title: Discrimination and quantification of cocaine and adulterants in seized drug samples by infrared spectroscopy and PLSR.
abstract: Middle infrared spectroscopy and multivariate analysis have been applied for the development of methods to perform both quantitative and qualitative analysis of real drug samples seized by the Brazilian Police Federal (BPF). Currently, quantification of cocaine and determination of adulterants in seizures is performed using gas chromatography with flame ionization detection. However, this technique requires a relatively complex sample preparation, higher time of analysis, the destruction of sample and a high cost. In this context, this paper presents a simpler method to quantify cocaine and its major adulterants in seized materials. Out of 375 seizures, taken within a time frame of 2009-2013. A total of 1085 samples were analyzed of which 500 were selected for the calibration set and 585 for the validation set. Cocaine concentration in seized samples was determined by using middle infrared spectroscopy and partial least squares regression (PLSR), obtaining an average prediction error of 3.0% (w/w), precision of 2.0 and 11.8% (w/w) of minimum detectable cocaine concentration in a range varying from 24.2 to 99.9% (w/w). Results indicate that the developed method is able to discriminate between cocaine hydrochloride and free base samples, to quantify cocaine content as well as to estimate the concentration of main adulterants phenacetin, benzocaine, caffeine, lidocaine and aminopyrine.
authors.affiliation: Institute of Chemistry, University of Brasília, PO Box 4478, 70904-970 Brasília, DF, Brazil.
authors.forename: Tatiane S
authors.initials: TS
authors.lastname: Grobério
authors.affiliation: National Institute of Criminalistics, Brazilian Federal Police, SAIS Quadra 07 Lote 23, 70610-200, Brasília, DF, Brazil.
authors.forename: Jorge J
authors.initials: JJ
authors.lastname: Zacca
authors.affiliation: National Institute of Criminalistics, Brazilian Federal Police, SAIS Quadra 07 Lote 23, 70610-200, Brasília, DF, Brazil.
authors.forename: Élvio D
authors.initials: ÉD
authors.lastname: Botelho
authors.affiliation: National Institute of Criminalistics, Brazilian Federal Police, SAIS Quadra 07 Lote 23, 70610-200, Brasília, DF, Brazil.
authors.forename: Marcio
authors.initials: M
authors.lastname: Talhavini
authors.affiliation: Institute of Chemistry, University of Brasília, PO Box 4478, 70904-970 Brasília, DF, Brazil. Electronic address: jez@unb.br.
authors.forename: Jez W B
authors.initials: JWB
authors.lastname: Braga
mesh_terms: D001938:Brazil; D003042:Cocaine / Q000032:analysis*; D004340:Drug Contamination; D064423:Drug Trafficking; D006801:Humans; D013287:Illicit Drugs / Q000737:chemistry*; D016018:Least-Squares Analysis; D013055:Spectrophotometry, Infrared
chemical_list: D013287:Illicit Drugs; D003042:Cocaine
keywords: Characterization; Chemometrics; Direct analysis; Multivariate analysis; Quantification