Simultaneous determination of cocaine, ecgonine methyl ester, benzoylecgonine, cocaethylene and norcocaine in dried blood spots by ultra-performance liquid chromatography coupled to tandem mass spectrometry.

Cocaine (COC) is one of the most widely abused drugs in the world and its sensitive and its reliable measurement in blood is of great importance in the field of forensic and clinical toxicology. Additionally, the determination of COC metabolites such as benzoylecgonine (BZE), cocaethylene (CE), ecgonine methyl ester (EME), and norcocaine (NCOC) are also of complementary diagnostic value. The quantification of COC and metabolites in dried blood spots (DBS) may be an alternative to conventional collection methods with several advantages, including easier, on-site, collection, transportation and storage. In this study, we present a simple and comprehensively validated UPLC-MS/MS assay to measured COC, BZE, EME, NCOC and CE in DBS. The evaluated assay was linear from 5-500 ng mL-1. Precision assays presented CV% of 1.27-6.82, and accuracy in the range of 97-113.78%. Low haematocrit values had a negative impact in the assay accuracy. COC, BE, NCOC and CE measurements can be made reliably in DBS stored for 14 days at room temperature, as well as at -20 °C and 45 °C. All evaluated compounds can be measured in DBS maintained at -20 °C for 14 days. DBS sampling can be used for the clinical evaluation of the exposure to COC, being an alternative for collection, short-term storage and transportation of blood at room and high temperatures.