Effective partition coefficient

An alternative method to overcome the solubility problem mentioned in the last section is to use bile salts to solubilize lipophilic molecules in the donor wells. Figure 7.51 shows a plot of relative permeability (Pe without bildPe with bile) versus membrane retention, which is related to lipophilicity (Section 7.7.2). As the plot shows, the most lipophilic molecules (carvedilol, propranolol, and verapamil) have attenuated permeabilities (by a factor of 3 in the case of carvedilol). The effective partition coefficient between the PAMPA membrane phase and the aqueous phase containing bile salt micelles [577] is expected to be lower for lipophilic molecules, which should result in lower Pe values. This is evident in the figure. 

The total concentration Cs is related to the nondissociated drug concentration C(0) at the apical membrane side by the effective partition coefficient, or... 

The term 0 + (l-0)D can be regarded as effective partition coefficient between the latest drop of extracted melt and total residue (residual solid + residual melt). Eq. (3.5) is the fundamental equation for dynamic melting. 

Freese, E., Levin, B.C., Pearce, R., Sreevalson, T., Kaufman, J.J., Koski, W.S., Semo, N.M. (1979) Correlation between the growth inhibitory effects, partition coefficients and teratogenic effects of lipophilic acids. Teratology 20(3), 413 140. 

Further, the erosion law factor K, defined in equation (4), regulates the age distribution of eroded material relative to the age structure of the crust. Thus for a given crust mass v. time curve, the three parameters E, R and K fully describe the crust formation and erosion history. In the present modelling E was varied between 0.2 and 1, R from 0.3 to 0.7, and K from 1.5 to 3.5. The approach used and the effective partition coefficients, as well as initial (meteori-tic) concentrations of the trace species are the same as those used by Kramers Tolstikhin (1997) and Nagler Kramers (1998). 

Ionization of the solutes to be separated greatly influences their chromatographic behaviour. If the effective partition coefficient has to be concentration-independent. ionization should be wholly suppressed or increased to a maximum or, alternatively, maintained at a steady level. Acids, alkalis and buffers are therefore often used as components of the partition system for ionizable substances. The addition of acid to a system with an aqueous stationary and organic mobile phase will decrease the relative migration Rp value) of an alkaloid. A base such as ammonia will increase the migration of an alkaloid in a comparable system. 

Usually the ion PNP has very low soluhility in the organic phases employed for extraction. Show that the effective partition coefficient for PNP in aU forms, k, o, is related to the partition coefficients kpnp.o for PNP and KpNp-,o for PNP hy... 

In the more common cases of partial liquid mixing with a boundary layer present near the freezing interface, an effective partition coefficient, 4,eff is defined as... 

From studies in zone melting, it is known that models of partial liquid mixing are more realistic, and the effective partition coefficient approach of equation (6.3.119) is quite useful. In this approach. 

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