The quality control of pellets homogeneity cannot be assessed by conventional techniques and near infrared-chemical imaging combined with multivariate curve resolution with alternating least squares is an attractive alternative. In this study, composition and spatial distribution of pellets components were determined after assessment of experimental parameters. The use of a 25 μm intermediate pixel size, an initial estimation matrix with instrumental signals for pure substances and individual matrices provided a model with explained variance of more than 99% and a value of 0.00263 for percentage of lack of fit. In addition, the similarity between the pure substances spectra and those recovered by the model were 0.9501 for sucrose, 0.9480 for starch, 0.9910 for ketoprofen and 0.5941 for SiO2. Chemical images were generated and show that the pellet is composed of an inert nucleus of starch and cellulose, surrounded by a ketoprofen layer. All this information was obtained quickly, in minutes, being an excellent alternative for pellets analysis.

The aim of this manuscript is to present a didactic experiment based on the combination of Near Infrared chemical imaging and Multivariate Curve Resolution for beginners, undergraduate and graduate students. In this tutorial, using MATLAB environment, the instrumental signals will be separated into two matrices, of spectral profiles and relative concentrations in the samples. Then, chemical images were generated to identify and verify the distribution of the components in the pellet samples. Chemical imaging was obtained from the mapping of predetermined area and the results for relative concentrations obtained in the ALS optimization for the analyzed area. This approach was successfully tested in chemistry undergraduate course at the Chemistry Institute of Campinas State University.

An energy dispersive X-ray fluorescence (EDXRF) analysis has been performed on Brazilian postage stamps to understand the elementary profile present in the paper, colored and postmarked areas, of stamps printed between 1850 and 1922. The EDXRF technique offered a fast, simple and nondestructive chemical analysis providing a profile of each postage stamp that provide a valuable data, such as information about raw materials employed in manufacturing process. Furthermore, we extend the methodology to detect counterfeit samples, since that some rare samples can cost fortunes, which naturally leads to cases of forgery in philately.

A fluorescência de raios X (XRF) é uma técnica bem estabelecida na caracterização de ligas metálicas e, atualmente, aparelhos portáteis começam a se tornar populares. O objetivo desse estudo foi analisar colares, brincos, pulseiras, anéis e piercings com espectrômetros de XRF portátil e de bancada, verificando se o método permite a classificação de joias com relação às exigências das normas. Além disso, comparar e checar a viabilidade de análises de campo com o equipamento portátil em apenas 5 s de irradiação. No total, 117 peças foram analisadas, ultrapassando 450 medidas. Os elementos Ni e Pb foram encontrados em uma série de amostras com concentrações superiores àquelas recomendadas, mesmo naquelas consideradas livres de Ni e Pb. Assim, foi possível determinar teores de elementos nobres e alergênicos com adequada detectabilidade, baixos desvios e boa concordância entre os equipamentos empregados, sem etapas de pré-tratamento das amostras e sem geração de resíduos.

X-ray fluorescence (XRF) is a widespread technique for alloy characterization and nowadays portable instruments are becoming popular. The objective of this study was to analyze necklaces, earrings, bracelets, rings and piercings by portable and benchtop XRF equipments, in order to verify if the presented methodology allows characterization of these objects, determining whether they meet - or not - current legislations regarding the concentrations of metals. Also to compare the equipments and check the feasibility of field measurements with portable equipments in just 5 s of analysis. In total 117 pieces were analyzed, surpassing 450 measurements. Nickel and Pb were found over the established limit in several samples, even on those attested as Ni- and Pb-free. It was possible to verify contents of noble or allergenic metals, with adequate detectability, low deviation and good agreement between both equipments employed, without sample treatment steps and without residue generation.

Compulsory in Brazil, toy certification aims to prevent possible risks in toy use. The Brazilian National Institute of Metrology (INMETRO) establishes the maximum concentration of toxic elements (TE) that may be present in toys. This study evaluates the presence of TE in different crayons, gouache and modeling clays using X-ray fluorescence. This technique is fast, has low operating cost and minimum sample pretreatment, resulting in a clean procedure without reagent consumption and waste generation. Bromine (in gouache) and Barium (in crayons) were the only potentially TE identified in the samples studied.

Recentemente, o dióxido de titânio foi classificado como potencialmente carcinogênico pela International Agency for Research on Cancer (IARC). Dióxido de titânio é um pigmento geralmente utilizado como opacificante em cremes dentais, porém sua concentração não é indicada nos rótulos dos produtos. Neste estudo, 22 amostras de cremes dentais foram calcinadas a 800 ºC e o teor de TiO2 foi determinado por fluorescência de raios X por energia dispersiva (EDXRF) através do método de parâmetros fundamentais (FP). As mesmas amostras foram irradiadas in natura por 100 s e, através da correlação dos espectros e das concentrações anteriormente determinadas, um modelo multivariado de calibração foi construído. Oito variáveis latentes descreveram o modelo de regressão de mínimos quadrados parciais (PLS) com erros médios de 9,5%, indicando que além do pico referente ao titânio, as informações do espalhamento da radiação também são importantes para minimizar os erros ao usar uma calibração univariada. A rapidez das análises, com mínimo pré-tratamento das amostras, é a grande vantagem do método, que tem frequência analítica de 24 determinações por hora.

Recently, the International Agency for Research on Cancer (IARC) has classified titanium dioxide as potentially carcinogenic. Titanium dioxide is a pigment generally used as opacifying agent in toothpastes, but there is no indication of the percentage of this oxide in these products. In this work, 22 distinct toothpaste samples were calcinated at 800 °C and TiO2 concentration was determined with energy dispersive X-Ray fluorescence (EDXRF) via fundamental parameter (FP) method. The same samples were irradiated in natura for 100 s and through the correlation of spectra and concentrations formerly determined, a multivariate calibration model was constructed. Eight latent variables described the partial least square regression (PLS) model with average errors of 9.5%, indicating that beyond the peak of titanium, the information of the X-Ray scattering irradiation is also important to minimize errors when using an univariate calibration. As a major advantage, the method allows analysis without pretreatment of the samples, with a throughput of 24 determinations per hour.

Dendrochemistry is based on the determination of elements retained in tree rings, which can be useful to characterize environmental occurrences. This work shows elemental mappings obtained by EDXRF of the cross section of a tree stem. The tree is originated from a polluted area in Campinas, São Paulo. Some profiles, as the sulfur one, show variations that can be attributed to external contributions, whereas the silicon one can be inferred to a protection defense natural mechanism. Besides being simultaneous and multielementar, the main advantages here are its performance through a non-destructive sample treatment and the ease of operation of XRF equipments.