Cocaine LC-MS Analysis in Insects for the Determination of Post-Mortem Interval

More than 24,000 persons in the U.S. died from cocaine-involved overdose in 2021. In cases of homicide and suspect death, the estimation of postmortem interval (PMI), which represents the time elapsed since death and body discovery, is crucial and usually involves the use of insects when human tissues are severely decomposed, or inadequate for sampling. Diptera: Calliphoridae, commonly known as blow flies, are the primary colonizers of human corpses, making them useful for entomotoxicology research. In this project, a sensitive and selective method using reverse-phase high-performance liquid chromatography/time of flight mass spectrometry (RPHPLC/TOF-MS) was developed for the simultaneous screening and quantification of cocaine and its metabolites in the developmental stages of Calliphora vicina Robineau-Desvoidy, 1830 (Diptera: Calliphoridae). A homogenization process employing zirconia beads, followed by a precipitation step with ice-cold acetonitrile, was utilized for the extraction of cocaine from the insect specimens. RPHPLC/TOF-MS analysis resulted in instrumental limits of detection (LODs) of 1 and 8 ng/mL for cocaine and benzoylecgonine, respectively. Thus, this analytical method can be employed in forensic investigations for the estimation of the PMI.