Ion Pair Extraction of Prostaglandin B2
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Studies ion pair extraction of prostaglandin B2 (PGB2). The apparent partition coefficient of PGB2 in chloroform-water system is in the order of 2 at pH 8, but a quantitative extraction was found to be possible when large hydrophobic amines are added to the system. A linear relationship was found between partition coefficients of amines in chloroform-water and octanol-water systems, quantitatively confirming previous studies. From the pH-profile of the PGB2 apparent partition coefficient, pka of PGB2 at I=0.1M and 25. was obtained. From a series of ion pair extraction studies employing 10 amines with PGB2, it is concluded that the assumption that the methylene groups are far enough removed from the polar groups to behave as if they are independent of them, is not warranted. Even though only limited thermodynamic data were obtained, there appears to be a change in mechanism in the temperature range of 5. to 43.