Liquid chromatographic determination of cocaine, benzoylecgonine, and cocaethylene in whole blood and serum samples with diode-array detection

An extraction with Bond Elut Certify solid-phase extraction (SPE) columns is developed for the isolation of cocaine, benzoylecgonine, and cocaethylene from whole blood and serum followed by reversed-phase liquid chromatography with diodearray detection. Two internal standards (2′-methylbenzoylecgonine and 2′-methylcocaine) with close structural resemblance to benzoylecgonine (a carboxylic acid) and to the two esters, cocaine and cocaethylene, are used in the analytical procedure. A thorough evaluation of this SPE and a comparison with different liquid-liquid extractions clearly show the superiority of the SPE. A linear response (correlation coefficient greater than 0.998) over a broad concentration range (0.025-5.0 μg/mL) is obtained. The sensitivity, specificity, precision (coefficients of variation less than 4.9% for within-day reproducibility and less than 5.3% for total reproducibility), and accuracy of the method are excellent for each analyte. Forensic blood samples from people suspected of cocaine abuse are analyzed and show the usefulness of the method, even for degraded postmortem samples.