Quantitation of cocaine on banknotes

Johnson, Amy Charlotte

Abstract

Money suspected of being involved with drug related crime can be seized by law enforcement agencies and forensically tested for traces of drug contamination. Forensic experts compare these results with background levels found on ‘normal’ banknotes, and opine as to whether the contamination indicates involvement with illicit activities. Experiments were conducted to establish the efficiency of using thermal desorption tandem mass spectrometry (TD-MS/MS) for quantitative banknote analysis, and to compare with other techniques available. Certified standards of deuterated cocaine and cocaine hydrochloride were used for instrument calibration, optimisation, or as an internal standard.

Solvent extraction from a quarter of a ‘normal’ banknote (obtained from a bank) using methanol was conducted. The extraction method involved twice washing and then a final rinse. Extraction efficiencies were calculated to be 95%, with a standard deviation of +/- 4.

Extracts were spiked with 500 ng/mL deuterated standard, and injected into the TD-MS/MS in selected reaction monitoring mode. Isotope dilution using known amounts of cocaine hydrochloride and deuterated cocaine was used to establish a response factor. The peak areas of the deuterated internal standard were compared with the cocaine extracts, and the response factor was used to calculate the amount of cocaine. Average amounts of 4.6 µg and 7.7 µg were detected on individual banknotes, and batch tests of banknotes respectively.

GC/MS gave initial results of approximately 20 µg cocaine per banknote, following drying and reconstitution of the extract. Further research of internal standards and response factor is needed. Simple filtration clean up, or drying under nitrogen and reconstituting in mobile phase was applied for HPLC, however, tests proved inconclusive with further work required into clean up steps. Fluorescence work identified self-quenching and potential interferents from banknotes.

Overall the TD-MS/MS work proved successful and found that amounts of cocaine on banknotes can be established using isotope dilution, with approximately 10% error. GC/MS could be a useful comparative tool.

• Thesis Type: Thesis
• Publicly Available Date: Jun 7, 2019
• Keywords: banknotes, sterling, cocaine, drugs, quantitation, MS/MS, thermal desoprtion, GC/MS
• Public URL: https://uwe-repository.worktribe.com/output/880249
• Additional Information: Corporate Creators : Mass Spec Analytical Ltd.
• Award Date: Oct 1, 2017