I am looking at protein precipitation as a method of sample preparation for the analysis of drugs in plasma samples. The samples will subsequently be analysed by LC/MS/MS using eg acetonitrile & formic acid/ammonium acetate in the mobile phase. The method needs to be as sensitive as possible. I would like to know the relative merits of using organic or acid for the precipitation.

Or SPE... All methods leave some background, which may result in ion suppression.