Desenvolvimento de método para identificação de droga inalante em perícia criminal por espectroscopia NIR e quimiometria

Abstract

A homemade mixture of organic solvents, known in Brazil as “loló”, stands out among the most misused inhalant substances in this country. Traditionally, it was composed of ether and chloroform, however, reports in the literature and practice of criminal expertise reveal changes in the composition profile of this drug, impacting the efficiency of preliminary tests used for immediate detection of illicit substances in order to produce the necessary evidence to support police actions, such as arrests. Considering the diversity of volatile substances with potential misuse and the limited detection of preliminary tests routinely used by forensic laboratories, this study aimed to employ NIR spectroscopy associated with chemometric models to detect organic solvents in samples of “loló” as alternative to the methods commonly used in forensic laboratories. A survey was carried out to know the composition profile of the seized samples in the geographic region studied (State of Paraíba) in order to direct the design of synthetic mixtures used in the construction of classification models. In addition to synthetic samples, real samples duly characterized by GC-MS were used to compose sample sets. Then, an analysis protocol was developed, based on SIMCA models, to detect the prevalent solvents in the regional composition profile obtained (dichloromethane, trichlorethylene and chloroform). The proposed analysis protocol obtained an 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 for detecting halogenated hydrocarbons do not detect dichloromethane, the most prevalent solvent among those studied, the proposed method proved to be technically and economically feasible in preliminary tests for seized samples suspected to contains these solvents.