PH stability

Handling and Storage. Cyanamide solution dimerizes to dicyandiamide and urea with the evolution of heat and a gradual increase in alkalinity accelerating the reaction. Storage above 30°C without pH stabilizer leads to excessive dimerization and can result in violent exothermic polymerization. Cyanamide should be stored under refrigeration and the pH tested periodically. Stabilized cyanamide can be kept at ambient temperature for a few weeks. 

Type diameter (/tm) Proteins (M,) Dextrans (M,) operating pressure (kPa) pH stability... 

Bead diameter (jum) Size exclusion pore dimension" (nm) Fractionation range Maximum operating pressure/velocity (kPa)/(cm/hr) Recommended operating linear velocity (cm/hr) pH stability (short term)... 

Type Bead size djo (/xm) Size exclusion pore dimension (nm) Exclusion limit protein (M,) Fractionation range protein (/V ,) pH stability (long term/ short term)... 

Bead size dso (/im) Size exclusion Exclusion Fractionation range pH stability... 

FIGURE 4.4 pH stability of TSK-GEL SW packings. Conditions I g of each TSK-GEL SW packing was suspended in 10 ml of buffer at indicated pH for I month. The concentration of silica dissolved in each buffer was then determined. 

Stability of the colour. The colour produced should be sufficiently stable to permit an accurate reading to be taken. This applies also to those reactions in which colours tend to reach a maximum after a time the period of maximum colour must be long enough for precise measurements to be made. In this connection the influence of other substances and of experimental conditions (temperature, pH, stability in air, etc.) must be known. 

The oil phase included a fatty acid, a fatty alcohol and hydrocarbons. The emulsion had a pH of 5.1 to 5.4, exhibited emulsion and pH stability at 37 for at least 21 days, and was shown to be an oil-in-water type by being readily dispersible in water and by its uptake of a water-soluble dye. In inhibition... 

Nielsen, I.L.F. et al., Quantification of anthocyanins in commercial black currant juices by simple high-performance liquid chromatography investigation of their pH stability and antioxidative potency, J. Agric. Food Chem., 51, 5861, 2003. 

P-carotene Yes, 40800 yellow to orange good pH stability, oil-soluble, easily oxidized 0 3... 

For suspensions primarily stabilized by a polymeric material, it is important to carefully consider the optimal pH value of the product since certain polymer properties, especially the rheological behavior, can strongly depend on the pH of the system. For example, the viscosity of hydrophilic colloids, such as xanthan gums and colloidal microcrystalline cellulose, is known to be somewhat pH- dependent. Most disperse systems are stable over a pH range of 4-10 but may flocculate under extreme pH conditions. Therefore, each dispersion should be examined for pH stability over an adequate storage period. Any... 

Molecular structure and weight Melting point Thermal profile Particle size and shape Hygroscopicity potential Ionization constant Light stability Optical activity pH solubility profile pH stability profile Polymorphism potential Solvate formation... 

The therapeutically inactive ingredients in ophthalmic solution and suspension dosage forms are necessary to perform one or more of the following functions adjust concentration and tonicity, buffer and adjust pH, stabilize the active ingredients against decomposition, increase solubility, impart viscosity, and act as solvent. The use of unnecessary ingredients is to be avoided, and the use of ingredients solely to impart a color, odor, or flavor is prohibited. 

Careful sizing of the treatment and choice of injection rates is required to prevent inadvertent overtreatment i.e., excessive treatment of oil-containing rock. The post-treatment fluid injection rate is usually significantly less than that prior to treatment. While successful applications of this technology in waterfloods and in surfactant polymer floods have been reported, temperature and pH stability limitations of the polymer and the crosslinking chemistry result in few if any applications in steam and CO2 injection wells. 

Maximum activity at T (°C), units/mg Optimum temperature (°C) Optimum pH pH stability Temperature Stability (°C) 30 min Molecular mass (kDa) Number of subunits and mass (kDa) Metal inhibitors Other inhibitors... 

It was found that decomposition is in part due to transesterification and that substitution increases stability. The effect of gamma radiation on aspirin has been described.184 The pH stability profile of aspirin according to Edwards has been made the subject of a student experiment.185... 

Modified silica with a C18 reversed-phase sorbent has historically been the most popular packing material, owing to its greater capacity compared to other bonded silicas, such as the C8 or CN types [22]. Applications of C18 sorbents include the isolation of hydrophobic species from aqueous solutions. The mechanism of interaction with such sorbents depends on van der Waals forces, and secondary interactions such as hydrogen bonding and dipole-dipole interactions. Nevertheless, the main drawbacks of such sorbents are their limited breakthrough volumes for polar analytes, and their narrow pH stability range. For these reasons, reversed-phase polymeric sorbents are also used frequently in environmental applications for the trace enrichment of soluble molecules that are not isolated by reversed-phase sorbents such as C18. 

Because of its higher pH stability, alumina and alumina-based stationary phases offer an alternative to silica and silica-based stationary phases. 

Although determination of a complete pH-degradation rate profile is desired, it may not always be practical due to limitations of drug supply and time. Also, insufficient solubility in purely aqueous systems may limit determination of pH-degradation rate profiles. Organic cosolvents may be used to increase solubility however, extrapolation to aqueous conditions must be done with caution. Stability of the drug in a suspended form in the desired buffer can be tested in lieu of solution stability. The stress test results must however, be interpreted in relation to the solubility in the suspension medium. The test may provide an empirical indication of pH stability in the presence of excess water. Satisfactory stability in the GI pH range (1 to 7.5) is important for oral absorption. While there are examples of... 

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