Here, both a solubility enhancement and a solubility decrease occur. Impurities can also affect the solubility of a solute of interest. Also, usually a combination of different analytical techniques is necessary to obtain both the solubility and the identity of the solid phase in equilibrium. Experimental determination of solubilities is a tedious and time-consuming work and requires a sufficient amount of substance that is often not available in an early stage of development. Often one faces a lack of consistent solubility data for the substance of interest. Even more hard to find are ternary solubility phase diagrams that describe equilibria of two substances in a solvent such as the target compound and an impurity in a solvent of choice or the two enantiomers of a chiral system in a solvent. However, often the phase diagrams required are not known in particular for new substances in the fine chemical and pharmaceutical fields. 16.32 Ternary solubility diagram showing the temperature dependence of the phase behaviour of ethyl acetate/ water/ethanol, indicating that the ternary azeotrope is two phase at 20 ☌ and single phase at 70 ☌. 16.6 Ternary solubility diagram for -propanol/water/cyclohexane (% w/w, 35 ☌).įig. 16.5 Ternary solubility diagram for n-propanol/water/n-propyl acetate (% w/w, 30☌).įig. The solubility phase diagram of a conglomerate (Fig. The theoretical ternary solubility phase diagrams of racemates are represented by Fig. The solubilities of the two enantiomers are identical in an achiral solvent. The dissolution rate is proportional to the solubility, regardless of dissolution mechanism. When the rate of drug absorption is controlled by the dissolution rate, the bioavailability of a drug increases with an increase of its dissolution rate. At present, using a cubic equation of state or a lattice-gas equation appears to offer the best compromise between accuracy and ease of application. As the equations describing molecular interactions in dense fluids become more accurate, we can expect our abilities to model complex phase behavior to improve.
As Johnston has pointed out (Wong, Pearlman, and Johnston, 1985 Johnston, Peck, and Kim, 1989), no single model will work for all situations.
#TWO PHASE REGION TERNARY DIAGRAM HOW TO#
This chapter demonstrates how to calculate phase diagrams and solubility isotherms for binary and ternary supercritical mixtures. It is obvious that lowering the solvent cost, conforming to air pollu. įollowing the technique of solvent selection by solubility maps and ternary solubility diagrams, the coatings formulator can adapt solvent blends for epoxy resins to obtain lower viscosities and improved drying rates. Special Effects Accomplished by Formulating with Ternary Solubility Diagrams.
The results obtained by Kumok and Batyreva are therefore mentioned in Chapter V but not accepted.
This comment applies in particular to the calculations performed on data from ternary solubility diagrams. The way in which the solubility products were evaluated from the primary data could not be followed in such detail that a critical evaluation could be made. The drug solubility response is linear in the A concentration in this case. The composition of the solute is the constant concentration of B, the concentration of A in the abscissa, and the complement concentration of the third component. (Inset) Concentration of drug in compositions with constant concentration of B. 3 Ternary diagram of solubility of a compound in a ternary mixture with linear solubility response. In addition to melting point phase diagrams, ternary solubility phase diagrams, in which the third compound is a liquid solvent, may also be applied to classify racemates (Fig.
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