Analysis of cocaine and its metabolites in human urine

In our country, the development of appropriate forensic toxicological methods to detect substances that can be abused in biological material of postmortem and/or living organisms is highly important both in terms of medical and legal aspects. In our study, three different methods(Methods A,B and C) was developed towards the extraction and derivatization steps prior to chromatographic analysis in order to be able to perform the analysis of cocaine and its metabolites cocaethylene and benzoylecgonine in human urine by using gas chromatography/mass spectrometer(GC/MS). A fast, simple liquid-liquid extraction(LLE) technique was performed to isolate cocaine, cocaethylene and benzoylecgonine from human urine, no derivatization was applied before the chromatographic analysis in Method A. Samples were extracted with petroleum ether in the performed extraction technique. After a one-step preliminary step, benzoylecgonine could not be detected while cocaine and cocaethylene could be detected in the samples analyzed by GC/MS. In Method B, the same LLE technique as in Method A was performed to the samples and then the samples were derivatized using the different derivatization mechanisms(silylation or acylation) with the different derivatization agents(BSTFA+1%TMCS:N,O-bis(trimethylsilyl)trifluoroacetamide+1%trimethylchlorosilane or PFPA:Pentafluoropropionic anhydride) separately. However, no benzoylecgonine could be detected in the samples analyzed by GC/MS. In Method C, the samples were derivatized with BSTFA:TMCS(99:1) after being extracted with the mixed mode solid phase extraction(SPE) cartridge. Benzoylecgonine could be detected in the samples analyzed by GC/MS. Polar and amphoteric substance, benzoylecgonine, could not be isolated while non-polar and basic substances, cocaine and cocaethylene, could be easily isolated from urine by LLE. It has been considered that SPE is more advantageous than LLE owing to the fact that it is to be possible one-time and simultaneous extraction of the analytes with different polarity by mixed mode SPE cartridge. It has been necessary to derivatize benzoylecgonine because of its polar structure before GC/MS analysis. BSTFA:TMCS(99:1) has been seen to be a more suitable agent than PFPA alone in the derivatization of benzoylecgonine.