Measurement of duloxetine in blood using high-performance liquid chromatography with spectrophotometric detection and column switching.

A method using high-performance liquid chromatography (HPLC) with column switching and ultraviolet (UV) spectroscopy was developed for the determination of duloxetine in human plasma. After centrifugation and addition of venlafaxine as internal standard, plasma samples were injected into the HPLC system and precleaned on a column (10 x 4.0 mm) filled with cyanopropyl (CN)-modified silica of 20 microm particle size, with use of 8% (vol/vol) acetonitrile in deionized water as eluent.