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.

Em análise forense, uma pequena quantidade de um determinado material (cabelo, fibras, solo, vidro, pintura, entre outros) pode ser fundamental para elucidar a sequência de eventos em uma cena de crime ou para estabelecer a relação entre sujeitos e fatos. Existem vários exemplos de cosméticos usados como provas forenses, tais como batons e esmaltes de unhas. A composição desses esmaltes pode variar de acordo com a marca, cor e finalidade do produto. Neste trabalho, a classificação de esmaltes de unha brasileiros de acordo com a marca foi avaliada usando um espectrômetro portátil de fluorescência de raios X por energia dispersiva (EDXRF) e análise de componentes principais (PCA). A classificação não supervisionada das cinco marcas indica que a metodologia proposta pode ser uma alternativa rápida, de baixo custo e compatível com a química verde para discriminar marcas e outras características relacionadas a uma amostra de esmalte de unha, como possível evidência em cenas de crime.

In forensic analysis, a small quantity of a particular material (hairs, fibers, soils, glasses, paints, among others) can be important to elucidate the sequence of events in a crime scene or to establish the relationship among subjects and facts. There are several examples of cosmetics used as forensic evidences, such as lipsticks and nail polishes. The composition of nail polishes varies according to brand, color and purpose of the product. In this work, the separation of Brazilian nail polishes according to their brand was evaluated using a portable energy dispersive X-ray fluorescence spectrometer (EDXRF) and principal component analysis (PCA). The nonsupervised classification of five brands indicates that the proposed methodology may be a quick, low cost and green alternative to discriminate brands and other characteristics related to a nail polish sample, as possible evidence in crime scenes.

This work describes three C8-stationary phases for high performance liquid chromatography based on silica metallized with ZrO2, TiO2 or Al2O3 layers, having poly(methyloctylsiloxane) immobilized onto their surfaces. The stationary phases were characterized using XRF, XAS, FTIR, SEM and elemental analysis to determine the physical characteristics of the oxide and polysiloxane layers formed on the surfaces and chromatographically to evaluate the separation parameters. The results show the changes on the silica surface and allowed proposing a structure for the oxide layer, being observed tetrahedral and octahedral structures, what is completely new in the literature. The formation of a homogeneous layer of metallic oxide (TiO2 and ZrO2) was observed on the silica. The C8-titanized and C8-aluminized stationary phases presented good chromatographic performances, with good values of asymmetry and efficiency. All stationary phase presented few loss of the polymeric layer after the HPLC, indicating that this layer is well attached on the metalized support.

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.

Antimony is a common catalyst in the synthesis of polyethylene terephthalate used for food-grade bottles manufacturing. However, antimony residues in final products are transferred to juices, soft drinks or water. The literature reports mentions of toxicity associated to antimony. In this work, a green, fast and direct method to quantify antimony, sulfur, iron and copper, in PET bottles by X-ray fluorescence spectrometry is presented. 2.4 to 11 mg Sb kg-1 were found in 20 samples analyzed. The coupling of the multielemental technique to chemometric treatment provided also the possibility to classify PET samples between bottle-grade PET/recycled PET blends by Fe content.

This work proposes a simple, fast and inexpensive method to determine As in natural waters, using X-ray fluorescence. 50 µL of each sample containing 100 mg L-1 of yttrium as internal standard were deposited over a 2.5 µm thickness MylarTM film. The samples were dried at 50 °C for 2 h. X-ray spectra were obtained using an EDXRF apparatus. The accuracy was determined by analyte addition/recovery and by comparison with Hydride Generation Atomic Absorption Spectrometry (HG AAS). A recovery of about 100% was obtained and the results were in good agreement with HG AAS. The method showed a relative standard deviation of 6.8% and a detection limit of 10.5 µg L-1 of As.

Neste trabalho são relatados vários processos de oxidação para a degradação de acetonitrila. Foram investigadas alternativas como fotólise, degradação com peróxido de hidrogênio, processos Fenton e foto-Fenton. A fotólise, o processo mais simples e de menor custo dentre os avaliados, promoveu 100% de degradação de soluções aquosas de acetonitrila a 20%, após 30 horas de irradiação. Este método apresenta, portanto várias vantagens dentre as opções a serem usadas em processos de decomposição de resíduos tóxicos de acetonitrila, os quais tendem a se acumular em laboratórios que utilizam equipamentos de Cromatografia Líquida de Alta Eficiência com Fase Reversa.

Several oxidation processes were investigated to degrade residues of acetonitrile. Alternatives such as photolysis, degradation with hydrogen peroxide, Fenton and photo-Fenton processes were investigated. Among the options studied, photolysis proved to be the best choice. Photolysis promoted 100% degradation of 20% aqueous acetonitrile solutions in 30 hours. This method proved to be a cheap alternative to decompose toxic residues of acetonitrile, which tend to be accumulated in laboratories that use RP-HPLC equipments.

The objective of this work was to accomplish the simultaneous determination of some chemical elements by Energy Dispersive X-ray Fluorescence (EDXRF) Spectroscopy through multivariate calibration in several sample types. The multivariate calibration models were: Back Propagation neural network, Levemberg-Marquardt neural network and Radial Basis Function neural network, fuzzy modeling and Partial Least Squares Regression. The samples were soil standards, plant standards, and mixtures of lead and sulfur salts diluted in silica. The smallest Root Mean Square errors (RMS) were obtained with Back Propagation neural networks, which solved main EDXRF problems in a better way.

One of the main problems in quantitative analysis of complex samples by x-ray fluorescence is related to interelemental (or matrix) effects. These effects appear as a result of interactions among sample elements, affecting the x-ray emission intensity in a non-linear manner. Basically, two main effects occur; intensity absorption and enhancement. The combination of these effects can lead to serious problems. Many studies have been carried out proposing mathematical methods to correct for these effects. Basic concepts and the main correction methods are discussed here.