Raman Spectroscopy for the in Situ Identification of Cocaine and Selected Adulterants

Abstract

We demonstrate the in situ identification of crack cocaine and cocaine·HCl by using a fiber-optic Raman probe and a portable Raman spectrograph. The Raman spectrum of freebase cocaine (crack) is obtained in just seconds without any sample preparation, and differs significantly from that of cocaine·HCl. We also show that the Raman spectra of these drugs are easily distinguishable from common cutting agents and impurities such as benzocaine and lidocaine. Another advantage of using Raman spectroscopy is that the drugs can be identified while contained in transparent containers, such as clear plastic evidence containers that are used to store drug evidence and to maintain chain of custody. We also demonstrate the in situ Raman identification of drugs separated by thin-layer chromatography. We discuss the utility of surface-enhanced Raman spectroscopy (SERS) in toxicological drug screening and present preliminary SERS data for cocaine in solution using colloidal silver. We believe this to be the first published SERS spectrum of freebase cocaine.