Physicochemical basis

Emphasis was put on providing a sound physicochemical basis for the modeling of the effects determining a reaction mechanism. Thus, methods were developed for the estimation of pXj-vahies, bond dissociation energies, heats of formation, frontier molecular orbital energies and coefficients, and stcric hindrance. 

A. P. MacKenzie, The physicochemical basis for the freeze-drying process Dev. Biol. Stand., 36, 51-67 (1977). 

Physicochemical Basis of Quantitative Determination of Anionic Surfactant Concentrations by Using an Autotitrator... 

The physicochemical basis behind the technique of radiocarbon dating is the isotopic abundances of carbon s three isotopes 12C is the normal form and constitutes 98.9 per cent of all naturally occurring carbon. 13 C is the other naturally occurring isotope, with an abundance of about 1 per cent. 14C does not occur naturally, but tiny amounts of it are formed when high-energy particles from space collide with gases in the upper atmosphere, thus causing radiochemical modification. 

Since reversed-phase HPLC is the most commonly used technique in HPLC, it would be a good idea to develop a better understanding of separation mechanisms. The reader would benefit from the basic review on physicochemical basis of retention in HPLC (see Chapter 2, reference 5). 

Levy G, Hayes BA. Physicochemical basis of the buffered acet-ylsalicylic acid controversy. N Engl J Med 1960 262(21) 1053-1058. 

Humberstone AJ, Porter CJ and Charman WN (1996) A Physicochemical Basis for the Effect of Food on the Absolute Oral Bioavailability of Halofantrine. J Pharm Sci 85 pp 525-529. 

Serajuddin, A.T.M., Sheen, P, Mufson, D., Bernstein, D.F., and Augustine, M.A., Physicochemical basis of increased bioavailability of a poorly water-soluble drug following oral administration as organic solutions, /. Pharm. Sci., 77, 325, 1988. 

The relevance of LSC data to reverse osmosis stems from the physicochemical basis (adsorption equilibrium considerations) of liquid-solid chromatography (52), and the principle that the solute-solvent-membrane material (column material) Interactions governing the relative retention times of solutes in LSC are analogous to the interactions prevailing at the membrane-solution Interface under reverse osmosis conditions. The work already reported in several papers on the subject (53-58) indicate that the foregoing principle is valid, and hence LSC data offer an appropriate means of characterizing interfacial properties of membrane materials, and understanding solute separations in reverse osmosis. 

As we shall see later, the quantum yield of a substance can be greatly influenced by the fluorophore s immediate environment. Likewise, shifts in the emission spectrum can also help one to detect changes in environment, and the physicochemical basis of such changes can often be inferred. 

Huang, W. M. and. Tso, P O. P. (1966). Physicochemical basis of recognition process in nucleic acid interactions. I. Interactions of polyuridylic acid and nucleosides. J. Mol. Biol, 16, 523. 

To accommodate some or all of these phenomena, several alternatives to the occupation theory have been proposed. None of them is entirely satisfactory, and some have no physicochemical basis. 

Current practices in analytical SFE are organized into off-line and on-line procedures, despite their common physicochemical basis. Off-line SFE, the current method in fashion, offers more flexibility with respect to extracting different sample sizes and types, as well as in the choice of the final analytical method. On-line procedures are usually combinations of SFE with ancillary techniques such as GC, LC, supercritical fluid, or gel permeation chromatography. 

Wilce, M.C J., Aguilar, M.-L, and Heam, T.W. 1995. Physicochemical basis of amino acid hydrophobicity scales Evaluation of four new scales of amino acid hydrophobicity coefficients derived from RP-HPLC of peptides. Anal. Chem. 67 1210-1219. 

Werner, H., Herein, D., Schulz, G. et al. (1997) Catalysis Letters, 49, 109-119. Slin ko, M.M. and Jaeger, N.I. (1994) Physicochemical Basis for the Appearance of Self-Sustained Oscillations in Heterogeneous Catalytic Systems, Elsevier. 

Humberstone, A. J., C. J. H. Porter, and W. N. Charman. 1996. A physicochemical basis for the effect of food on the absolute oral bioavailability of halofantrinJePharm. Sci85 525-529. 

Albert, A., Selective Toxicity. The Physicochemical Basis of Therapy. Chapman and Hall, London, 1979, p. 23... 

W.A. Vance et al., Disubstituted amino-, nitroso-, and nitrofluorenes A physicochemical basis for structure-activity relationships in Salmonella typhimurium. Environ. Mutagen. 9, 123-141 (1987)... 

Timasheff, S.N. (1992). A physicochemical basis for the selection of osmolytes by nature. In Water and Life A Comparative Analysis of Water Relationships at the Organismic, Cellular, and Molecular Levels, pp. 70-84, ed. G.N. Somero, C.B. Osmond, and C.L. Bolis. Berlin Springer-Verlag. 

The logarithmic expression in the definition of AP has no physicochemical basis and is used for numerical reasons only pH= 6.5 was selected as the representative pH of small intestines, where most of the absorption of drugs takes place. The incorporation of the terms Pc and fun in the numerator of (6.2) means that the pH-partition hypothesis governs gastrointestinal absorption. Plausibly, AP was considered proportional to solubility and inversely proportional to the dose in accord with classical dissolution-absorption considerations. The volume term V corresponds to the small-intestinal volume content, which was set arbitrarily... 

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