Analysis of street cocaine samples in nasal fluid by Raman spectroscopy

The principal objective of this work was to demonstrate the capability of Raman spectroscopy to detectsmall amounts of cocaine in nasal fluid, and to identify the main drug and the most widely used cuttingagents. Initially, standard samples were analysed and sampling conditions were studied by comparingdifferent swabs used for the sample collection. Once the most appropriate swab was selected, whichpermitted a relatively simple detection of the standard cocaine hydrochloride, qualitative analyses of realsamples were carried out. Three street cocaine samples were analysed, and the presence of cuttingsubstances was highlighted by the appearance of different bands not corresponding to the ones of thestandard cocaine. To identify the substances present in each sample, the spectra of the street cocainesamples were collected and compared with a digital library created on purpose with the spectra of themost common cutting agents. In this case, correlation coefficients permitted to recognize the most importantsubstances presumably present in the samples, and gave an estimation of the purity of the cocaine.However, when nasal fluid was present, its strong signal could overlap or interfere with thesmaller signal of the cutting substances, hindering their identification