Soluble release

Water Soluble Released drug-PLGA oligomer conjugates... 

Based on the knowledge of the substance solubility, release mechanisms from the dosage forms and known interactions with key excipients, certain components may be of special importance to include or exclude in the dissolution test medium. This has to be considered on a case-by-case basis. Two examples are given below. 

Two different approaches to the problem of releasing deposited alloy films have been assessed. One is to use a polymeric substrate that can be dissolved in a suitable solvent, while the other is to choose a solid substrate to which the deposited film adheres very poorly so that it is easily lifted off. Yet another procedure is to coat a polymeric film such as Kapton with a water-soluble release agent such as sodium iodide or barium chloride. There are many other such possibilities. 

Water column model. A comprehensive chemical mass balance in the water column should account for mass change with time, advection and dispersion, particle deposition, soluble release, particle resuspension from the bed, evaporation to air and degradation. Over a differential distance x in the direction of flow (L) these processes are. 

What follows is a theoretical underpinning of the non-particle resuspension, soluble release processes represented by Eq. 3 and 4. A broad approach will be taken in that numerous transport processes will be considered. These will include the individual processes plus several combined processes that operate in series or parallel on both sides of the interface. 

The overall mass-transfer coefficient. As shown above the resistance-in-series concept provides a means for combining transport processes on either side of the interface. Defined as the ratio of the flux to the concentration on particles, Ks, the overall sediment soluble release mass-transfer coefficient (L/t) is... 

CFaT riverine models were presented for both the water column and bed sediment. They were then simplified to focus onto the non-flow resuspension soluble fraction using the quasi-steady state assumption to isolate the key water-side and sediment-side process elements. Field evidence of soluble release based on CFaT model derived data was reviewed for three rivers. Both the traditional particle background resuspension process and more recent soluble fraction process algorithms data interpretation were covered. Numerical field calibrated resuspension velocities and soluble mass-transfer coefficients were presented. Candidate water-side and sediment-side transport processes, selected from the literature were reviewed. Those that provided the best theoretical explanation and contained laboratory and/or field data support were selected. Finally, the flux and the overall transport coefficient which captures the essential features of the framework were presented. Following this the theoretical mass-transfer coefficients were applied to a site on the Fox River below De Pere Dam. Numerical calculations were made for the transport coefficients for both individual and combined processes. 

Thibodeaux, L.J. 2005. Recent advances in our understanding of sediment-to-water contaminant fluxes. The soluble release fraction. Aquatic Ecosystem Health Management, 8(1) 1-9. 

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