Gas-chromatographic analysis for cocaine in human plasma, with use of a nitrogen detector

We describe a procedure for measuring the concentra-tion of cocaine in plasma by gas chromatography, with use of a nitrogen detector. The procedure was tested on patients receiving intranasal cocaine for topical an-esthesia. The propyl ester of benzoylecgonine is used as an internal standard. The lower limit of sensitivity of the procedure is 5-10 tg of cocaine per liter of plasma. The coefficients of variation are 5.3 % and 3.0 % for concentrations of 50 and 100.tg/liter, respectively. Addftlonal Koyphrases: cocaine in urine #{149}drug assay #{149} preparation of n-propy! ester of benzoylecgonine #{149}“alkali flame ” detector As is the case for many alkaloids, post-use concen-trations of cocaine in plasma are both transient and low. Generally it is difficult to accurately measure drug concentrations of less than 100 tg/liter with a conventional flame-ionization detector, owing to its limited sensitivity and nonselective response to co-extracted endogenous constituents. This may explain why blood concentrations of cocaine in man have not been studied despite its widespread abuse as well as its importance as a local anesthetic. Most reports re-late to the detection or measurement of cocaine or of its major metabolite, benzoylecgonine, or both, in urine (1-4). This topic has been reviewed by Bastos and Hoffman (5). The dye-binding colorimetric pro-cedure of Woods et a!. (6), for many years the only procedure for measuring cocaine in blood, is 100-fold less sensitive than the procedure reported herein. By use of a selective nitrogen (“alkali flame”) de-tector, an increase in sensitivity is achieved that per-mits analysis of cocaine in plasma at concentrations as low as 5 zg/liter. This type of detector was origi-nally described by Karmen and Guiffrida (7)