UPLC–MS-MS Determination of Dihydrocodeine in Human Plasma and Its Application to a Pharmacokinetic Study

A sensitive and rapid ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS-MS) method was developed to determine dihydrocodeine (DHC) in human plasma using diazepam as the internal standard (IS). Sample preparation was accomplished through a liquid-liquid extraction procedure with ethyl acetate. The analyte and IS were separated on an Acquity UPLC BEH C18 column (2.1 × 50 mm, 1.7 μm) with the mobile phase of acetonitrile and 1% formic acid in water with gradient elution at a flow rate of 0.4 mL/min. The detection was performed on a triple quadrupole tandem mass spectrometer equipped with positive-ion electrospray ionization by multiple reaction monitoring (MRM) of the transitions at m/z 302.3 → 199.2 for DHC and m/z 285.1 → 193.1 for IS. The linearity of this method was found to be within the concentration range of 0.5-100 ng/mL with a lower limit of quantification of 0.5 ng/mL. The overall run time was 4.0 min. The method herein described was superior to previous methods and was successfully applied to the pharmacokinetic study of DHC in healthy Chinese volunteers after oral administration.