Specificity dissolution

This process occurs only at the silver nanoparticles of which resonance wavelength is in accordance with the incident light wavelength. Therefore, size-specific dissolution is possible (processes bl-b3 in Figure 2). 

M Bisrat, C Nystrom. Physicochemical aspects of drug release. VIII. The relation between particle size and surface specific dissolution rate in agitated suspensions. Int J Pharm 47 223-231, 1988. 

A general chapter giving the dissolution test for solid oral dosage forms was first described in the EP in 1991 (20). As mentioned above, the EP has no product monographs in which to elaborate specific dissolution procedures. 

In conclusion, it appears necessary to study more extensively those properties of the various oxides, which determine their specific dissolution behaviour. As pointed out by Postma (1993), the variation in reactivity, a solid phase parameter, may, in some cases, be twice as high as the effect of the type of dissolution (protonation, complexation, reduction). 

A 1990 study by Sheikh and Fordlran (Baylor University Medical Center) indicated that there arc important differences in the bioavailabilily of calcium from different calcium-containing compounds. The ability lo dissolve a preparation in dilute acid is a major factor that contributes to bioavailability. Currently, the FDA tFood and Drug Administration. U S.) does not require commercially available products to meet specific dissolution standards. 

Once the crack is initiated, the metal surface inside the crack may be quite different from the normal surface of the metal. Thus, in the course of plastic deformation, the metal could have developed slip steps [see Fig. 12.77(c)] which contain crystallographic planes of high Miller index at which the specific dissolution rate (or exchange current density) may be larger than that at the normal metal surface. Anodic current densities of some 104 times those at a passive surface have been shown to appear at a metal surface that is yielding under stress (Despic and Raicheff, 1978). 

Empirical models predicting the rates of mineral-specific dissolution as a function of pH are summarized within the section on mineral composition in an attempt to provide a useful database for predicting dissolution rates for both laboratory and field systems. Equations describing near-equilibrium mineral dissolution and precipitation rates are summarized in the section on chemical affinity. 

Figure 7. Species-specific dissolution of isolated VEs by purified lysins as determined by the light scattering assay. Vertical axis, percent VE dissolved horizontal axis, qg lysin added. R j, VEs from the red abalone, H. rufescens. B j, VEs from the black abalone, H. cracherodii. Pyj, VEs from the pink abalone, H. corrugata. ( ) red lysin (A) pink lysin and ( ) black lysin (from Vacquier and Lee, 1993).

The specific dissolution rate constant (iCi) is a constant for a specific set of conditions, although it is dependent on temperature, viscosity, agitation or stirring (which alters the thickness of diffusion layer) and volume of the solvent. 

Figure 8.3 Noyes-Whitney dissolution rate law. dC/dt, dissolution rate of a drug K, dissolution rate constant D, diffusion coefficient h, thickness of the diffusion layer S, surface area of the undissolved solid drug Q, solubility of drug in solvent C, concentration of drug in gastrointestinal (Gl) fluid Q - C, concentration gradient fC), specific dissolution rate constant.

For quality control purposes, dissolution testing is a means of ensuring batch-to-batch consistency and compliance with specifications. Dissolution rate may be able to highlight whether any serious changes or faults have occurred in the formulation, manufacture, or storage of a product. 

It is suggested from the images of the LB film that comparing the two electrolytes their influence originates from different mechanisms. The interaction of an aqueous solution of NaCl with cadmium arachidate is probably a specific dissolution-type effect, which might be initiated at the pinholes or defects of the ordered layer. The results of XPS surface analysis also supported that the removal of cadmium arachidate by NaCl solution is... 

Most materials contain several metal components. Some of their dissolution characteristics may be understood by the properties of these alloy components, which follow their very specific dissolution kinetics. However, the formation of single-phase alloys often involves a serious change of the chemical properties similar to the formation of compounds. These alloys cannot be treated as a simple mixture of the metal components due to their possible chemical inter-... 

Absorption into the blood depends on the physicoehemical form of the radionuclide deposited in the respiratoiy system, but is taken to be independent of deposition site, with the exception of ETj, from which no absorption is assumed. The model allows for changes in dissolution and absorption into blood with time. The use of material specific dissolution rates is recommended, but default absorption parameters are given for use when no specific information is available, namely types F (fast), M (moderate) and S (slow). These correspond broadly to the Pubhcation 30 default lung classes D (days), W (weeks) and Y (years) respectively, although the lung classes referred to overall clearance rates from the lung. 

PSBs and intense slip bands are very prone to specific dissolution, not only for passivated alloys but also in conditions of generalized dissolution as shown in Figure 7 for copper single crystals in NaClO solution [9]. 

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