A new method to identify the authenticity of Brazilian banknotes (R$) is proposed using digital image analysis by a smartphone application, Photometrix®, associated with chemometric tools. Authentic banknotes (n = 4) obtained in local bank and falsified (n = 12) by the author himself by means of three printers (laser-Deskjet®, wax-Color Qube® and inkjet-Deskjet®) were used for the development of the methodology. An experimental planning was performed to evaluate the authenticity of the banknotes determining: the best region (holographic band, tactile region in the lower left and right upper number, effigy microimpressions, lower number left, animal figure, watermark and puzzle); Region of Interest (ROI) (16x16; 32x32 and 64x64 pixels), focal length (8, 12, 15 and 20 cm) and variation of the smartphone (Motorola G5 Plus, Samsung S7 and LG K10). The best regions chosen were effigy microimpressions and round the animal. Promising results were obtained from ROI 16x16 pixels with focal length fixed at 10 cm. Thus, the application presents promising features for analyzing the authenticity of banknotes by digital images making it fast, non-destructive, portable, with low cost, and can be accessed by all society.

The use of insects to identify drugs in a cadaver has often been explored in the field of entomotoxicology. There are accurate methods; however, they require a high cost and are very time-consuming. The objective of this study was to develop two methods based on differential pulse voltammetry (DPV) and fluorescence excitation-emission matrix (EEM) spectroscopy to classify necrophagous larvae (Chrysomya megacephala, C. albiceps, Lucilia sp. and Cochliomyia macellaria) containing flunitrazepam. The voltammograms of larval extract samples were analyzed by principal component analysis (PCA), successive projection algorithm (SPA) and genetic algorithm (GA): linear and quadratic discriminant analysis (LDA and QDA). The EEM fluorescence data from larval extract samples were analyzed by 2D and parallel factor analysis (PARAFAC) with LDA. These results suggest that DPV and EEM combined with chemometrics can be used as tools for the classification of flunitrazepam in fly larvae presenting innovative applications.

Mass spectrometry (MS) is a powerful technique that can provide the biochemical signature of a wide range of biological materials such as cells and biofluids. However, MS data usually has a large range of variables which may lead to difficulties in discriminatory analysis and may require high computational cost. In this paper, principal component analysis with linear discriminant analysis (PCA-LDA) and quadratic discriminant analysis (PCA-QDA) were applied for discrimination between healthy control and cancer samples (ovarian and prostate cancer) based on MS data sets. In addition, an identification of prostate cancer subtypes was performed. The results obtained herein were very satisfactory, especially for PCA-QDA. Selectivity and specificity were found in a range of 90-100%, being equal or superior to support vector machines (SVM)-based algorithms. These techniques provided reliable identification of cancer samples which may lead to fast and less-invasive clinical procedures.

The use of digital image analysis as an analytical tool is a reality nowadays, and the use of smartphones stands out due to its high accessibility and practicality. Ascorbic acid (AA) is a natural and essential vitamin available as a supplement as a result of its use in preventing and treating several pathologies. This paper reports a simple, fast and low cost method using smartphone image analysis for quantification of AA based on its interfering effect in the enzymatic colorimetric detection of glucose. Commercial vitamin C tablets were used as prediction set for AA quantification, showing very satisfactory results (relative errors < 4%), where no statistical difference at a 95% confidence level was observed between the AA content estimated by the imaging method and the labeled reference values. As advantages, this method does not use expensive reagents neither laborious procedures to carry out the analysis.

This paper presents a low-cost reflectometer for selective detection of Cu2+. The reflectometer is based on an emission light source using five light-emitting diodes at different wavelengths and a detector using a webcam. The samples were prepared using a filter paper-based colorimetric sensor with ascorbic acid-based quinoxaline derivative. Video analysis using gray color intensity was used to perform both copper ion screening (Cu2+, Pb2+, Cr+3, Ni2+, Fe2+, Sn2+, Mg2+, Cd2+, Ag+ and Co2+) and quantification of Cu2+ in spiked samples. In addition, a multivariate validation was performed. The system proved to be selective to Cu2+ among the screened ions, and its quantification was performed using partial least square regressions. Good linearity (R2 = 0.979, coefficient of determination), low root-mean-square error of prediction (RMSEP = 5.20 × 10-3 mol L-1) and high recovery (93.39-128.64%) were achieved. This method has potential to be employed for rapid and selective determination of Cu2+ in water using low-cost instrumentation.

The aim of this study was to quantitatively determine the olanzapine in a pharmaceutical formulation for assessing the potentiality of near infrared spectroscopy (NIR) combined with partial least squares (PLS) regression. The method was developed with samples based on a commercial formulation containing olanzapine and seven excipients. Laboratory and commercial samples (n = 27 and 18, respectively) were used by defining the calibration and prediction sets. The method was validated in the range from 1.0 to 12.5 of olanzapine per 100 mg of powder (average mass 210 mg), by accuracy, precision, linearity, analytical sensitivity, limit of detection and quantification. The multivariate model developed for olanzapine was based on PLS and the determination coefficient (rc and rp), with the root mean square error of calibration and prediction being 0.95, 0.93, 3.2 × 10-3 and 4.0 × 10-3% m/m, respectively. The proposed NIR method is an effective alternative for quantification of olanzapine in the pharmaceutical industry.

This paper describes the use of digital imaging acquired from a conventional desktop scanner for characterization of newly synthesized amino-nitroquinoxaline dyes. The synthetic protocol was based on reactions of building block 2,3-dichloro-6,7-dinitroquinoxaline with aliphatic amines and experiments based on image analysis were carried out with compounds in solution (96-microwell plates) and/or adsorbed on silica (thin-layer chromatography (TLC) plates). Three main goals were achieved: firstly, compounds 2-chloro-6,7-dinitro-3-pyrrolidinoquinoxaline and 6,7-dinitro-2,3-dipyrrolidinoquinoxaline had their concentration predicted in dimethyl sulfoxide (DMSO) solution, as a mixture. Secondly, TLC studies were performed to build a kinetic profile in attempt to monitor reaction involving conversion of 2-chloro-6,7-dinitro-3-pyrrolidinoquinoxaline into 6,7-dinitro-2,3-dipyrrolidinoquinoxaline. Lastly, image analysis and UV-Vis spectroscopy were applied to study the interaction of 2,3-di-n-butylamino-6,7-dinitroquinoxaline with hydroxide anion in DMSO. These approaches based on digital image characterization were successfully implemented in qualitative and quantitative analysis of organic dyes.

Bioorganic and biological chemistry have been found to be highly motivating to undergraduate students and in this context, biochemical blood parameter analysis emerges as highly attractive content. In this proposal, several aspects related to analyses of glucose, cholesterol and triglycerides using the enzymatic colorimetric method were involved, and the findings have at least two relevant implications: i) introducing students to connections between organic chemistry and biology based on enzymatic processes, including reactivity and mechanistic aspects; ii) performing a micro scale bioassay analysis. The proposal requires two theoretical classes (2 h per class) and one practical class (4 h).

Uma das chaves para manter a melhoria da alta qualidade de fabricação está no uso de cartas de controle. Neste trabalho, cartas de controle multivariada baseadas nos escores da componente principal mais significativa e no sinal analítico líquido foram desenvolvidas para monitoramento simultâneo da qualidade de dois princípios ativos (isoniazida e rifampicina) numa formulação farmacêutica (amostras produzidas no laboratório e na produção) empregando um espectrômetro portátil na região do infravermelho próximo. Os limites previstos em ambas as cartas multivariadas foram calculados a partir das especificações de qualidade da formulação farmacêutica (± 5% do valor nominal para cada princípio ativo). O uso das cartas de controle multivariadas forneceu uma simples e poderosa ferramenta para avaliar a formulação farmacêutica aliada a espectroscopia no infravermelho próximo. O procedimento é rápido e flexível para o monitoramento da produção desta formulação farmacêutica produzida na UFRN/Brasil, com o objetivo de introduzir a tecnologia analítica de processos ao tratamento de tuberculose pulmonar.

One of the keys to maintain high manufacturing quality improvement is the use of control charts. In this work, multivariate control charts based on significant principal component (PC) scores and net analytical signal (NAS) were developed to simultaneously monitor the quality of two active pharmaceutical ingredients (API) (isoniazid and rifampicin) in pharmaceutical formulation (laboratory samples and production samples) using a portable near infrared spectrometer. The limits for both multivariate charts were estimated using the quality specifications from the pharmaceutical formulation (± 5% of the nominal content of each API). The use of these multivariate control charts has provided a simple and powerful tool to evaluate the content of pharmaceutical formulations based on isoniazid and rifampicin capsules combined with near infrared spectroscopy. The procedure is rapid and adjustable for monitoring the production of the pharmaceutical preparations produced at UFRN/Brazil toward the process analytical technology (PAT) for the treatment of pulmonary tuberculosis.

Analytical Chemistry books lack a clear link between thermodynamic and equilibrium approaches involving acids and bases. In this work, theoretical calculations were performed to search for these relations. An excellent relationship was found between difference in Gibbs free energy, ∆G of acid dissociation reaction and ∆G of hydrolysis reaction of the corresponding conjugate base. A relationship between ∆G of hydrolysis reaction of conjugate acids and their corresponding atomic radius was also identified, showing that stability plays an important role in hydrolysis reactions. Finally, the importance of solvation in acid/base behavior was demonstrated when comparing the corresponding theoretical and experimental ∆G´s.

O objetivo deste estudo foi avaliar a potencialidade da espectroscopia no infravermelho próximo (NIRS) como um método rápido e não destrutivo para determinação do teor de sólidos solúveis (SSC) e pH em ameixas intactas. Amostras de ameixa com teores de sólidos solúveis variando de 5,7 a 15% e pH entre 2,72 e 3,84 foram adquiridas em supermercados em Natal (Rio Grande do Norte, Brasil) e espectros NIR foram coletados no intervalo de 714-2500 nm. Uma comparação de algumas técnicas de calibração multivariada com relação ao preprocessamento dos dados e algoritmos de seleção de variáveis, tais como mínimos quadrados parciais por intervalos (iPLS), algoritmo genético (GA), algoritmo das projeções sucessivas (APS) e seleção de preditores ordenados (OPS), foi realizada. Modelos de validação para SSC e pH tiveram um coeficiente de correlação (R²) de 0,95 e 0,90, com erro quadrático médio de previsão (RMSEP) de 0,45 e 0,07, respectivamente. A partir desses resultados, conclui-se que a espectroscopia NIR pode ser usada como uma técnica não destrutiva para determinação de SSC e pH em ameixas.

The aim of this study was to evaluate the potential of near-infrared reflectance spectroscopy (NIRS) as a rapid and nondestructive method to determine the soluble solid content (SSC) and pH of intact plums. Samples of plum with total solid contents ranging from 5.7 to 15% and pH from 2.72 to 3.84 were collected from supermarkets in Natal (Rio Grande do Norte, Brazil) and NIR spectra were acquired in the 714-2500 nm range. A comparison of some multivariate calibration techniques with respect to several pre-processing data and variable selection algorithms, such as interval partial least squares (iPLS), genetic algorithm (GA), successive projection algorithm (SPA) and ordered predictor selection (OPS), was performed. Validation models for SSC and pH had a coefficient of correlation (R²) of 0.95 and 0.90, as well as a root mean square error of prediction (RMSEP) of 0.45 and 0.07, respectively. From these results, it can be concluded that NIR spectroscopy can be used as a nondestructive technique for determining SSC and pH in plums.

Optical chemical sensors with detection in the near and mid infrared region are reviewed. Fundamental concepts of infrared spectroscopy and optical chemical sensors are briefly described, before presenting some aspects on optical chemical sensors, such as synthesis of NIR and IR reagents, preparation of new materials as well as application in determinations of species of biological, industrial and environmental importance.

Diffuse reflectance near-infrared (DR-NIR) spectroscopy associated with partial least squares (PLS) multivariate calibration is proposed for a direct, non-destructive, determination of total nitrogen in wheat leaves. The procedure was developed for an Analytical Instrumental Analysis course, carried out at the Institute of Chemistry of the State University of Campinas. The DR-NIR results are in good agreement with those obtained by the Kjeldhal standard procedure, with a relative error of less than ± 3% and the method may be used for teaching purposes as well as for routine analysis.