Aqueous solubility characterization

When a NAPL reaches the subsurface, it may by subject to mechanical forces that lead to the formation of a mixed NAPL-water micro-/nanoemulsion characterized by the presence of micro- and nanodroplets of organic compounds. These micro- and nanoemulsions are transparent or translucent systems, kinetically (nano-) or thermodynamically (micro-) stable, and display an apparent increase in aqueous solubility as compared to the intrinsic solubility of the NAPL itself (Tadros 2004). The very small droplet size (50-200 nm in the case of a nanoemulsion) causes a large reduction in the force of gravity, enabling the system to remain dispersed and... 

The synthesis and characterization of isolated, isomerically pure a2-[P2W17061(Mn+ L)]y- (Mn+ = Mn3 +, Fe3+, Co2+, Ni2+, and Cu2+) as aqueous-soluble potassium salts (L = HzO) and as the more novel, organic-solvent-soluble tetrabutylammonium salts (L = Br) are described herein. These preparations yield mono-metal-substituted complexes of the Dawson 2 isomer, 2-[P2Wi7O6i]10, that are typically >98% free of the (Xi isomer.1,2 The X-ray crystallographic structures of the a2-[P2W17O61]10 lacunary precursor and the a2-[P2W17061(Co" OH2)]8- complex are known.3... 

It is important to characterize the physicochemical properties of the suspensions well, so that the PK data can be interpreted appropriately. Typical characterization of the drug substance includes purity, residual solvents, aqueous solubility pro Lie (pH 2, FaSSIF), crystallinity (XRPD/DSC), particle size, pl and logP. For solution formulations at various stages of discovery studies, dose analysis is essential, and for efLcacy assessment and toxicology studies, chemical stability for the... 

Following oral administration, dissolution of the drug molecule in the intestinal milieu is a prerequisite for the absorption process. According to the Biopharmaceutical Classification System (BCS) [2], poor water-soluble compounds (i.e., aqueous solubility less than 100 pg/ mL) are class 2 or class 4 compounds. For class 2 compounds, the absorption level is dictated by the dissolution properties of the molecule in the gastrointestinal (GI) fluids. BCS class 4 compounds, which are characterized by both low solubility and poor intestinal wall permeability, are generally poor drug candidates (unless the dose is very low). 

Figure 15.12. XH NMR spectra of aqueous soluble species from (A) coarse air particles with diameters of 33-4.7mm (pH 6.55) (B) fine air particles with diameters of 0.65-1.1 mm (pH 3.92). Compounds identified in the spectra include 1, acetic acid 2, monomethylamine 3, succinic acid 4, dimethylamine 5, methanesulfonic acid 6, methanol 7, monomethyl hydrogen sulfate 8, hydroxymethanesulfonic acid 9, phthalic acid 10, terephthalic acid. Reprinted from Suzuki, Y., Kawakami, M., and Akasaka, K. (2001). JH NMR application for characterizing water-soluble organic compounds in urban atmospheric particles. Environ. Sci. Technol. 35, 2656-2664, with permission from the American Chemical Society.

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