Applications of NIR spectroscopy and chemometrics to illicit drug analysis: An example from inhalant drug screening tests.

The "loló" stands out among the most used inhalant drugs in Brazil. This drug is a non-specific blend of organic solvents, traditionally composed of ether and chloroform. Reports in the literature and forensic practice have revealed changes in the composition profile of this drug, based on availability of acquisition. This diversity has an effect on the efficiency of the preliminary tests used to detect illicit substances in situations that require rapid response time from the criminal investigations, such as arrests in the act. Considering the diversity of volatile substances with potential use as inhalant drugs and the limited detection abilities of preliminary exams routinely used by forensic laboratories, this present work applied NIR spectroscopy associated with chemometric models to detect the presence of organic solvents in samples of "loló". Initially, the chemical profile of the seized samples was surveyed in the geographic region of study (Paraiba State, Brazilian northeast), and from the observation of the prevalent substances, classification models were produced using samples made in the laboratory and samples from real apprehensions. Then, an analysis protocol was developed, based on SIMCA models, to detect the predominant solvents in the regional composition profile (dichloromethane, trichloroethene and chloroform). The proposed analysis protocol obtained an overall accuracy of 94.7% in detecting halogenated hydrocarbons in suspect samples and 100% accuracy in characterizing the composition of samples composed exclusively of the studied halogenated hydrocarbons and their binary mixtures. Considering that the colorimetric tests used in the routine of forensic laboratories do not detect many components, the proposed method was technically and economically viable in preliminary tests for samples seized as suspicious of being "loló".