A quantitative selected ion monitoring assay for ketoprofen determination in human biological fluids.

A new very sensitive method of ketoprofen [(benzoyl-3-phenyl) 2-propionic acid] determination in various biological fluids using selected ion monitoring is described. After ether extraction is acidic medium, ketoprofen and (benzoyl-4-phenyl)-2-butyric acid used as internal standard are methylated and their concentrations determined by monitoring the m/z values correponding to their respective molecular ions. Standard deviation is below 5% at 100 ng ml-1. Detection limits range from 10 ng ml-1 for urine and serum samples to 50 ng ml-1 for maternal milk specimens. This method has been applied successfully to various biological studies: pharmacokinetic profiles, bioavailability and transfer of the drug through physiological barriers.