Degradation Rate Of Acid Research Articles

Stability-indicating derivative spectrophotometric determination of frusemide

The development of a first- and second-derivative spectrophotometric determination of frusemide in pharmaceutical formulations in the presence of its acid-hydrolysis product ‘saluamine’, is described. The produce involves measurements of first-derivative amplitudes at 254 and 262 nm (1D254and1D262) and second-derivative amplitudes at 265 and 272 nm (2D265 and2D272) for the assay of frusemide and saluamine, respectively. Kinetic investigation of the acid degradation rate of frusemide revealed that the proposed method is stability indicating. Tablets and injections have been assayed and the results indicated that the proposed derivative spectrophotometric method is as accurate and precise as the official method.

Identification of Products from Oxidation of Uric Acid Induced by Hydroxyl Radicals

The aim of the present study was to separate and characterise products formed by oxidation of uric acid by hydroxyl radicals with a view to probing for these products in vivo in clinical contexts. Aerated solutions of 200 microM uric acid, or its oxidation products, allantoin or parabanic acid, were exposed to gamma radiolysis, (52.0 Gy/min), as a source of HO. radicals, at pH 3.4 and 7.4. Aliquots were taken every 5 minutes for 20 minutes and oxidation products were separated by HPLC and analysed with a diode array detector. Identities of oxidation products were confirmed on the basis of similarity of retention times and absorbance spectra and peak purity parameters of known standards. Hydroperoxides were measured by tri-iodide formation in the 20 minute sample. Exposure of uric acid to such HO.fluxes produced a net loss of the parent compound with formation of a complex mixture of products with allantoin and parabanic acid being the predominant products at pH 3.4. The rate of uric acid degradation at physiological pH was slower and the distribution of oxidation products was different. A small but significant amount of uric acid hydroperoxide was detected at both pHs. A mechanism for uric acid oxidation under these conditions is presented.

Influence of chemisorption on the photodecomposition of salicylic acid and related compounds using suspended titania ceramic membranes

The adsorption and photodecomposition on semiconducting membranes of molecules with different functional groups were studied. Ceramic membranes, prepared by a sol-gel technique, were employed because this technique provides some control over surface area, porosity, and crystal form of these materials, properties which affect their photochemical behavior. Salicylic acid was chosen as a prototype molecule. 3-Chlorosalicylic acid, benzoic acid, phenol, and 4-chlorophenol were also investigated. The adsorption densities of salicylic and 3-chlorosalicylic acids decreased with both increasing solution pH and membrane firing temperature, in correlation with the number of positive adsorption sites on TiO2 surface. No adsorption for benzoic acid, phenol, and 4-chlorophenol was observed. Photodecomposition rates were found to depend on the adsorption characteristics of the organic compound; for salicylic acid the degradation rate diminished with increasing pH. Benzoic acid, whose degradation products adsorb on the oxide surface, showed a similar trend. No dependence on pH was detected for phenols. Methanol was found to affect the degradation rate of salicylic acid only under conditions of high pH. It is proposed that, for chemisorbing organics, the initial step of the photodecomposition process is governed by two different mechanisms that depend on the adsorption behavior of the organic compound at a particular pH. For adsorbed salicylate, an orbital configuration of the chelate ring is proposed to interpret direct electron transfer from the organic molecule to the semiconductor.

Photochemical degradation rates of tetraphenylborate and diphenylboric acid sensitized by dissolved organic matter in stream water

The photochemical degradation of tetraphenylborate (TPB) and diphenylboric acid (DPBA) was studied in stream water and humic acid solutions. The rates of indirect photolysis of TPB and DPBA were similar and directly proportional to the concentration of stream water dissolved organic matter (DOM) and humic acid for values < 10 mg/L. Direct photolysis of both organoborates was nondetectable during a 2-h irradiation period. Indirect photolysis rates varied only slightly from pH 6.0 to 9.0, but increased markedly below pH 6.0. Removal of dissolved oxygen increased reaction rates by a factor of two, indicating that the reaction mechanism does not involve singlet oxygen oxygenation.

Bioenergetic Conditions of Butyrate Metabolism by a Syntrophic, Anaerobic Bacterium in Coculture with Hydrogen-Oxidizing Methanogenic and Sulfidogenic Bacteria

The butyrate-oxidizing, proton-reducing, obligately anaerobic bacterium NSF-2 was grown in batch cocultures with either the hydrogen-oxidizing bacterium Methanospirillum hungatei PM-1 or Desulfovibrio sp. strain PS-1. Metabolism of butyrate occurred in two phases. The first phase exhibited exponential growth kinetics (phase a) and had a doubling time of 10 h. This value was independent of whether NSF-2 was cultured with a methanogen or a sulfate reducer and likely represents the maximum specific growth rate of NSF-2. This exponential growth phase was followed by a second phase with a nearly constant rate of degradation (phase b) which dominated the time course of butyrate degradation. The specific activity of H(2) uptake by the hydrogen-oxidizing bacterium controlled the bioenergetic conditions of metabolism in phase b. During this phase both the Gibbs free energy (DeltaG') and the butyrate degradation rate (v) were greater for NSF-2-Desulfovibrio sp. strain PS-1 (DeltaG' = -17.0 kJ/mol; v = 0.20 mM/h) than for NSF-2-M. hungatei PM-1 (DeltaG' = -3.8 kJ/mol, v = 0.12 mM/h). The DeltaG' value remained stable and characteristic of the two hydrogen oxidizers during phase b. The stable DeltaG' resulted from the close coupling of the rates of butyrate and H(2) oxidation. The addition of 2-bromoethanesulfonate to a NSF-2-methanogen coculture resulted in the total inhibition of butyrate degradation; the inhibition was relieved when Desulfovibrio sp. strain PS-1 was added as a new H(2) sink. When the specific activity of H(2) consumption was increased by adding higher densities of the Desulfovibrio sp. to 2-bromoethanesulfonate-inhibited NSF-2-methanogen cocultures, lower H(2) pool sizes and higher rates of butyrate degradation resulted. Thus, it is the kinetic parameters of H(2) consumption, not the type of H(2) consumer per se, that establishes the thermodynamic conditions which in turn control the rate of fatty acid degradation. The bioenergetic homeostasis we observed in phase b was a result of the kinetics of the coculture members and the feedback inhibition by hydrogen which prevents butyrate degradation rates from reaching their theoretical V(max).

Modeling dynamic experiments on the anaerobic degradation of molasses wastewater

The kinetics of anaerobic degradation of a molasses wastewater were measured under constant pH conditions in a laboratory scale packed bed reactor. In continuous and batch experiments the formation and degradation rates of the organic acids (butyric, propionic and acetic) have been followed. The influence of hydrogen gas on the acid degradation rates has been measured and, contrary to the literature and the thermo-dynamic calculations, no inhibition was detected, biofilm diffusional effects may be the reason. Two dynamic simulation models were tested, a heterogeneous model, which considered the biofilm diffusion-reaction phenomena and a quasihomogeneous model with the same kinetics. Except for hydrogen, the diffusion effects were found to be negligible. Otherwise both models gave essentially the same results and the time profiles of acids, hydrogen, carbon dioxide and methane agreed relatively well with dynamic startup experiments. Batch experiments showed the acid concentrations to be highly sensitive to the initial molasses concentration. This aspect was not included in the model but is being investigated further.

The Autodegradation of Deoxyribonucleic Acid (DNA) in Human Rib Bone and Its Relationship to the Time Interval Since Death

This research explored the feasibility of using the degradation rate of deoxyribonucleic acid (DNA) in human rib bone to determine the time interval since death. Postmortem human rib samples were surface sterilized and incubated under sterile conditions in either high or low humidity conditions at room temperature for a period of weeks. At selected times, portions of the bone were cut away, and the DNA from these samples was extracted and subjected to strand separating gel electrophoresis. The DNAs in the gels were transferred to a nylon membrane, preserving their relative positions as in the gel, and probed with radioactive total genomic human DNA. Autoradiograms produced were scanned and digitized. When the samples were incubated under identical conditions, the degradation rate of DNA in samples from different individuals appeared very similar. The DNA degradation rate may vary with temperature and humidity more than it varies between individuals.

Oxidative degradation of organic acid conjugated with sulfite oxidation in flue gas desulfurization: products, kinetics, and mechanism

Organic acid degradation conjugated with sulfite oxidation has been studied under flue gas desulfurization (FGD) conditions. The oxidative degradation constant k/sub 12/ is defined as the ratio of organic acid degradation rate and sulfite oxidation rate times the ratio of the concentration of dissolved S(IV) and organic acid. It is not significantly affected by pH or dissolved oxygen in the absence of manganese or iron. However, k/sub 12/ is increased by certain transition metals such as Fe, Co, and Ni and is decreased by Mn and halides. Lower dissolved S(IV) magnifies these effects. A free radical mechanism was proposed to describe the kinetics. Hydroxy and sulfonated carboxylic acids degrade approximately 3 times slower than saturated dicarboxylic acids, while maleic acid, an unsaturated dicarboxylic acid, degraded an order of magnitude factor. A wide spectrum of degradation products of adipic acid were found, including carbon dioxide - the major product - smaller dicarboxylic acids, monocarboxylic acids, other carbonyl compounds, and hydrocarbons. 30 references, 7 figures, 7 tables.

Potentialities of a methanogenic microbial ecosystem adapted to wine distillery wastewaters to degrade volatile fatty acids

The degradation potentiality of Volatile Fatty Acids (VFA), the major metabolic intermediates during methanization of complex organic substrates, has been evaluated. The kinetics of acetic, propionic, butyric and valeric acid degradation by the particular microbial ecosystem are of zero order in relation to the substrate, and acid degradation rate decreass with increasing length of the acid carbon chain. When microorganisms are not active, a propionate or butyrate addition results in a decrease in the acid degradation rate of 40% and 11% respectively, when the initial acid concentrations vary from 20 to 200 m M. On the other hand, if the ecosystem is already degrading propionate or butyrate, an overload of the same VFA (around 50 m M) leads to an increase in the acid degradation rate of 58% and 34%, respectively. Addition of another VFA has a significant inhibiting effect on proiionate or butyrate acetogenic activity a significant inhibiting effect on propionate or butyrate acetogenic activity (e.g. 60 m m of acetic acid decreased propionate and butyrate degradation rates by 68% and 62%,respectively). In all cases, propionate acetogenesis is much more sensitive than butyrate acetogenesis. Propionate degradation is the limiting step of the overall vinasse methanization for the ecosystem studied.

Effect of Initial Dissolved Oxygen Levels on the Degradation of Ascorbic Acid and the Browning of Lemon Juice during Storage

ABSTRACTThe effect of different initial dissolved oxygen concentrations (0.41, 1.44, and 3.74 mg/L) on rate of deteriorative quality changes [ascorbic acid degradation, browning, hydroxymethylfurfural (HMF) and furfural production) in lemon juice stored at 36°C was investigated. No significant effects on rate of ascorbic acid degradation and furfural formation could be attributed to the different oxygen levels. Degradation of ascorbic acid appeared to be predominantly anaerobic. Lag period before browning increased depended on oxygen level. Zero‐, first‐ and second‐order kinetic models were fitted to various degradative reactions occurring in lemon juice during storage. Highly significant correlations were obtained between browning index, HMF, and furfural formation, suggesting that all three would be suitable as chemical indices of storage temperature abuse in lemon juices.

Effects of sorption on biological degradation rates of (2,4-dichlorophenoxy) acetic acid in soils.

Three mathematical models were proposed to describe the effects of sorption of both bacteria and the herbicide (2,4-dichlorophenoxy)acetic acid (2,4-D) on the biological degradation rates of 2,4-D in soils. Model 1 assumed that sorbed 2,4-D is not degraded, that only bacteria in solution are capable of degrading 2,4-D in solution, and that sorbed bacteria are not capable of degrading either sorbed or solution 2,4-D. Model 2 stated that only bacteria in the solution phase degrade 2,4-D in solution and that only sorbed bacteria degrade sorbed 2,4-D. Model 3 proposed that sorbed 2,4-D is completely protected from degradation and that both sorbed and solution bacteria are capable of degrading 2,4-D in solution. These models were tested by a series of controlled laboratory experiments. Models 1 and 2 did not describe the data satisfactorily and were rejected. Model 3 described the experimental results quite well, indicating that sorbed 2,4-D was completely protected from biological degradation and that sorbed- and solution-phase bacteria degraded solution-phase 2,4-D with almost equal efficiencies.

Kinetics of degradation of sorbic acid in aqueous glycerol solutions

Degradation of sorbic acid in aqueous glycerol solutions at pH 4·0 over the a w range 0·71–1·00 and the temperature range 40°–60°C was found to follow first-order reaction kinetics and to conform to the Arrhenius equation. Activation energy values obtained were 5·8 kcal mol −1 and 7·8 kcal mol −1 for systems at 0·80 a w with and without added Co ++, respectively. The rate of sorbic acid degradation was observed to increase with decreasing a w (i.e. increasing glycerol concentration). The presence of added Co ++ decreased the rate of sorbic acid breakdown at any particular a w or temperature. Browning of sorbate solutions during storage was markedly inhibited by Co ++.

Ascorbic acid turnover in the mosue following acute ozone exposure

Swiss Webster mice were continously exposed to an atmosphere containing 1.5 ppm ozone (O 3) for 5 dyas. Control mice breathed filtered air. Immediately following the exposure period each mouse was then injected with [1- 14C] ascorbic acid. The rate of disappearance of [1- 14C] ascorbic acid and the levels of total ascorbic acid were determined in serum, lung, liver, and the remaining carcass over a 9-day period. O 3 exposure caused transient 3ecreases in the ascorbic acid levels in liver and serum, whereas lung ascorbic acid levels increased. The apparent biological half-life of ascorbate in carcasses (minus lung and liver) from O 3-exposed mice, was significantly prolonged. Significant changes were also observed in the net flux of ascorbic acid in all tissues examined. The results indicated that the change in ascorbic acid levels in a given tissue appeared to reflect changes in the rate of ascorbic acid degradation, its mobilization or tissue compartmentalization, rather than increased synthesis in response to O 3 exposure.

Effect of Trace Mineral Fortification on the Storage Stability of Ascorbic Acid in a Dehydrated Model Food System

ABSTRACTThe catalytic influence of the transition metals, iron, copper and zinc, on the storage stability of ascorbic acid in a dehydrated model food system was studied as a function of water activity (aw). No catalysis by the added metals was observed at 0.10 and 0.40 aw. This is interpreted as a lack of metal ion mobility and/or insolubility at low aw, thus hindering the participation of the metals as catalysts. At 0.65 aw, which is in the capillary region on the adsorption isotherm, a 2–4 fold increase in the rate of ascorbic acid destruction was observed in the presence of the trace minerals. The increased rate of ascorbic acid degradation at aw 0.65 is believed to be the result of greater mobility of metal ions.

Rapid degradation of cyanuric acid by Sporothrix schenckii

Summary A strain of Sporothrix schenckii was isolated which rapidly degraded cyanuric acid. The specific rate of degradation amounted to 30 mg cyanuric acid × h−1 × (g dry weight of cells)−1. During growth the strain was able to utilize cyanuric acid as its sole nitrogen source, with a concomitant release of carbon as carbon dioxide. Resting cells degraded the compound to carbon dioxide and ammonia. The action of the degrading enzymes was induced primarily by cyanuric acid, whereas ammonia and biuret resulted in a reduction of the specific rate of cyanuric acid degradation.

RATES OF ASCORBIC ACID DEGRADATION DURING THERMAL PROCESSING OF CANNED PEAS

ABSTRACTThermal degradation rates of ascorbic acid in peas during a simulated retort operation were investigated at various temperatures. Fresh peas were blanched and vacuum sealed in thermal death time cans with brine. The canned peas were processed at ll0‐132°C for different time intervals. The ascorbic acid degradation reaction was found to be first order with an activation energy of 41 kcal/mole.

Effects of Metals and Their EDTA Complexes on the Oxidative Degradation of Linoleic Acid

A simple method for measurement of linoleic acid by high pressure liquid chromatography was developed to examine the degradation of linoleic acid in the presence of metals and their EDTA complexes. The chromatographic conditions were as follows : Column, Hitachi gel 3010-CH2OH (20cm×4mm) ; mobile phase, EtOH-0.01 N HCl (9 : 1) ; flow rate, 1 ml/min ; detector, UV (at 254nm). The degradation rate of linoleic acid was examined under following conditions : A mixture of 2.9ml of 0.05M HEPES (N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid) buffer (pH 7.2), 1.0 ml of 3 mM EDTA or distlled water, and 0.1 ml of 3 mM metal solution was placed in a test tube, 0.1 ml of 0.1 M linoleic acid in EtOH was added and the mixture was kept for 24 hr at 25°. A portion of the mixture (20 μl) was injected into the liquid chromatograph to measure residual linoleic acid. It was found that Mn2+, Cu2+, Fe3+ and Fe3+-EDTA remarkably accelerated the oxidative degradation of linoleic acid, while Mn2+-EDTA suppressed the degradation.

OXYGEN EFFECT ON THE DEGRADATION OF ASCORBIC ACID IN A DEHYDRATED FOOD SYSTEM

ABSTRACTThe stability of reduced and total ascorbic acid in a low moisture dehydrated model food system was determined as a function of water activity, moisture content, oxygen and temperature. Ascorbic acid degradation rates were satisfactorily described by first‐order kinetics and were dependent on water activity and temperature. Rate constants obtained for the model system stored with a large excess of oxygen (303 cans) were compared with those reported previously for the case of limited gaseous oxygen (TDT cans). At all conditions of temperature and water activity the degradation of ascorbic acid was greater for the condition of excess oxygen (303 cans). This effect is interpreted as reflecting the consumption of oxygen dissolved in the moisture of the product and the continuous dissolution of excess molecular oxygen present in the 303 cans. The significance of this oxygen effect is further manifested by the change in activation energies for RAA and TAA destruction at 0.1 aw from 7.0 kcal/mole limited oxygen to 10.7 kcal/ mole in excess oxygen conditions. These data suggest that dissolved and gaseous oxygen are primary factors in the storage stability of ascorbic acid in dehydrated food systems.

Chloroplast Fatty Acid Transformations in Nitrogen-Deficient and Senescent Tissues

The fatty acids of plastids from several types of mineral-deficient and senescent tissues were analyzed. Incorporation of acetate into long-chain fatty acids of leaf tissue and of plastids from nitrogen-deficient and normal plants was determined. In general, the senescent and nitrogen-deficient chloroplasts contained a higher ratio of saturates to unsaturates than did plastids from younger tissues and from tissues grown on a complete nutrient.Nitrogen-deficient leaf tissue and plastids were capable of rapidly incorporating acetate into some of the fatty acids, especially palmitic and oleic acids. However, the comparative rate of acetate incorporation into linolenic acid in nitrogen-deficient chlorophyllous tissue was less than in tissue grown on a complete nutrient. With the addition of UDP-glucose to a reaction mixture containing added cofactors for noncyclic photosynthetic phosphorylation the relative incorporation of acetate into linolenate as compared to palmitate was increased in both the nitrogen-deficient and normal leaf tissue. This would indicate that nitrogen-deficient tissues have the enzymic systems for forming long-chain fatty acids but that the reduced photosynthesis limits the amount of precursors for the formation of lipids, especially galactolipids. However, nothing is known about the rate of fatty acid degradation under these conditions.

Stability of Ascorbic Acid in Commercial Liquid Multi-vitamin Preparations.

Stability of ascorbic acid contained in 21 kinds of commercial liquid multi-vitamin preparations, which had been kept for various periods at 25°, 40° and 50°, was estimated. Dates of the estimation were determined on the basis of theoretical consideration. The degree of the degradation of ascorbic acid in 67 days at 40° practically corresponded with that in one year at 25°, as theoretically expected, assuming the activation energy of ascorbic acid to be 21 kcal. It suggests a recommended condition for stability test of ascorbic acid in these preparations. The degradation rate of ascorbic acid was 10∼40% (average 27%) in one year at 25°.