Improving extraction efficiency

[ankurhplc]

Dear Chromforum Users,

I am working on a drug which has a pka of something elevenish. I am trying to develop a assay on human plasma and found an extraction efficiency of about 42% with 100 % ACN (200uL plasma+2mL ACN) using liquid liquid extraction.
Can anybody suggest how can I improve the efficiency. My mobile phase composition is isocratic 59% ACN, 0.21mL/min FR. Anyideas about changing pH and any other ideas are welcome !!:)

Best Regards,
AS

[danko]

I wonder why you’re extracting your drug in/with 100% ACN. Is it really that soluble in 100 % ACN?

The 100% ACN can be reduced to 70-80% if its role is merely plasma precipitation.

You mentioned pKa, so it’s possible to ionize the compound, which will be my first move if I were you. That means you’ll have to include water in your extraction solvent, as well as some kind of pH control.
If I knew more about the molecule you’re dealing with I would probably have proposed more concrete actions. But I’m sure you’ll figure it out, provided you’re focusing on the compounds solubility.

Best Regards