Non-buffered pH Research Articles

Organic Amendment Effects on the Transformation and Fractionation of Aluminum in Acidic Sandy Soil

Addition of organic amendments can alleviate the level of aluminum (Al) phytotoxicity in acid soils by affecting the nature and quantity of Al species. This study evaluated the transformation of Al in an acidic sandy Alaquod soil amended with composts (10 and 50 g kg−1 soil of yard waste, yard + municipal waste, GreenEdge®, and synthetic humic acid) based on soil Al fractionation by single and sequential extractions. Though the organic compost amendments increased total Al in soil, they alleviated Al potential toxicity in acidic soil by increasing soil pH and converting exchangeable Al to organically bound and other noncrystalline fractions, stressing the benefits of amending composts to improve acid soil fertility. The single‐extraction method appears to be more reliable for exchangeable Al than sequential extraction because of the use of nonbuffered pH extract solution. Florida Agricultural Experiment Station – Indian River Research and Education Center Journal Series Number R‐100601.

Ozonation of Cisplatin in Aqueous Solution at pH 9

Ozonation of cisplatin [cis-diamminedichloroplatinum (II)] in non-buffered and buffered aqueous solutions at pH 9 was carried out at 303 K in a semi batch system at laboratory scale. The degradation of cisplatin and the formation of reaction products were analyzed by reverse phase high performance liquid chromatography. In the first two minutes of reaction practically all the initial cisplatin was depleted and only one major peak was observed in chromatograms under both experimental conditions. The structure of this main product was proposed after analysis by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The mutagenicity of reaction mixture at non-buffered pH 9 was evaluated by performing Ames test. Non-mutagenic effect was observed. The second-order reaction rate constant of cisplatin with hydroxyl radical at pH 9 and 303 K was determined.

Stability and ocular tolerance of cyclophosphamide-loaded nanospheres

The physical and chemical stabilities of several formulations of cyclophosphamide-loaded polybutylcyanoacrylate (PBCA) nanospheres developed for an ophthalmic application as an immunosuppressive agent were studied over 6 months of storage at 4, 25 and 40°C in different experimental conditions. The physical stability of nanospheres was followed by the study of morphological (visual appearance) and morphometrical properties (mean particle size and polydispersity). The pH and tonicity of the suspensions and the association efficiency of the drug to polymeric system were also analysed to evaluate their chemical stability. The behaviour of colloidal suspensions with storage conditions was also followed by differential scanning calorimetry. The degradation of PBCA was affected by temperature and pH. The average particle size of all nanospheres remained practically unchanged throughout the study, with the polydispersity index being less than 0.1, corresponding to a monodisperse system. At 40°C, a loss of 25.9% of the initial association efficiency, especially in non-buffered pH 7.2 medium, was observed. The type of polymer degradation (surface erosion) was also determined by photon correlation spectroscopy. The results obtained from in vivo study of ocular tolerance indicate a good ocular tolerance for drug loaded to nanospheres.

Solubilization and Hydrolysis of Ovotransferrin Solubilization of α-chymotrypsin. Enthalpy changes for three processes

At 298.15 K, the solubilization of hen ovotransferrin at buffered pH 7.8 (0.08 M Tris⋅HCl buffer, containing 0.1 M CaCl2) and the solubilization of α-chymotrypsin (from bovine pancreas) at non-buffered pH 3.0 (0.001 M HCl) both resulted in large exothermic reactions, being the apparent ΔHs –2485 in the first case and –780.1 kJ mol–1 in the second case, respectively. By contrast, the complete hydrolysis of ovotransferrin (pH 7.8) achieved by using a-chymotrypsin (pH 3.0) gave an endothermic reaction with ΔH=+31.84 kJ mol–1.

Stability of poly (ε caprolacton) nanospheres in sterile aqueous media

Polyester nanoparticles have shown promising results in the ophthalmic area for optimization of the bioavailability of drugs. However, polyesters can undergo hydrolysis during storage in aqueous media and their degradation can be enhanced by micro-organisms. Poly (ε caprolacton) (PEC) nanospheres were formulated for an ophthalmic application, i.e. sterile, isotonic and containing a preservative. Their physical and chemical stabilities were studied during a 6-month storage at 25 and 40°C. The influence of temperature, surfactant, viscosifiant addition, and buffered or non-buffered pH was evaluated. The physical stability of nanospheres was followed by the study of visual appearance and mean particle size. The pH and tonicity of the suspensions, and the molecular weight and crystallinity of PEC were additionally analyzed to evaluate their chemical stability. The influence of surfactants was observed only on the nanosphere physical stability. Better results were obtained with Pluronic F127. The degradation of PEC was especially affected by pH and temperature. At 25°C and pH 7, the variation of polymer molecular weight was negligible. At 40°C, the hydrolysis rate increased with a loss of 50% of the initial molecular weight after 6 months in pH 7 buffer, and 60% in non-buffered pH 7 medium. Finally, the mean particle size of all nanospheres remained unchanged throughout this study.