Determination of cocaine contamination on banknotes using tandem mass spectrometry and pattern recognition

Analytica Chimica Acta (Impact Factor: 4.52). 02/2006; 559(1):54-63. DOI: 10.1016/j.aca.2005.11.082

ABSTRACT Tandem mass spectrometry is used to monitor the contamination of banknotes by cocaine. By introducing a series of banknotes into an instrument a distribution of contamination can be obtained. The distribution of samples arising from defendants where the banknotes have been in close proximity to cocaine should differ from the distribution from the general background population. Peak picking and integration is used to produce a series of intensity readings for a batch of banknotes. By visually inspecting these distribution, and applying a variety of chemometric methods (principal components analysis, cluster analysis and class modelling via Mahalanobis distance) it is possible to discriminate effectively between the two classes of distribution (7157 background notes and 4826 case notes alleged to be from drug dealers). By calculating the Mahalonobis distance over 100 bootstrap iterations, background samples were correctly classified 96.48% of the time, while case samples were correctly classified 89.37% of the time.

1 Bookmark
  • [Show abstract] [Hide abstract]
    ABSTRACT: A gas chromatography-differential mobility spectrometer (GC-DMS) involves a portable and selective mass analyzer that may be applied to chemical detection in the field. Existing approaches examine whole profiles and do not attempt to resolve peaks. A new approach for peak detection in the 2D GC-DMS chromatograms is reported. This method is demonstrated on three case studies: a simulated case study; a case study of headspace gas analysis of Mycobacterium tuberculosis (MTb) cultures consisting of three matching GC-DMS and GC-MS chromatograms; a case study consisting of 41 GC-DMS chromatograms of headspace gas analysis of MTb culture and media.
    Analytical Chemistry 03/2011; · 5.83 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A cocaine-specific aptamer was used as a receptor molecule in a microcantilever-based surface stress sensor for detection of cocaine molecules. An interferometric technique that relies on measuring differential displacement between two microcantilevers (a sensing/reference pair) was utilized to measure the cocaine/aptamer binding induced surface stress changes. Sensing experiments were performed for different concentrations of cocaine from 25 to 500 μM in order to determine the sensor response as a function of cocaine concentration. In the lower concentration range from 25 to 100 μM, surface stress values increased proportionally to coverage of aptamer/cocaine complexes from 11 to 26 mN/m. However, as the cocaine concentration was increased beyond 100 μM, the surface stress values demonstrated a weaker dependence on the affinity complex surface coverage. On the basis of a sensitivity of 3 mN/m for the surface stress measurement, the lowest detectable threshold for the cocaine concentration is estimated to be 5 μM. Sensing cantilevers could be regenerated and reused because of reversible thermal denaturation of aptamer.
    Langmuir 08/2011; 27(23):14696-702. · 4.38 Impact Factor