Cocaine and adulterants analysis in seized drug samples by infrared spectroscopy and MCR-ALS.

Cocaine use has been reported for more than 2500 years, but along this period of time its damage to society in general became evident. Nowadays, cocaine is classified as an illicit drug and studies which give support to drug enforcement institutions, particularly in the area of police intelligence, are very relevant. Often, trafficked cocaine is not traded in its pure form, but mixed with adulterants and diluents. In the analysis of seized samples, the reference method is based on gas chromatography, however the interest in the use of vibrational spectroscopy has increased. This work aims at developing a method for determination of the concentrations of cocaine, adulterants and diluents in cocaine samples employing Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) associated with Multivariate Curve Resolution with Alternating Least-Squares (MCR-ALS). A total of 6 adulterants, 3 diluents, 2 forms of cocaine (base and hydrochloride) were determined and the method developed based on 55 synthetic mixtures prepared according to a mixture design and 20 seized samples. For validation purposes 708 seized samples and 9 synthetic mixtures were analyzed. The results proved to be satisfactory, showing that the proposed method has a great potential in the classification of the chemical form of cocaine, identification of adulterants, diluents and cocaine in seized samples, as well as providing an estimate for their concentration.

Discrimination and quantification of cocaine and adulterants in seized drug samples by infrared spectroscopy and PLSR.

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.

Correlation of cocaine hydrochloride samples seized in Brazil based on determination of residual solvents: an innovative chemometric method for determination of linkage thresholds.

Cocaine sample correlation provides important information in the identification of traffic networks. However, available methods for estimating if samples are linked or not require the use of previous police investigation and forensic expert knowledge regarding the number of classes and provide thresholds that are both static and data set specific. In this paper, a novel unsupervised linkage threshold method (ULT) based on chemometric analysis is described and applied to the analysis of headspace gas chromatography mass spectrometry (HS-GC/MS) data of more than 250 real cocaine hydrochloride samples seized by Brazilian Federal Police. The method is capable of establishing linkage thresholds that do not require any prior information about the number of classes or distribution of the samples and can be dynamically updated as the data set changes. It is envisaged that the ULT method may also be applied to other forensic expertise areas where limited population knowledge is available and data sets are continually modified with the inflow of new information.

Demystifying "oxi" cocaine: Chemical profiling analysis of a "new Brazilian drug" from Acre State.

Recent information from various sources suggests that a new illicit drug, called "oxi", is being spread across Brazil. It would be used in the smoked form and it would look like to crack cocaine: usually small yellowish or light brown stones. As fully released in the media, "oxi" would differ from crack cocaine in the sense that crack would contain carbonate or bicarbonate salts whereas "oxi" would include the addition of calcium oxide and kerosene (or gasoline). In this context, this work presents a chemical profiling comparative study between "oxi" street samples seized by the Civil Police of the State of Acre (CP/AC) and samples associated with both international and interstate drug trafficking seized by the Brazilian Federal Police in Acre (FP/AC). The outcome of this work assisted Brazilian authorities to stop inaccurate and alarmist releases on this issue. It may be of good use by the forensic community in order to better understand matters in their efforts to guide local law enforcement agencies in case such claims reach the international illicit market.