HPLC determination with fluorimetric detection of venlafaxine hydrochloride in human plasma and its application to bioequivalence studies

Objective:To establish an HPLC-fluorimetric detection method for determination of venlafaxine hydro- chloride in human plasma.Methods:Separation was achieved on Diamonsil C_(18)column(150 mm×4.6 mm,5μm) with the mobile phase of acetonitrile-phosphate buffer solution(pH 3.0)-triethylamine(33.5:66.5:1)at the flow rate of 1.0mL·min~(-1).The injection volume was 20μL and the internal standard was maprotiline.Plasma samples were extracted with n-hexane and isopropyl alcohol,and then detected by fluorimetric detection(λ_(ex)=276 nm,λ_(em)=596 nm).Results:The linear range of venlafaxine hydrochloride in human plasma was 10-800 ng· mL~(-1)(r=0.9999).The lowest detectable concentration was 2 ng·mL~(-1)and the lowest detectable plasma concen- tration was 16.99ng·mL~(-1)(S/N3).The extraction and method recoveries(n=5)of plasma concentration 30, 150,600 ng·mL~(-1)were 81.51%-91.08% and 98.7%-112.6%,respectively.The RSDs(n=5)of within- day and between-day were less than 12% and 10%,respectively.Conclusion:The method is accurate,sensitive, rapid,reproducible,and can be applied to determine the concentration of venlafaxine hydrochloride in human plas- ma.