Effect of pH, phosphate buffer concentration and the ionic strength on the stability of cefotetan disodium

The stability of cefotetan disodium between the pH range 2-8 has been studied using a stability-indicating HPLC assay method. The optimum pH range of stability appears to be 3.6-6.4. At pH 2 or 8, the decomposition was approximately 2 times faster than between pH 3.6-6.4. The HPLC method used is accurate and precise with percent relative standard deviation of 1.0 based on 5 readings. The decomposition of cefotetan followed first-order law. The K_h and K_oh values were estimated to be 3.8 and 4.4 × 10⁴ d^-1.     

Synthesis and Characterization of Carboxylated Luteolin (CL)-Functionalized SPION

In this study, a stable carboxylated luteolin (CL)-functionalized superparamagnetic iron oxide nanoparticle (SPION) as a potential drug carrier for in vitro analysis of L929 (mouse fibroblast), U87 (glioblastoma (brain cancer)), MCF-7 (breast cancer), HeLa (cervix cancer), and A549 (human lung cancer) cell lines has been synthesized. Thermal decomposition and Stöber methods were used to prepare 3-aminopropyl triethoxysilane-capped SPIONs respectively. Carboxylated polyethylene glycol (PEG-COOH), folic acid (FA), and CL were conjugated on the surface via a carboxylic/amine group using the nanoprecipitation method respectively. Internalization of CL-functionalized SPION and the release of luteolin from it has been studied using Prussian blue staining and spectrophotometry respectively. The cytotoxicity of CL-functionalized SPION on cell lines was tested by MTT assay. Internalization of product by HeLa, MCF-7, and U87 was higher than A549 and L929 cells. It was observed that luteolin release increased in an acidic environment (pH 5.4). A newly synthesized SPION-FA-PEG in all concentrations (except 500 μg/mL) did not show notable toxicity against L929, U87, MCF-7, HeLa, and A549. However, the product in all used concentrations decreased cell viability at the 24th and 48th hours. This study confirmed that the product has a potential to be used as an anti-cancer CL-functionalized SPION for targeted drug delivery.     

Stability of Omeprazole Solutions at Various ph Values as Determined by High-Performance Liquid Chromatography

A stability-indicating HPLC assay method for the quantitation of omeprazole has been developed. The developed method was used to study the effect of pH on the stability of omeprazole and to quantify the drug in capsules. The excipients present in the capsules did not interfere with the assay procedure. The pH-rate profile curve indicated that the maximum stability was at pH 11. Below pH 7.8, the decomposition was very fast. The decomposition constants have a direct relationship with the H+ concentrations of the solutions.     

Use of adsorption process to remove organic mercury thimerosal from industrial process wastewater

Carbon adsorption process is tested for removal of high concentration of organic mercury (thimerosal) from industrial process wastewater, in batch and continuously flow through column systems. The organic mercury concentration in the process wastewater is about 1123 mg/L due to the thimerosal compound. Four commercially available adsorbents are tested for mercury removal and they are: Calgon F-400 granular activated carbon (GAC), CB II GAC, Mersorb GAC and an ion-exchange resin Amberlite GT73. The adsorption capacity of each adsorbent is described by the Freundlich isotherm model at pH 3.0, 9.5 and 11.0 in batch isotherm experiments. Acidic pH was favorable for thimerosal adsorption onto the GACs. Columns-in-series experiments are conducted with 30-180 min empty bed contact times (EBCTs). Mercury breakthrough of 30 mg/L occurred after about 47 h (96 Bed Volume Fed (BVF)) of operation, and 97 h (197 BVF) with 120 min EBCT and 180 min EBCT, respectively. Most of the mercury removal is attributed to the 1st adsorbent column. Increase in contact time by additional adsorbent columns did not lower the effluent mercury concentration below 30 mg/L. However, at a lower influent wastewater pH 3, the mercury effluent concentration decreased to less than 7 mg/L for up to 90 h of column operation (183 BVF).     

In-Vitro Evaluation of Antacid Suspension

Abstract

Three conceptually different titration procedures are used to evaluate the performance of several antacid suspension products: RIOPAN, RIOPAN PLUS, MAALOX, MAALOX PLUS, AND MYLANTA. When the static acid neutralization capacity test is performed, both RIOPAN and RIOPAN PLUS possess more acid neutralizing capacity, on an equal weight basis, than MAALOX, MAALOX PLUS or MYLANTA. The results of a pH-stat titration test show the RIOPAN products react 10 times faster with acid than other produced based on time to half-neutralization. The dynamic acid neutralizing capacity test (modified Beekman procedure) shows onset of action at pH 3 for the RIOPAN product to be 20 times faster than for MAALOX PLUS and 56 times faster than for MYIANTA. Duration of acid neutralization at pH above 3 for the RIOPAN products is two times longer than for MAALOX or MAALOX PLUS and 1.6 times longer than for MYIANTA.     

Effect of pH,phosphate buffer concentration and the ionic strength on the stability of cefotetan disodium

Abstract

The stability of cefotetan disodium between the pH range 2-8 has been studied using a stability-indicating HPLC assay method. The optimum pH range of stability appears to be 3.6-6.4. At pH 2 or 8, the decomposition was approximately 2 times faster than between pH 3.6-6.4. The HPLC method used is accurate and precise with percent relative standard deviation of 1.0 based on 5 readings. The decomposition of cefotetan followed first-order law. The K_h and K_oh values were estimated to be 3.8 and 4.4 × 10⁴ d^-1.     

PBAMO的热分解反应机理

采用无模型法对聚3,3-双叠氮甲基环氧丁烷(PBAMO)的热分解反应动力学进行了计算,并用热重-红外-质谱(TG-IR-MS)联用技术研究了其热分解反应产物。PBAMO表现出了独特的热分解过程,TG曲线中在210℃~270℃叠氮基团的分解失重之后没有第二个明显的失重台阶;PBAMO第一阶段的热分解活化能为150 kJ/mol,当分解率大于0.4时,活化能降为负值。TG-IR-MS结果表明,在叠氮基团分解时释放的热量加速了剩余氮原子的氧化还原过程,主要产物形式为NO,主链中的氧原子被消耗掉,从而导致了碳链骨架的大量残留。     

Photolytic (UVC) and photocatalyic (UVC/TiO2) decomposition of pyridines

The degradation of 2-chloropyridine (2-CPY) and its degradation primary product 2-hydroxypyridine (2-HPY) was studied by means of ultraviolet (UV) irradiation at 254nm. Photolytic and photocatalytic experiments were conducted on 2-CPY and 2-HPY aqueous solutions in a batch reactor with internal recycle in laminar and turbulent conditions at 50 degrees C in a closed but not airtight system with and without additional aeration, at solution ambient pH and at controlled pH conditions, with use and in the absence of radical scavenger. The solution volume was 0.4L and initial substrate concentrations were approximately 2.6mmol/L (0.25-0.3g/L depending on the substrate). Where applicable 1g/L TiO(2) (P-25) was used, suspended in the liquid in a form of turbulent slurry or using a glass tube around the UV-lamp on which a fixed TiO(2) catalytic layer had been deposited. At the aforementioned conditions 2-CPY readily degrades photolytically, the catalytic path having very little influence. In all cases 2-CPY produces 2-HPY which further degrades to other products. Aeration, pH and the presence of catalyst and/or radical scavengers do not affect the rate of decomposition of 2-CPY, but have a strong influence on the further decomposition of the produced 2-HPY. 2-HPY decomposition proceeds both catalytically and photolytically following oxygen dependent and oxygen independent pathways.     

Stability of Omeprazole Solutions at Various ph Values as Determined by High-Performance Liquid Chromatography

Abstract

A stability-indicating HPLC assay method for the quantitation of omeprazole has been developed. The developed method was used to study the effect of pH on the stability of omeprazole and to quantify the drug in capsules. The excipients present in the capsules did not interfere with the assay procedure. The pH-rate profile curve indicated that the maximum stability was at pH 11. Below pH 7.8, the decomposition was very fast. The decomposition constants have a direct relationship with the H+ concentrations of the solutions.     

High-performance liquid chromatographic determination of flavoxate hydrochloride and its hydrolysis product

Liquid chromatographic method was presented for the determination of flavoxate hydrochloride (FX) and its hydrolysis product. The method was based on high-performance liquid chromatographic (HPLC) separation of FX from its hydrolysis product on CN column using a mobile phase consisting of acetonitrile-12 mM ammonium acetate (45:55, vol/vol, pH 4.0) with UV detection at 220 nm and flow rate of 1.5 mL min(-1). The proposed HPLC method for the determination of FX was utilized to investigate the kinetics of acidic hydrolytic process at different temperatures and to calculate its activation energy. In addition, the proposed HPLC method was used for pH-rate profile study of hydrolysis of FX in Britton-Robinson buffer solutions. The 3-methylflavone-8-carboxylic acid ethyl ester, as impurity of flavoxate hydrochloride, can be separated by the proposed HPLC method.     

High-Performance Liquid Chromatographic Determination of Flavoxate Hydrochloride and its Hydrolysis Product

Liquid chromatographic method was presented for the determination of flavoxate hydrochloride (FX) and its hydrolysis product. The method was based on high-performance liquid chromatographic (HPLC) separation of FX from its hydrolysis product on CN column using a mobile phase consisting of acetonitrile-12 mM ammonium acetate (45:55, vol/vol, pH 4.0) with UV detection at 220 nm and flow rate of 1.5 mL min^?1. The proposed HPLC method for the determination of FX was utilized to investigate the kinetics of acidic hydrolytic process at different temperatures and to calculate its activation energy. In addition, the proposed HPLC method was used for pH-rate profile study of hydrolysis of FX in Britton–Robinson buffer solutions. The 3-methylflavone-8-carboxylic acid ethyl ester, as impurity of flavoxate hydrochloride, can be separated by the proposed HPLC method.     

Stability of Vancomycin Hydrochloride Solutions at Various PH Values as Determined by High-Performance Liquid Chromatography

A stability-indicating HPLC assay method for the quantitation of vancomycin HCl has been developed. The developed method was used to study the effect of pH, phosphate buffer concentration and ionic strength on the stability of vancomycin HCl. The pH-rate profile curve showed 3 regions, acid-catalyzed, general base-catalyzed and the pH-independent region. The region of maximum stability was between pH 3.0 to about 5.7. On increasing the buffer concentration, phosphate ions hastened the decomposition of vancomycin HCl, the effect being more pronounced at pH 6.85 than at pH 4.43. In the pH region of 1-3, the decomposition was catalyzed by H⁺ and between pH 3-7 by HPO₄^2-, H₂PO₄^- and OH^-. An increase in the ionic strength decreased the rate of decomposition.     

Photocatalytic reduction of nitrate in wastewater using ZnO nanopowder synthesized by solution combustion method

ZnO nanopowder was synthesized by a unique method which is called solution combustion method (SCM). This nanopowder was used for a photocatalyst to decompose nitrate that is a toxic pollutant in wastewater. It has been known that TiO2, the most popular photocatalyst, does not decompose the nitrate. In this paper, however, the SCM ZnO nanopowder decomposed about 13% of nitrate. Furthermore, adding methanol as a hole scavenger, the decomposition rate was enhanced by about 5 times. On the other hand, it has been reported that the photocatalytic reduction reaction of nitrate produces ammonia as a final product. The present results, however, suggest that the final product is non-toxic nitrogen gas rather than the toxic ammonia. These results would be very valuable for drinking water purification.     

Kinetic and Biopharmaceutical Study of an Antiviral Agent in Aqueous Vehicle and Human Gastric Fluid

WIN 54954 is an investigative antiviral compound that is insoluble in water and very unstable in acidic pH. Both factors can potentially limit in vivo absorption and availability. Degradation involves hydrolytic opening of the oxazoline ring, which results in loss of antiviral activities. The degradation product in acid is mostly an aminoethylester, WIN 55696, which further decomposes in basic medium into the hydroxyethylamide, WIN 55795. WIN 54954 decomposition in buffer solution is pH dependent and follows first-order kinetics. The stability half-life of WIN 54954 in 0.1 N hydrochloric acid is less than I hr at body temperature. A series of in vitro experiments were conducted to evaluate the stability of the drug in human gastric fluid (HGF) from volunteers. These studies demonstrate that the presence of digestive enzymes of HGF did not alter the nature of oxazoline ring opening substantially. The decomposition products identified were similar to products identified in in-vitro buffered solutions. The rate of decomposition is faster in genuine human gastric fluid than in 0.1 N HCl. Decomposition is also pH dependent and does not vary among individuals.     

Electrochemical etching of copper indium diselenide surface

CuInSe₂ thin films were grown onto ITO surface by electrodeposition and annealed in the hydrogen atmosphere at 400 °C. The influence of traditional chemical etching (KCN etchant) and electrochemical etching at various potentials and values of solution pH (0.8-13) on the surface composition and morphology was studied using the EDX and SEM methods. The mechanism of CuInSe₂ decomposition at various pH values was examined by cycling voltammetry. The influence of chemical and electrochemical etchings on electrical and optical characteristics of thin films was analyzed.     

Adsorptive removal of Cu(II) from aqueous solutions using collagen-tannin resin

The collagen-tannin resin (CTR), as a novel adsorbent, was prepared via a reaction of collagen with black wattle tannin and aldehyde, and its adsorption properties to Cu(II) were systematically investigated, including pH effect, adsorption equilibrium, adsorption kinetics, and column adsorption. The adsorption capacity of Cu(II) on CTR was pH-dependent, and it increased with the increase of solution pH. The adsorption isotherms were well described by Langmuir isotherm model with correlating constant (R(2)) higher than 0.99. The adsorption capacity determined at 303 K was high up to 0.26 mmol/g, which was close to the value (0.266 mmol/g) estimated from Langmuir equation. The adsorption capacity was increased with the increase of temperature, and thermodynamic calculations suggested that the adsorption of Cu(II) on CTR is an endothermic process. The adsorption kinetics were well fitted by the pseudo-second-order rate model. Further column studies suggested that CTR was effective for the removal of Cu(II) from solutions, and more than 99% of Cu(II) was desorbed from column using 0.1 mol/L HNO(3) solution. The CTR column can be reused to adsorb Cu(II) without any loss of adsorption capacity.     

Preparation and characterization of zero valent iron powders via transfer type reductor using iron oxide from the acid regeneration process

In this study, zero valent iron (ZVI) powders were generated by reducing iron oxide powders obtained from a pickling line in a transfer type reductor. The physical and chemical characteristic of the produced ZVI powders were analyzed by using instruments. Reaction activities of ZVI powders for decomposition of a methylene blue were evaluated. The mean size of ZVI powders increased and the specific surface area decreased with increasing reduction temperature due to sintering. The methylene blue decomposition rate increased with dose of ZVI powders. The ZVI powders generated by reducing iron oxide showed higher decomposition efficiencies than the commercial ZVI powders at all pH values tested in this study. Both non-commercial ZVIs showed a higher decomposition rate at a lower pH.     

An improved high-performance liquid chromatography assay for spironolactone analysis

This study prepared an extemporaneously formulated liquid suspension dosage form (5 mg/ml) from commercially available 25 mg tablets. Stability-indicating HPLC assay procedures were established and utilized to analyze the concentration of the drug. The method proved to be a simple model since it does not contain a buffer system. The mobile phase used was the same as that suggested by the manufacturer for the storage of the column. Therefore, the solvent system saves analytical processing time, since it does not require a change in the mobile phase before or after the analysis. The analytical method has been shown to be stability-indicating. The results have shown that there is no interference from any of the degradation products obtained from stressing spironolactone by heat and extremes in pH or with the internal standard, hydrocortisone 21-acetate.