (PCA method) is usually used to remove interfering factors from plasma, with the precipitate being discarded and the supernatant used to detect endotoxin. As the solubilized precipitates of endotoxin-spiked plasma and some patient plasma were found to contain the Endospecy activity, we have devised a new method assaying endotoxin in both the supernatant and precipitate. This study confirmed that the solubilized precipitate of endotoxin-spiked plasma had Endospecy activity and found that the precipitate had other endotoxin activities, such as lethality in galactosamine-sensitized mice and pyrogenicity in rabbits. We also confirmed that interfering factors were completely removed from plasma samples by this new method. The endotoxin level after the new PCA method was found to be about 8 times higher than that determined after PCA treatment and the new PCA method surpasses the conventional PCA method with regard to the positive rate of endotoxin contents in clinical samples. These results indicate that the new PCA method is superior to the PCA method as a plasma pretreatment method for limulus test.

Amidohydrolases↗
PubMed2005

Spectrophotometric determination of uranium with arsenazo-III in perchloric acid.

A short, sensitive and reliable spectrophotometric method, which has advantages over all known "wet chemistry" methods for uranium determination with regard to tolerance to common interferences, has been developed for the determination of uranium. Selectivity, molar absorptivity and the determination range of uranium have been enhanced by using 0.07% arsenazo-III as a chromogenic reagent. The use of 3 mol dm(-3) perchloric acid as a medium of determination was found to be excellent in terms of good solvent compatibility on dilution, destruction of organic contamination and simplicity of operation. The uranium-arsenazo-III complex formed instantly, and was found to be stable for more than 3 weeks with constant absorbance. Beer's law was obeyed up to a uranium concentration of 16 microg g(-1), with a molar absorptivity at 651 nm of 1.45x10(5) mol(-1) dm(3) cm(-1) at 24+/-2 degrees C. Only phosphate and citrate at 70-fold excess over uranium interfere seriously, whereas other anions studied could be tolerated up to a 70-fold excess over uranium. Of the cations studied, only Mn(II), Co(II), Ni(II), Cu(II) and Cr(III) decreased the normal absorbance of the complex. Iron(III), Ce(III) and Y(III) enhanced the absorbance. Other cations studied did not affect the absorbance up to a 50-fold excess. The accuracy was checked by determining uranium from standard solutions in the range 10-50 microg g(-1). It was found to be accurate with a 96.0-98.6% recovery rate. The method has been successfully applied to standard reference materials and ore samples at microg g(-1) levels.

Absorption↗
PubMed1996

A new method for the determination of specific 13C enrichment in phosphorylated [1-13C]glucose metabolites. 13C-coupled, 1H-decoupled 31P-NMR spectroscopy of tissue perchloric acid extracts.

A 31P-NMR method for the determination of 13C enrichment in phosphorylated [1-(13)C]glucose metabolites was developed by taking advantage of the 13C satellites detectable for 31P-NMR signals of metabolites such as UDP-hexoses, UDP-N-acetylhexosamines and other phosphorylated compounds generated during glycolysis and subsequent anabolism. HT-29 cells were incubated in culture medium containing 4.5 g/l [1-(13)C]glucose for 24 h prior to cell extraction, and high-resolution 31P-NMR spectra were acquired from perchloric acid extracts. Since glucose and its phosphorylated products are key metabolites for many different metabolic processes, this method may be very helpful for studying specific metabolic pathways involving phosphorylated glucose metabolites.

Carbon Isotopes↗
PubMed1990

Differences in metabolite content between intact pancreases and their perchloric acid extracts. A 2D 1H/31P correlation NMR study.

Perchloric and hydrochloric acid extracts of intact pancreases from healthy rats and from rats with experimental acute pancreatitis were analysed using 2D 1H/31P correlation NMR spectroscopy. Major differences were found in the 2D maps between the extracts and the intact tissues. In the case of the intact diseased pancreas the prominent 31P signal at the phosphodiester region has been assigned in our previous work as lecithin/taurocholate complex. However, the signal found in the same chemical shift region in extracts of diseased pancreases as well as healthy ones, is identified here as the phosphodiester residue of oligoribonucleotides. In these extracts additional 31P signals were found and assigned as phosphomonoester and phosphodiester hydrolysis products of RNA. The amounts of these compounds, as a function of the acid concentrations were determined, and conditions for their minimization were defined.

Animals↗
PubMed2002

Perchloric acid enhances sensitivity and reproducibility of the ferric-xylenol orange peroxide assay.

The ferrous oxidation in xylenol orange (FOX) assay for hydroperoxides suffers from very narrow pH optimum in the range 1.7-1.8. Most published protocols recommend 25 mM sulfuric acid as the solvent, but this in practice does not ensure the maintenance of correct pH in the presence of materials such as samples of biological origin. Substitution of perchloric for the sulfuric acid resulted in a lowering of the optimum pH of the assay to 1.1, a decreased dependence of the absorbance of the ferric-xylenol orange complex on acid concentration and decreased sensitivity to added compounds. Molar absorption coefficients of hydrogen peroxide, cumene, and butyl hydroperoxides and of hydroperoxide groups generated in oxidized protein and lipids were determined and found to be higher than in sulfuric acid. The optimum concentration of perchloric acid proved to be 110 mM. The new assay was designated as PCA-FOX, to distinguish it from the FOX methods based on sulfuric acid.

Animals↗
PubMed1984

A rapid and safe method of estimating nanomole quantities of P, K+, Na+, Ca2+, and Mg2+ in plant material by perchloric acid digestion.

A method for the determination of nanomole amounts of P and major cations in samples of dried plant tissue is described. Samples weighing 2-7 mg were digested by refluxing tissue in a mixture of perchloric and nitric acids, under conditions which minimized the hazards associated with perchloric acid digestion. In most tissues analyzed, reproducibility between triplicate samples was less than +/- 5%. However, where the amount of P in the tissue was very low (samples contained about 50 nmol P each), the variation between triplicates was greater.

Calcium↗
PubMed2005

Structural investigation of Pd(II) in concentrated nitric and perchloric acid solutions by XAFS.

XAFS spectra of palladium(II) in concentrated HNO3/HClO4 acid mixtures have been recorded and analyzed. Structural parameters of the Pd(H2O)4(2+) complex and the mixed nitric Pd(NO3)2(H2O)2 complex, for the first time, were determined by the XAFS method. For pure 5 M HClO4 and for mixtures (0-0.3 M HNO3), the XAFS spectra of the 0.02 M Pd solutions are indeed very similar and originated from four Pd-O(w) equivalent distances. For the Pd(H2O)4(2+) square-planar aqua ion in strong perchloric acid, the use of an FEFF6 theoretical approach led to a first-shell Pd-O(w) distance of 2.00 (1) A and a Debye-Waller (DW) factor of sigma2 = 0.0030 (3) A2. Four water molecules are tightly bound to the Pd2+ ion in the equatorial plane, while two (or one) axial water molecules are weakly bound to the metal ion at 2.5 A with a DW factor of 0.015 (5) A2. For highly concentrated mixtures (4-6 M HNO3) and for pure concentrated (4-6 M) nitric acid as well as for crystalline powder Pd(NO3)2(H2O)2, the XAFS spectra are very similar and are determined by the mixed nitric complex Pd(NO3)2(H2O)2: four Pd-O near-equivalent distances of 2.01 (1) A from two H2O and two NO3 molecules with a total DW factor of sigma2 = 0.0037 (3) A2. Moreover, two Pd---N distances of 2.8-2.9 A were determined in the second coordination shell. Finally, for intermediate mixtures (1-3 M HNO3 in 5 M HClO4), the XAFS spectra are a superposition of the XAFS of Pd(H2O)4(2+) and Pd(NO3)2(H2O)2 complexes. The mean ligand number NO3(-) around Pd2+ has been calculated, and the XAFS results at pH close to zero confirm the spectrophotometric results previously published.

Journal Article↗