Abstract
Reliable, feasible analytical methods are needed for forensic and anti-doping testing of cocaine and its most important metabolites, benzoylecgonine, ecgonine methyl ester, and cocaethylene (the active metabolite formed in the presence of ethanol). An innovative workflow is presented here, using minute amounts of dried blood or plasma obtained by volumetric absorptive microsampling (VAMS), followed by miniaturized pretreatment by dispersive pipette extraction (DPX) and LC-MS/MS analysis. After sampling 20 µL of blood or plasma with a VAMS device, the sample was dried, extracted, and loaded onto a DPX tip. The DPX pretreatment lasted less than one minute and after elution with methanol the sample was directly injected into the LC-MS/MS system. The chromatographic analysis was carried out on a C8 column, using a mobile phase containing aqueous formic acid and acetonitrile. Good extraction yield (> 85%), precision (relative standard deviation, RSD < 6.0%) and matrix effect (< 12%) values were obtained. Analyte stability was outstanding (recovery > 85% after 2 months at room temperature). The method was successfully applied to real blood and plasma VAMS, with results in very good agreement with those of fluid samples. The method seems suitable for the monitoring of concomitant cocaine and ethanol use by means of plasma or blood VAMS testing.
Highlights
Cocaine (methyl (1R,2R,3S,5S)-3-benzoyloxy-8-methyl-8-azabicyclo[3.2.1]octane-2-carboxylate,Figure 1a, COC) is a natural psychoactive alkaloid extracted from the leaves of the Erythroxylum coca plant
The dispersive pipette extraction (DPX) pretreatment lasted less than one minute and after elution with methanol the sample was directly injected into the LC-MS/MS system
The first step of the study was the testing of volumetric absorptive microsampling (VAMS) volume accuracy for plasma sampling, followed by the development of a suitable pretreatment procedure
Summary
It is considered one of the most frequently consumed drugs of abuse, with more than 15 million people currently using this substance worldwide, and with the highest prevalence reaching 2.4% in England and Wales [1]. Exhaustion, somnolence, irritability, and judgment impairment are typical short-term effects, while stroke or ictus, paranoid psychosis and mucosal necrosis can appear over the long term [3,4]. For these reasons, COC is included in the lists of controlled substances of most States [5,6].
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