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Hello all,
I'm currently working on the formulation of a novel compound that has an oily physical state at room temperature. In an effort to determine how pH adjustment might affect solubility I assayed the compound in various buffers ranging from pH 2-12 (an excess of compound in ~1mL of buffer, and the solution was allowed to equilibrate on a rotator for 5-7 days). I was going to filter the samples when I realized that the excess oily compound in the vials will also go through the filters. I'm also unable to pipette the aqueous solution out of the vials without "contaminating" the samples for analysis with the oily compound. Any suggestions for a more reliable assay?
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Daer AJ Beaupre,
If your compound dissolves well in an organic phase, but not in water,
you could try a two phase liquid extraction under various pH conditions.
E.g. chloroform and water, with various buffers in your aqeous phase.
Determination of your compound in both phases will tell you something
about pH dependency of solubility in aqeous and organic phases.
Sincerely,
Rob ter Heine
---
Rob ter Heine, PhD, PharmD
Meander Medical Center, hospital Pharmacy
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If the oily compound is heavier than water, you should be able to
centrifuge the containers to separate buffer from compound.
Regards,
Paul.
--
Paul Hurley
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AJ
Put it in a separatory funnel and draw the aqueous off the bottom.
Dale
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Dear Beaupre,
You can generate pH solubility profile of an oily compound using potentiometric titration by using instruments like glpKa or PCA 200. You may need to dissolve your compound in a hydro-organic composition (at various concentrations) and run a pKa analysis and use this as input parameter for intrinsic solubility experiment. You may have to use the data to extrapolate it to zero organic solvent content using yashoda yalkowsky algorithm and software will enable you to get the profile.
Hope it will help.
Vaibhav
Pharm Dev,
Aurigene Discovery Technologies Limited
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