Partial validation for the analysis of benzoylecgonine and opiates in urine using solid phase extraction and GC/MS

Abstract

In recent years an increase in drug use amongst Maltese locals has been observed, particularly in relation to the use of cocaine, cannabis and new synthetic drugs. This is also supported by the increased availability of these substances. Such developments have led to the need to develop analytical methods which detect such substances in biological fluids within reasonable timeframes for legal and medical purposes. The drugs of abuse reported most frequently among frequent users and in overdose emergencies at Mater Dei Hospital (MDH), the major teaching hospital in Malta include heroin and cocaine. This study aimed to validate techniques for the analysis of benzoylecgonine (major metabolite of cocaine) and opiates in urine, using solid phase extraction and GC/MS using commercially available test kits developed by Eureka Lab Division, used at facilities in the Department of Chemistry. Calibration curves congruent with those available with these kits were produced. After partial validation of the method was completed, this was confirmed using anonymised urine samples collected post-mortem. Any drugs/metabolites from these urine samples were extracted via Solid Phase extraction using the Eureka® kits. They were subsequently concentrated with nitrogen and analysed via GC/MS to identify and possibly measure the levels of drugs/metabolites determined in the sample. Following the relevant Ethics approval urine samples obtained from six cadavers of suspected drug overdose were analysed to validate the procedure. All analytes were successfully detected in these six urine samples. Interday accuracy was 37.4% at low concentration and 19.49% at high concentration for benzoylecgonine; 8.56% at low concentration and 11.19% at high concentration for cocaethylene; 40.84% at low concentration and 11.31% at high concentration for cocaine; 19.70% at low concentration and 48.90% at high concentration for morphine and 23.42% at low concentration and 11.98% at high concentration for morphine. These results indicate that this analytical method resulted in the partial validation for the analysis of benzoylecgonine and opiates in urine using solid phase extraction and GC/MS. This analysis was undertaken with relative ease, efficacy, cost and time needed as compared to traditional liquid-liquid extraction, which facilitates its use in forensic and clinical laboratories and in rehab centres.