The objective of this work was to develop a free access exploratory data analysis software application for academic use that is easy to install and can be handled without user-level programming due to extensive use of chemometrics and its association with applications that require purchased licenses or routines. The developed software, called Chemostat, employs Hierarchical Cluster Analysis (HCA), Principal Component Analysis (PCA), intervals Principal Component Analysis (iPCA), as well as correction methods, data transformation and outlier detection. The data can be imported from the clipboard, text files, ASCII or FT-IR Perkin-Elmer “.sp” files. It generates a variety of charts and tables that allow the analysis of results that can be exported in several formats. The main features of the software were tested using midinfrared and near-infrared spectra in vegetable oils and digital images obtained from different types of commercial diesel. In order to validate the software results, the same sets of data were analyzed using Matlab© and the results in both applications matched in various combinations. In addition to the desktop version, the reuse of algorithms allowed an online version to be provided that offers a unique experience on the web. Both applications are available in English.

Neste trabalho são apresentados modelos de regressão multivariada, empregando espectros por reflexão difusa no infravermelho com transformada de Fourier (DRIFTS), para análise quantitativa do sistema ternário formado pelos carbonatos de cálcio e magnésio e pelo óxido de magnésio. Através de um diagrama ternário, foram definidas as misturas para aquisição dos espectros por reflexão no infravermelho médio. Empregando-se a regressão por mínimos quadrados parciais (PLS), foram construídos modelos com os dados espectrais centrados na média e/ou escalados pela variância, utilizando o conjunto de espectros de calibração. Para selecionar os melhores modelos, foram comparados os valores de RMSEP (root mean square error of prediction). Os resultados comprovam que bons modelos de calibração multivariada para a determinação de carbonatos de cálcio e magnésio e de óxido de cálcio podem ser obtidos a partir dos espectros por reflexão no infravermelho. Estas determinações são particularmente úteis no estudo da decomposição térmica de rochas dolomíticas.

In the present work multivariate regression models were developed for the quantitative analysis of ternary systems using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) to determine the concentration in weight of calcium carbonate, magnesium carbonate and magnesium oxide. Nineteen spectra of standard samples previously defined in ternary diagram by mixture design were prepared and mid-infrared diffuse reflectance spectra were recorded. The partial least squares (PLS) regression method was applied to the model. The spectra set was preprocessed by either mean-centered and variance-scaled (model 2) or mean-centered only (model 1). The results based on the prediction performance of the external validation set expressed by RMSEP (root mean square error of prediction) demonstrated that it is possible to develop good models to simultaneously determine calcium carbonate, magnesium carbonate and magnesium oxide content in powdered samples that can be used in the study of the thermal decomposition of dolomite rocks.

A descarga de efluentes contendo metais pesados e cianeto pelas indústrias de galvanoplastia é uma das maiores fontes de poluição dos recursos hídricos. O emprego da técnica de eletrodiálise para o tratamento de um efluente sintético contendo aproximadamente 0,0089 mol L-1 de cádmio e 0,081 mol L-1 de cianeto foi estudado utilizando uma célula de eletrodiálise de cinco compartimentos. Os resultados demonstram que a remoção de cádmio e cianeto depende da densidade de corrente aplicada e é limitada pela precipitação de cádmio sobre a membrana catiônica.

The discharge of galvanic industry wastewaters containing heavy metals and cyanide is one of the largest sources of water pollution. The use of the electrodialysis technique for the treatment of a synthetic wastewater containing approximately 0.0089 mol L-1 cadmium and 0.081 mol L-1 cyanide was studied using a five-compartment electrodialysis cell. The results demonstrate that the removal of cadmium and cyanide depends on the applied current density and it is limited by the precipitation of cadmium on the cation-exchange membrane in the diluate central cell compartment.