QUANTITATIVE-DETERMINATION OF COCAINE, COCAETHYLENE (ETHYLCOCAINE), AND METABOLITES IN PLASMA AND URINE BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A sensitive HPLC assay was developed to quantitate the relatively nonp olar compounds cocaine, cocaethylene (ethylcocaine), norcocaine, and n orcocaethylene, as well as the relatively polar metabolites benzoylecg onine and benzoylnorecgonine, in rat plasma and urine. The assay in pl asma employed two successive liquid-liquid extractions and separate in jections onto two different columns (C-8 and C-18) to separate and qua ntitate the relatively polar and nonpolar compounds. In urine, the pro cedure employed a liquid-liquid extraction followed by solid-phase ext raction (C-18 light-load cartridges) and two separate injections as fo r plasma. The UV absorbance of the effluent was monitored at 235 nm. L inear standard curves were obtained over the concentration ranges of 2 5 to 1000 ng/mL and 5 to 250 ng/mL in plasma and urine, respectively. The inter- and intraday coefficients of variation for the assay of all compounds in plasma and urine were <18% at low concentrations (12.5-1 00 ng/mL) and <12% at high concentrations (125-250 ng/mL). There was n o degradation of these compounds during the extraction procedure or du ring 2 months of storage at -20 degrees C. The quantitation limits for the assay of the relatively nonpolar and polar compounds in plasma we re 25 (2.5 ng in 0.1 mL) and 50 ng/mL (5 ng in 0.1 mL), respectively. For the assay in urine, the quantitation limits were 5 (2.5 ng in 0.5 mL) and 12.5 ng/mL (6.25 ng in 0.5 mL) for the assay of the relatively nonpolar and polar compounds, respectively. The methods have been app lied to quantitate those compounds in rat plasma.