protein precipitation method,Internalstandard plasma merging

[nageshiict]

I am facing one problem regarding protein precipitation method. I am doing chiral separation of anti depressant analyte and its metabolite with ISTD by a chiral Chirobiotech V column in polar organic mode by using flourascence detector. I have tried protein precipitation method by ACN,ACN+ZnSO4, HClO4. But some what Plasma peak is merging with ISTD in all of these precipitation methods. please suggest me regarding this to follow.

[Kostas Petritis]

Maybe you can try Acetone/methanol or sulfosalicilic acid precipitation?

[Uwe Neue]

Or you could do better sample preparation using a well established SPE technique. Look at the Waters webside for the Oasis applications booklet.