Abstract: OcjectiVe High performance liquid chromarography ( HPLC ) method was established for determination of remifentanil in plasma. The study will provide academic foundation for the development and clinical use of remifentanil. Methods The samples eXtracted with 1-chlorobutane and supernatant was back eXtracted into 0. 01mol/L HCl again. The separation was performed on a spherisorb-CN column with a mobile phase of 0. 02mol/L-1NaH2 PO4-acetonitrile( 70: 30 ) including 0. 01%triethylamine at a flow rate of 1. 5mL/min. The column temperature was room temperature,the detection-wavelength was 210nm and 200μL of solution was injected into HPLC. Eight patients undergoing thoracic surgery were assigned to receive remifentanil target controlled infusion( TCI )( 6μg/L ) and propofol intravenous injection(2. 5mg/kg). Arterial blood samples were taken before and after TCI remifentanil 5, 10,20,30,60,90 min for measuring of blood concentration of remifentanil by HPLC. Results A linearity was obtained from 2 . 5μg/L to 300μg/L of remifentanil in plasma with a good correlation( r=0 . 999 1 ). The between-day and within-day RSD% were less than 10%. The eXtraction recoveries were more than 78 . 57%,and the method recoveries were between 96 . 03% and 104 . 67%. The determination of the concentration was lower than target plasma concentration at TCI 5 min to 20 min( p<0 . 05 )and there was no significant difference from 30 min to 90 min( p >0 . 05 ). Conclusion This HPLC method is simple,sensitive and accurate,and it is suitable for routine determination of remifentanil levels in human plasma.

Key words: remifentanil, plasma, chromatography, high pressure liquid