Pre‐column derivatization method for determining phenylephrine in human plasma and its application in a pharmacokinetic study

In the present study, a rapid derivatization liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated to evaluate phenylephrine in human plasma. The plasma samples were processed to precipitate the proteins, followed by derivatization of the phenylephrine in the plasma with dansyl‐chloride solution and extraction with methyl tert‐ butyl ether– n ‐hexane (2:1, v/v). The treated samples were analyzed on a Gemini C 18 column with 3 min gradient elution, and sensitive detection was achieved with a Waters TQ‐s. The method gave linear results over a concentration range from 0.020 to 10.0 ng/ml. The lower limit of quantification was 0.020 ng/ml. Intra‐ and inter‐day precision was <15%, and accuracy was 95.0–105.3%. The validated LC–MS/MS method was successfully applied in the pharmacokinetic analysis of phenylephrine in Chinese subjects with common cold after a single‐dose administration of 5, 10 or 20 mg phenylephrine. This pre‐column derivatization method may also be applied for the analysis of endogenous hormones such as norepinephrine and adrenaline in a biological matrix.