Rapid quantification of the delta-opioid receptor selective enkephalin DPDPE in canine cerebrospinal fluid by liquid chromatography--mass spectrometry.
An atmospheric pressure ionization liquid chromatographic-mass spectrometric assay was developed and validated for the determination of D-penicillamine(2,5) enkephalin (DPDPE) in cerebrospinal fluid (CSF) from dog. DPDPE and internal standard (D-Ala(2),D-Leu(5) enkephalin=DADLE) were isolated from CSF by reversed-phase C(18) solid-phase extraction with ZipTip micro-cartridges. Aliquots of extracted eluate were injected onto an Agilent Zorbax SB C(18) column (30 x 2.2 mm; 3.5 microm) at a flow-rate of 0.4 ml/min. The isocratic mobile phase of methanol-10 mM ammonium formate (pH 3) (75:25, v/v) was then diverted to waste for 45 s after injection, after which time flow was directed to the single quadrupole mass spectrometer. DPDPE was detected by positive mode selected ion monitoring. Standard curves were linear (r(2)> or =0.991) over the concentration range 1-1000 ng/ml. The efficiency of extraction recovery was greater than 97%, and the intra-assay and inter-assay precisions were within 9% relative standard deviation. DPDPE and the internal standard were stable in the injection solvent at 4 degrees C for at least 48 h. The assay was applied to the pharmacokinetic study of intrathecal DPDPE administration in the dog animal model.
Rossi
Steven
S
Department of Anesthesiology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0818, USA. ssrossi@ucsd.edu
Yaksh
Tony
T
D000701:Analgesics, Opioid / Q000134:cerebrospinal fluid* / Q000493:pharmacokinetics; D000818:Animals; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004285:Dogs; D020881:Enkephalin, D-Penicillamine (2,5)- / Q000134:cerebrospinal fluid* / Q000493:pharmacokinetics; D013058:Mass Spectrometry / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D000701:Analgesics, Opioid; D020881:Enkephalin, D-Penicillamine (2,5)-