Blotter papers seizures containing synthetic drugs have intensified over the last decades. These drugs were originally conceived as “legal” alternatives to traditional illicit drugs, designed to mimic their effects and circumvent control agencies. Reference methods for determining these substances on blotter papers are based on chromatographic techniques using mass spectrometry detection. However, these procedures are destructive, expensive, and time consuming. Some compounds are also thermolabile and not suitable for regular gas chromatography analyses. In this paper, two multivariate models were presented and incorporated in the routine of a forensic laboratory as a screening method. They were developed and validated using a representative dataset of 158 seizures analyzed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and a partial least squares-discriminant analysis (PLS-DA) model. The first model (model A) discriminates between samples with and without different types of drugs, and the second one (model B) discriminates between samples containing NBOMe and NBOH, two N-benzyl 2,5-dimethoxy substituted phenethylamine commonly incorporated into blotter papers. The proposed method is fast, non-destructive, and requires no sample preparation. Both models showed reliable results (misidentification errors < 10%), presented good results in a real forensic laboratory routine, and can be updated to include new drugs.

Supervising wood exploitation can be very challenging due to the existence of many similar species and the reduced number of wood identification experts to meet the demand. There is evidence that valuable endangered wood species are being smuggled disguised as other species. Near infrared spectroscopy (NIRS) and chemometrics has been successfully used to discriminate between Amazonian wood species using high resolution instruments. In this study, a handheld spectrometer was evaluated for the discrimination of six visually similar tropical wood species using PLS-DA. Woods of mahogany (Swietenia macrophylla) and cedar (Cedrela odorata), both high value tropical timber species included in Appendixes II and III of the CITES, respectively; crabwood (Carapa guianensis); cedrinho (Erisma uncinatum); curupixá (Micropholis melinoniana); and jatobá (Hymenea coubaril). The data for model development and validation take into account both laboratory and field measurements. Outlier exclusion was performed based on Hotelling T2, residuals Q and errors in the estimated class values. The efficiency rates were higher than 90% for all species, showing that the handheld NIR combined with PLS-DA succeeded in discriminate between these species. These results stimulate the application of handheld NIR spectrometers in the supervision of wood exploitation, which can contribute to the species preservation.

This work describes a new procedure for classification of mineral waters based on digital images acquired by smartphones. Commercial waters from eight mineral springs plus distilled water and tap water were combined with eriochrome T black or murexide and transferred to a cuvette, which was positioned into a light controlled chamber. RGB (Red, Blue and Green) measurements of cuvette images were acquired in real time, using a free smartphone app, and employed as variables for the exploratory analysis. 2D data dispersion along component B for murexide (x axis) and component R for eriochrome T black (y axis) provides the clear visualization of clusters using the raw variables. Hierarchical cluster analysis (HCA) applied to this data confirmed the efficient discrimination of samples providing the characterization of nine clusters for the ten classes of water investigated. The classification of samples based on a k-nearest neighbors (k-NN) modelled to the efficiency rate of 100% for 8 classes and of 94.4% and 50% for the remaining classes, respectively, indicating the adequate performance of the proposed strategy. Considering the facilities to acquire the data, such as low cost instrumentation and reagents, and the rapidity of the procedures, this alternative may be applied for verification of commercial water adulteration.

The determinations of cellulose and lignin are important in wood analysis from both perspectives: chemistry composition, commercial and industrial application of woods. In this context, Raman image spectroscopy was applied in the determination of cellulose and lignin distribution in wood surfaces of Swietenia macrophylla King (Mahogany) and Eucalyptus hybrid (E. urophylla × E. camaldulensis). The relative concentration maps were obtained by applying a multivariate curve resolution procedure. The estimated Raman spectra for cellulose and lignin agrees with the ones available in the literature. The cellulose concentration maps showed similar variations for both studied species with an average value of nearly 85% as obtained by the reference method. The lignin concentration maps were somewhat different. The Eucalyptus hybrid presents a broader distribution (20 to 45%) while for Mahogany it is nearly constant, around 25%, with localized regions presenting contents of 45 to 65% of lignin. The reference method showed that the mean lignin content of both species is 27%. The cellulose and lignin concentration maps agree with the biological functions of the anatomic structures observed in the images.

A determinação do teor de cocaína em amostras de drogas consiste em uma importante tarefa em órgãos como a Polícia Federal Brasileira (BFP). Nesse sentido, este trabalho propõe apresentar um método baseado em espectros de infravermelho obtidos por refletância total atenuada (ATR) e regressão por mínimos quadrados parciais (PLSR) para quantificar cloridrato de cocaína em amostras de drogas. O método foi desenvolvido e validado com 275 amostras reais de drogas apreendidas pela BFP em todo o Brasil. A determinação foi realizada no intervalo de 35 a 99% (m/m) de cocaína nas amostras. Os resultados indicaram que o método é capaz de analisar diretamente amostras de drogas contendo cocaína na forma de cloridrato sem necessidade de qualquer preparo de amostra com erros médios de aproximadamente 3,00%, precisão de 1,50% (m/m) e concentração mínima detectável de 13% (m/m).

The determination of cocaine in drug samples is an important task for law enforcement agencies such as the Brazilian Federal Police (BFP). In this sense, this paper proposes a method based on infrared spectra obtained by attenuated total reflectance (ATR) and partial least squares regression (PLSR) to quantify cocaine hydrochloride in drug samples. The method was developed and validated with 275 actual samples of drugs seized by the BFP. The determination was performed between 35 to 99% (m/m) of cocaine in the drug samples. Results indicate that the method is able to directly analyze drug samples containing cocaine in its hydrochloride form without any sample preparation with average prediction errors of 3.00% (m/m), 1.50% (m/m) precision and 13% (m/m) of minimum detectable concentration.

A análise de tintas é realizada para verificar a ocorrência de falsificações em documentos. Nesse aspecto, métodos espectroscópicos são atrativos, pois preservam a integridade do documento. Neste trabalho, é proposto um método para a discriminação de tintas de canetas pretas entre tipos, marcas e modelos para a aplicação em documentos. Espectros de reflectância na região visível foram obtidos através do equipamento comparador espectral de vídeo VSC®6000 e da análise discriminante por mínimos quadrados parciais (PLS-DA). O método foi validado com dados independentes e um teste cego. O viés presente nos resultados foi corrigido para a detecção das amostras anômalas. Os modelos PLS-DA apresentaram baixos erros médios quadráticos de previsão (RMSEP) e permitiram a discriminação de todas as tintas de forma rápida, não destrutiva e eficiente. O método se mostrou exato e robusto com respeito a escrita de diferentes indivíduos e capaz de identificar o tipo, a marca e o modelo de caneta em um caso forense.

The analysis of inks is performed to verify the occurrence of forgery in documents. Spectroscopic methods are attractive techniques for use in forensic document analysis as they, in most instances, preserve the integrity of the document. In this work, it is proposed a discrimination method of black pen inks of different types, brands and models for application in cursive handwriting. The visible reflectance spectra was obtained by the video spectral comparator VSC®6000 and discrimination analysis performed by partial least squares (PLS-DA). The method was validated with an independent test set and with a blind test. The bias in the results was corrected for the outlier identification. The PLS-DA models presented low root mean squared error of predictions (RMSEPs) and allowed a fast, non-destructive and an efficient discrimination of all pen inks evaluated. The method has proved to be accurate and robust regarding the handwriting of different individuals and capable of identifying the pen type, brand and pen model in a forensic case.

The validation of an analytical procedure must be certified through the determination of parameters known as figures of merit. For first order data, the acuracy, precision, robustness and bias is similar to the methods of univariate calibration. Linearity, sensitivity, signal to noise ratio, adjustment, selectivity and confidence intervals need different approaches, specific for multivariate data. Selectivity and signal to noise ratio are more critical and they only can be estimated by means of the calculation of the net analyte signal. In second order calibration, some differentes approaches are necessary due to data structure.

Os teores de sólidos solúveis (BRIX), açúcares polarizáveis (POL) e açúcares redutores (RS) em caldo de cana foram determinados utilizando espectroscopia na região do infravermelho próximo (NIR) e calibração multivariada, a qual foi validada pelo cálculo das figuras de mérito. Devido à heterogeneidade das amostras, foi necessário, como primeira etapa do trabalho, a otimização dos conjutos de calibração e validação através da eliminação das amostras anômalas (outliers). As figuras de mérito como: sensibilidade, sensibilidade analítica, seletividade, limites de confiança, precisão (média, repetibilidade), exatidão e razão sinal-ruído foram calculadas. Resultados viáveis foram obtidos para BRIX e POL apresentando resultados de RMSEP de 0,28 e 0,42% de caldo, respectivamente. Os coeficientes de correlação para ambos os parâmetros foram de 0,99. Estes resultados indicam que os modelos desenvolvidos para BRIX e POL podem ser seguramente utilizados como uma alternativa em relação ao método padrão utilizado na indústria alcooleira.

The determination of soluble solids (BRIX), polarizable sugars (POL) and reducing sugars (RS) sugar cane juice by using near infrared spectroscopy (NIR) and multivariate calibration was developed and validated by calculation of figures of merit. Due to the heterogeneity of the samples, first it was necessary to optimize the calibration set by outlier elimination. The figures of merit such as: sensitivity, analytical sensitivity, selectivity, confidence limit, precision (mean, repeatability), accuracy and signal-to-noise ratio were calculated. Feasible results were obtained for BRIX and POL with RMSEP values of 0.28 and 0.42% of juice and precision of 0.02 and 0.08% of juice, respectively. For both BRIX and POL goodness of fit showed correlation coefficients of 0.99. These results indicate that the models developed for BRIX and POL can be used as an alternative to standard procedures in the sugar cane industry.