Determination of [3H]brifentanil, a potent narcotic analgesic, from rat serum by high-performance liquid chromatography with on-line radioactive detection.

A method for rapid analysis of [3H]brifentanil extracted from rat serum is described that has the advantages of sensitivity, speed and specificity. The method is based on extraction from serum via solid-phase extraction followed by chromatographic separation on a reversed-phase high-performance liquid chromatographic column. Detection of [3H]brifentanil is accomplished with an on-line radioactive detector, thus the laborious step of peak collection and subsequent liquid scintillation counting is eliminated. The developed method is sensitive to 0.1 ng/ml and has been successfully applied to pharmacokinetic studies in rats. In vivo metabolites retaining the radiolabel have been detected with the method and were more polar than the parent compound as based upon the elution order on the reversed-phase system.

Sensitive method for the determination of pentamorphone in serum by liquid chromatography-mass spectrometry with thermospray interface.

A liquid chromatographic-mass spectrometric method for the determination of 14-beta-n-pentylaminomorphinone (pentamorphone) and 14-beta-n-pentylaminocodeinone (PAC) as internal standard is developed. Concentration levels in serum were calculated by the ratio of the peak areas of pentamorphone to PAC versus the concentration of pentamorphone. Peak areas were measured using selected-ion-recording of the pseudo-molecular ions of pentamorphone and PAC (m/z 369 and m/z 383, respectively). Aliquots (50 microliters) of sample were injected on a C18 mu Bondapak column following solid-phase extraction. The lowest limit of quantitation observed was 43 pg/ml. The sensitivity, accuracy and reproducibility of the method were demonstrated to be satisfactory for application in pharmacokinetic study of pentamorphone.