Relations between Phase Composition and Partition Coefficients for Some Neutral Steroids

Abstract

Information concerning partition coefficients in various solvent systems must he obtained before countercurrent distribution can be applied to the separation of neiitral steroid mixtures isolated from extracts of tissues and body fluids. From the many solvent mixtures available, the quaternary system consisting of ethyl acetate, cyclohexane, ethanol, and water w-as chosen. By suitable experimental design it was possible to measure partition coefficients over a wide range of phase cornpositions with relatively few cleterniinations. The data were then converted to a nomographic form. Nomograms for androsterone, 5-isoandrosterone, epiandrosteroae, dehydroepiandros terone, audrostanedione, Atandrostenedione, desoxycorticosterone, and 17-hydroxycorticosterone are reported. From the nomograms presented it is possible to predict the hehavior of these steroids i n countercurrent distribu tioii experiments. It is also possible to select systenis suitable for the separation of mixtures. In addition, this general approach may be found useful for the study of other types of solutes and other solvent systems. + increasing use of countercurrent distribution procedures THE for the separation of complex steroid mixtures (1, d, 4-6 8, 9, 14-16) makes it desirable to explore solvent systems which can be wed to accomplish these separations. Although an almost infinite number of solvent combinations is available, attention was focused on the quaternary, biphasic system consisting of ethyl acetate, cyclohexane ethyl alcohol, and water. These four solvents meet certain criteria which must be applied to any solvent contemplated for countercurrent distribution. These criteria are discussed by Craig and Craig (3) and include availability, ease of purification, adequate solubility of the solutes in the solvent system, a range of partition coefficients suitable for countercurrent distribution, and boiling points of the solvents in the range which permits easy isolation of the solute, as well as the assurance of a relatively constant phase composition throughout a distribution involving several hundred transfers. The partition coefficient, K , is defined as C,/Cl. where C, is the concentration of the solute in the upper phase and Cl is the concentration of the solute in the lower phase.In previous studies of the relation between phase composition and partition coefficients for some steroidal estrogens in ternary 50% il + 50% B 2 5 9 C + 7 5 7 -D 25% il + 75% B 2 5 7 C + 7591, D 75% A + 25Z-B 25% C + 75% D 25% 1 4 + 757, B 5070 -4 + 5OW0 B 7590 A + 25°C B _ _ .~~ 7541, C + 25W D 75% A + 2597, D Figure 1. Example of Experimental Design for Measurement of Partition Coefficients over a Wide Range of Phase Compositions i n a Quaternary Biphasic System The four components are A , B , C, and D and the percentages are by volume of the pure components prior to mutual saturation 757, C + 25% I)and quaternary blphasic solvent systems, It was found that the relationihip T V~E linear (10) with respect to the logarithm of the partition coefficient. I ...

Controlled-Cycle Operations Applied to Extraction Processes

“…The solvent system used throughout this work was the twophase mixture obtained by mixing 37.5% cyclohexane, 12.5% ethyl acetate, 35% ethyl alcohol, and 15% deionized water (all values are volume percentage). This type of solvent system was originally proposed by Engel et al (6) for the separation of steroidal mixtures. Pertinent physical characteristics of this solvent system are compared to those of the MIBK-acetic acid-water system in Table II.…”

The isolation of 3β-hydroxy-Δ5-steroids from the urine of normal men

“…Examination of the non-ketonic fraction This fraction was first distributed for 200 cycles by using the solvent system ethyl acetate-cyclohexane ethanol-water (2: 8: 3: 7, by vol.) described by Engel, Alexander, Carter, Elliott & Webster (1954). The modified Pettenkofer reaction described by Munson, Jones, McCall & Gallagher (1948), which has been shown to be fairly specific for 3fl-hydroxy-A5-steroids, has been used throughout the examination of the non-ketonic fraction to follow the degree of resolution obtained during the countercurrent distributions and chromatographic separations.…”