Quantitative analysis of fentanyl in rat plasma by gas chromatography withnitrogen-phosphorus detection

A sensitive assay method was developed to determine fentanyl, an opiate ago nist, in rat plasma by gas chromatography with nitrogen-phosphorus detectio n. For the pretreatment of plasma samples, sodium hydroxide was added to de nature protein and n-butyl chloride was used to extract fentanyl. The calib ration curve was linear within the concentration range 0.5 to 50 ng/ml (r=0 .9997). The limit of detection was 0.1 ng/ml, and 0.5 ng/ml could be quanti fied with acceptable precision. Furthermore, fentanyl could be determined i n only 200 mul of rat plasma. The method has been successfully applied to a n intramuscular pharmacokinetic study at a dose of 10 mug/kg. Therefore, th e current method is a valuable analytical tool for investigating the pharma cokinetics of fentanyl at low clinical doses. (C) 2001 Elsevier Science B.V . All rights reserved.