Abstract
A simple HPLC assay has been developed for free captopril in plasma and CSF, and for its mixed disulphides in CSF. Captopril is derivatized with p-bromophenacylbromide (p-BPB), and the adduct formed is extraced and then assayed using a reversed-phase column and UV detection. Captopril mixed disulphides are reduced with tributylphosphine to the free form which in turn is trapped with p-BPB. No clean-up procedures are necessary for this method which shows satisfactory accuracy and precision. A sensitivity level of 10 ng/mL has been reached for free total captopril in CSF, and for free captopril in plasma.