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PubMedDate not supplied

Catalytic wet oxidation of 2,4-dichlorophenol solutions: activity of the manganese-cerium composite catalyst and biodegradability of the effluent stream.

Aqueous solutions containing 100 to 1000 mg/L of 2,4-dichlorophenol (2,4-DCP) were oxidized in an upflowing fixed-bed reactor in this study of manganese-cerium composite catalysts, which were prepared by the coprecipitation of both manganese nitrate and ceric nitrate at various molar concentrations. Results showed that 2,4-DCP conversion by wet oxidation in the presence of the manganese-cerium composite catalysts was a function of the molar ratio of the manganese-cerium catalyst. The kinetic behavior of 2,4-DCP oxidation with catalysis could be explained by using a zero-order rate expression. Total organic carbon (TOC) removal by wet oxidation in the absence of any catalyst was nil, while approximately 68% TOC reduction was achieved during wet oxidation over a manganese-cerium (7:3 mol/mol) catalyst at 160 degrees C and an oxygen partial pressure of 1.0 MPa. Moreover, the 5-day biochemical oxygen demand/chemical oxygen demand ratios of all the effluent streams were determined to be greater than 0.45 as the wet catalytic processes were carried out at a liquid hourly space velocity less than 24 h (-1), indicating that they could be made more amenable to further biological treatment.

Algorithms↗

PubMed1989

Cerium-based demonstration of phosphatase activity in plastic-embedded sections: a comparison with conventional methods.

Cerium-based methods have been used for the demonstration of several phosphatases at alkaline, acid and neutral pH in low temperature acetone-fixed, plastic-embedded sections. At alkaline pH calcium is used as capturing agent and the precipitated calcium phosphate converted to cerium phosphate. At neutral and acid pH cerium is used directly as capturing agent. Cerium phosphate is subsequently visualized using the H2O2-DAB method. A comparison has been made with conventional calcium-cobalt and lead methods. It appeared that calcium-cobalt methods are more susceptible to improvement than lead methods.

5'-Nucleotidase↗

PubMed2004

Effectiveness of ethylene glycol bis (2-aminoethyl ether) tetraacetic acid (EGTA) against cerium toxicity.

Therapeutic efficacy of EGTA (ethylene glycol bis (2-aminoethyl ether) tetraacetic acid) against cerium intoxicated mice was studied. Administration of cerium showed significant decrease in haemoglobin percentage, RBC counts and blood glucose level with an increase in the activity of serum transaminases and WBC counts. Decrease in the activity of alkaline phosphatase and glycogen content was noted in liver and kidney after cerium exposure. Light and electron microscopical investigations showed that these changes were recouped considerably with the administration of EGTA suggesting its therapeutic efficacy against cerium toxicity.

Alkaline Phosphatase↗

PubMedDate not supplied

Effects of ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) derivatives on penetration of ytterbium-169 and cerium-144 into the rat offspring.

Effects of ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) derivatives on penetration of ytterbium-169 and cerium-144 into the rat offspring. Acta Physiol. Pol., 1976, 27 (2): 175-181. Penetration of radioactive ytterbium-169 and cerium-144 into fetuses was determined at the end of pregnancy and penetration into the organism of suckling rats was studied during feeding with the milk of exposed mothers when EDTA or DTPA derivatives were being administered. Injection of ytterbium-169 as a complex with EDTA or DTPA or injection of Na2Ca EDTA or Na3Ca DTPA 1h after administration of cerium-144 to mothers reduced penetration of both radionuclides into offsprings in relation to the animals receiving no complex compounds. It was observed that the action of DTPA was stronger than that of EDTA. Passage of ytterbium with milk and across the placenta was greater than the passage of cerium.

Animals↗

PubMed2003

Preparation of mesoporous carbon from commercial activated carbon with steam activation in the presence of cerium oxide.

Mesoporous carbon was prepared from the commercial activated carbon by steam activation with cerium oxide as catalyst. Steam activation with a catalyst loading of 0.5-2.0 wt% at 680-870 degrees C was examined. The surface area and pore size were evaluated by nitrogen adsorption at 77 K, and the structure of cerium oxide was characterized by XRD, XPS, and TEM. The results showed that the catalyst promoted the development of a mesopore at lower temperature (680-740 degrees C), and the mesopore was concentrated around 4-10 nm. The noncatalytic activation was advantageous in mesopore development and the catalyst would restrict the formation of mesopores at high temperature (800-870 degrees C). Higher loading of cerium oxide and higher activation temperature caused the aggregation of cerium oxide and then resulted in scattered pore size distribution.

Journal Article↗

PubMed2005

Highly efficient photoinitiation in the cerium(III)-catalyzed aqueous autoxidation of sulfur(IV). An example of comprehensive evaluation of photoinduced chain reactions.

The photoinitiated and cerium(III)-catalyzed aqueous reaction between sulfite ion and oxygen has been studied in a diode-array spectrophotometer using the same light beam for excitation and detection. Cerium(III) is identified as the photoactive absorbing species, and the production of cerium(IV) initiates a radical chain reaction. To interpret all the experimental findings, a simple scheme is proposed, in which the additional chain carriers are sulfite ion radical (SO3(-.)), sulfate ion radical (SO4(-.), and peroxomonosulfate ion radical (SO5(-.). The overall rate of oxidation is proportional to the square root of the light intensity per unit volume, which is readily interpreted by the second-order termination reaction of the proposed scheme. It is also shown that the reaction proceeds for an extended period of time in the dark following illumination, and a quantitative analysis is presented for this phase as well. The postulated model predicts that cerium(III) should have a cocatalytic or synergistic effect on the autoxidation of sulfite ion in the presence of other catalysts. This prediction was confirmed in the iron(III)-sulfite ion-oxygen system. The experimental method and the mathematical treatment used might be applicable to a wide range of photoinduced chain reactions.

Journal Article↗

PubMed2006

[Spectroscopic characterization of structure of cerium incorporated MCM-48 mesoporous molecular sieve].

Cerium incorporated MCM-48 molecular sieves have been hydrothermally synthesized using a mixed template and pH adjusting route. The samples were characterized by various physicochemical methods, including X-ray diffraction, diffuse reflectance UV-Vis spectroscopy, FTIR spectroscopy, XRF spectroscopy, and nitrogen adsorption. These results reveal that cerium is incorporated in MCM-48 and it is in the form of well-dispersed tetra-coodinated cerium ion. The proper concentration of cerium and adjusting pH can keep Ce-MCM-48 with higher specific surface area , larger unit-cell parameter, narrower pore-size distribution, and thicker pore wall than those of MCM-48. These deduce higher activity, and better selectivity, thermal stability and hydrothermal stability than those of MCM-48. The concentration of Ce incorporated in MCM-48 affects the vibration of the framewoke Si of molecular sieves.

English Abstract↗

PubMed2000

Cytotoxic activity of cerium complexes with coumarin derivatives. Molecular modeling of the ligands.

Cerium complexes of Umbellipherone, Mendiaxon, Warfarin, Coumachlor, and Niffcoumar have been synthesized by reaction of the ligands with cerium nitrate in a stoichiometric ratio of 1:2. The formation of the complexes has been proved on the basis of elemental analysis, conductivities, IR spectroscopy, and 1H-NMR spectroscopy. The molecules of the ligands were optimized by means of the semiempirical quantum mechanical method PM3 to the energetically most stable conformers. All the ligands were characterized by molecular and submolecular electronic indices and the putative donor centers are proposed. It is concluded that the lactone- and the keto-carbonyl groups of Warfarin, Coumachlor, and Niffcoumar are bonded to the metal ion as bidentate ligands. The other two coumarins are bonded as monodentate ligands. Conductivity measurements show the non-electrolytic nature of the complexes. Cytotoxic screening by MTT assay was carried out. The cerium complexes were found to be more active than the inorganic salts.

4-Hydroxycoumarins↗

PubMed1986

Phosphatase cytochemistry with cerium as trapping agent. Verification of acid phosphatase and glucose-6-phosphatase reactive sites.

Lead is prevalently replaced by cerium as trapping agent in phosphatase cytochemistry to prevent non-specific precipitation. Recently, substrate specific but artefactual lead precipitates have been described in the nuclear envelope (NE) and rough endoplasmic reticulum (RER) due to a local matrix effect. In the present study a verification was carried out of the localization of acid phosphatase and glucose-6-phosphatase in the NE and RER of rat peritoneal macrophages and hepatocytes respectively with cerium. It appeared that precipitates of cerium phosphate in NE and RER of peritoneal macrophages do not represent sites of acid phosphatase activity but are due to the matrix effect. However, in rat hepatocytes these organelles demonstrate true reactive sites for glucose-6-phosphatase.

Acid Phosphatase↗

PubMed1985

Cytochemical demonstration of adenylate cyclase activity with cerium.

Cerium was applied for the ultrastructural, cytochemical localization of adenylate cyclase (EC 4.6.1.1.). The enzyme activity was stimulated with norepinephrine, prenalterol and cholera toxin in the brown fat cells of newborn rats. The final reaction product was observed in the plasmalemmas of the stimulated adipocytes. The precipitate was finely crystalline, easily visible in the electron microscope and in the X-ray microprobe analysis it yielded cerium and phosphate peaks, respectively. The use of cerium offers a new tool valid for the cytochemical localization of adenylate cyclase enzyme related to the membrane receptors.

Adenylyl Cyclases↗

PubMed1996

Reflectance enzyme histochemistry (REH): visualization of cerium-based and DAB primary reaction products of phosphatases and oxidases in cryostat sections by confocal laser scanning microscopy.

In the present study the reflectance mode of confocal laser scanning microscopy was adapted to detect and to assess semiquantitatively cerium-based primary reaction products of oxidases [Ce(IV) perhydroxide] and phosphatases [Ce(III) hydroxyphosphate converted into Ce(IV) perhydroxyphosphate] as well as of the 3,3'-diaminobenzidine (DAB)-based primary reaction product of cytochrome c oxidase in cryostat sections. Confocal laser scanning microscopy offers a unique way of making visible histochemical reaction products which are weakly absorbant but sufficiently reflective. It was easily possible to record simultaneously the reflectance signals at the wavelength of the exciting laser (preferentially 488 nm) and the autofluorescence signals ( > 580 nm in our set-up) of glutaraldehyde-fixed tissue. The results of an imbibition study of cerium-containing model precipitates indicate that the cerium, generally, should be oxidized prior to observation because the index of refraction of Ce(IV) compounds is considerably higher than that of the corresponding Ce(III) compounds. An attempt at comparative numerical assessment of reflection intensities from reflectant parts in morphologically similar sections is presented. The proposed technique may open new possibilities in enzyme- and immunohistochemistry.

3,3'-Diaminobenzidine↗

PubMed1997

Cerium levels are elevated in the serum of patients with endomyocardial fibrosis (EMF).

The geochemical hypothesis on endomyocardial fibrosis (EMF) links causation of the disease to increased levels of cerium in the heart. Since cardiac tissues are not easily accessible from patients, we explored whether cerium can be detected in the serum using neutron activation analysis (NAA). Cerium levels in serum of EMF patients were significantly elevated (p < 0.05) compared to controls.

Adolescent↗

PubMed1985

Bacteriological effect of cerium-flamazine cream in major burns.

A controlled trial of the use of either 0.05 per cent chlorhexidine for bathing burn wounds or the topical application of a cream containing cerium nitrate and silver sulphadiazine showed that the cerium-flamazine cream significantly reduced the degree of Pseudomonas aeruginosa contamination of the burn wounds of patients with burns covering more than 15 per cent of the body surface area. The adherent eschar produced by treatment with cerium-flamazine provided a satisfactory wound cover until tangential excision could be carried out.

Administration, Topical↗

PubMed2005

Application of cerium nitrate-silver sulphadiazine allows for postponement of excision and grafting.

Early excision and grafting cannot always be performed due to patient's medical status, and the lack of adequate donor sites. The use of cerium nitrate-silver sulphadiazine cream, which causes the formation of a leather-like eschar with excellent resistance to infection, is an alternative method. In order to postpone operations by using cerium nitrate-silver sulphadiazine, we compared the differences in contamination of the grafted areas between early and delayed excision. Eighteen patients underwent excision and grafting within 5 days post burn and nineteen patients were surgically treated after 5 days. Twelve months later the grafted areas were evaluated. Contamination of the grafted area occurred in 17 patients. No differences in contamination occurred between the early and delayed excision group, 8 versus 9. Also no differences in type of organism cultured and follow-up results were found between the early and delayed excision group. Cerium nitrate-silver sulphadiazine allows surgical treatment to be delayed without an increase of contamination of the grafted area and does not adversely affect the long-term outcome.

Adolescent↗

PubMedDate not supplied

Simple fluorimetric method for determination of certain antiviral drugs via their oxidation with cerium (IV).

A simple and sensitive fluorimetric method for determination of antiviral drugs: ribavirin, acyclovir, and amantadine hydrochloride has been developed. The method was based on the oxidation of these drugs by cerium(IV) in presence of perchloric acid and subsequent monitoring the fluorescence of the induced cerium(III) at lambdaexcitation 255 and lambdaemission 355 nm. Different variables affecting the reaction conditions such as the concentrations of cerium(IV), type and concentration of acid medium, reaction time, temperature, and the diluting solvents were carefully studied and optimized. Under the optimum conditions, linear relationships with good correlation coefficients (0.9978-0.9996) were found between the relative fluorescence intensity and the concentrations of the investigated drugs in the range of 50-1400 ng ml-1. The assay limits of detection and quantitation were 20-49, and 62-160 ng ml-1, respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 1.58%. No interference could be observed from the excipients commonly present in dosage forms. The proposed method was successfully applied to the analysis of the investigated drugs in pure and pharmaceutical dosage forms with good accuracy and precision; the recovery percentages ranged from 99.2 to 101.2+/-0.48-1.30%. The results obtained by the proposed fluorimetric method were comparable with those obtained by the official method stated in the United States Pharmacopoeia.

Acyclovir↗

PubMed2006

The surfactant sensitized analytical reaction of cerium(IV) with some triphenylformazan derivatives.

Cationic surfactant, cetylpyridinium bromide (CPB), sensitizes the colour reaction of cerium(IV) with 1,3-o-hydroxyphenyl-5-phenylformazan(I), 1-m-hydroxyphenyl-3-o-hydroxyphenyl-5-phenylformazan(II) and 1-m-carboxyphenyl-3-o-hydroxyphenyl-5-phenylformazan(III). The formation of a soluble ternary complex of stoichiometric ratio 1:1:1 (Ce(IV)-R-CPB) is responsible for the observed enhancement in the molar absorptivity and Sandell sensitivity of the formed complex, when a surfactant is present. The ternary complex exhibits absorption maxima at 596, 571 and 607 nm (epsilon=6.05 x 10(4), 6.28 x 10(4) and 8.06 x 10(4)L mol(-1)cm(-1)) using triphenylformazan derivatives I, II and III, respectively. Beer's law is obeyed between 0.15 and 2.5 microg ml(-1), whereas, optimum concentration range applying Ringbom method is in the range 0.30-2.25 microg ml(-1). Conditional formation constants in the presence and absence of CPB for Ce(IV) complexes have been calculated. The proposed method has been successfully applied to the analysis of magnesium-base cerium alloys and synthetic mixtures corresponding to various cerium alloys.

Alloys↗

PubMed1993

Light microscopic visualization of monoamine oxidase using a cerium method.

H2O2-generating monoamine oxidase can be visualized in the light microscope with tetrazolium, metal salt (ferricyanide) and coupled peroxidatic oxidation methods. Due to methodological draw-backs these procedures do no allow satisfactory results. In search for an alternative method a light microscopic cerium procedure was designed in which the primary reaction product, cerium perhydroxide, serves for the generation of amplified and intensified diaminobenzidine brown. With this cerium-diaminobenzidine-H2O2-Co method monoamine oxidase was visualized more easily and reliably and with higher sensitivity and more precise localization than with the other techniques. At present this method is considered to be the procedure of choice and was used to re-investigate and investigate the distribution of monoamine oxidase in rats, mice, gerbils, guinea-pigs, marmosets, monkeys and man. In these species many cells and tissues showed monoamine oxidase activity where the enzyme has not yet been found before and the structures with already known monoamine oxidase activity showed an improved localization.

Animals↗

PubMed1986

Cytochemical localization of adenylate cyclase activity in heart tissue with cerium.

Adenylate cyclase (AC) activity showed a doses depending inactivation of the basal activity and of the sodium fluoride stimulation by cerium in homogenates of unfixed and fixed guinea pig hearts. The isoproterenol and guanine nucleotide stimulation was not more than two times of the basal activity in glutaraldehyde-prefixed heart homogenates in the presence of 2 mmol/l CeCl3. The inactivation of the AC (activity) by cerium was less than in the presence of lead. Test tube experiments showed no differences in the precipitation of imidodiphosphate in comparison with inorganic phosphate. The substrate AMP-PNP was not spontaneously hydrolysed by 2 mmol/l CeCl3. Ultrastructural analysis of cytochemical incubation of glutaraldehyde-fixed slices and small pieces of guinea pig heart tissue showed fine-amorphous precipitations of reaction products localized along the plasma membrane of the sarcolemma, the nexuses of the intercalated discs and the T-tubule membranes. No precipitates were found neither on the junctional nor on other SR membranes. Nonspecific coarse and clumped precipitates have been detected in the intercellular space on components of the basal membranes. It was not able to demonstrate cytochemically stimulation of AC by hormones or by sodium fluoride. The localization of the basal AC activity in heart tissue seems to be better with cerium as capture agent than with lead. However, differences in the localization of the AC activity in heart tissue were not observed.

Adenylyl Cyclases↗