PRINCIPAL COMPONENT ANALYSIS (PCA) FOR CHEMICAL DATA EVALUATION AND HEAT MAPS PREPARATION: A TUTORIAL. This tutorial shows a step-by-step guide on handling big datasets using principal component analysis (PCA). A dataset of chemical elements’ concentration, emission spectrum, and energy-dispersive X-ray fluorescence (EDXRF) of e-waste were used as examples. Five routines were proposed to apply data processing and PCA calculation focusing data from laser-induced breakdown spectroscopy (LIBS), EDXRF, and heat maps preparation. These routines can be used in various softwares such as MatLab, Octave, R, and Python. PCA was applied in three examples; the first was for concentrations, and the other two were for spectra. An example of heat maps assembling a hyperspectral image of a printed circuit was also described. In addition, a playlist was created on YouTube using the available examples. Therefore, with this tutorial, it may be possible to learn how to deal with a large volume of data by applying PCA. The authors hope to contribute to those researching in the area.

MIXTURE DESIGN AND OPTIMUM REGION VISUALIZATION WITH SPREADSHEETS AT EXCEL: A TUTORIAL. This tutorial shows how to perform the data treatment for mixture design with two and multiple responses. Two data sets from the literature were used to exemplify the calculations. A template in Excel was proposed to prepare contour plot and response surface to visualize the optimum region of the mixture, which usually is made with commercial computational programs. The desirability function was used in example 2 (optimization of 5 responses simultaneously), and a code also available for download was proposed. Besides, 21 videos were prepared to show all the details for the readers and, it is available on YouTube. With this tutorial, it is possible to learn in a practical fashion how to handle the data from mixture design and, the authors hope to contribute with the researchers in this area.

This tutorial intends to show to the readers a step-by-step guide to perform a factorial design in their experiments. The examples used here cover most of doubts and questions related to teaching classes at graduation course. Free computational software was applied, as well as, codes were designed by the authors for the calculations. The complexity of each example is attached to the challenges and decisions that the experimentalist faces in its research. In addition, 24 videos were prepared to help the readers. The authors hope to foster the factorial design as an easy and helpful tool for chemists and general researchers in academia and industry.

Resumo Neste estudo, foi proposto um método para determinar a somatória das concentrações de inosina 5'-monofosfato (IMP) e guanosina 5'-monofosfato (GMP) em produtos finais e intermediários, através de uma combinação de espectroscopia UV e calibração multivariada. Na proposição do método, empregou-se Partial Least Squares (PLS), para a análise de dados, e os métodos propostos apresentaram erros em torno de 4 mg/L. Além disso, apresenta custo de análise 10 vezes menor quando comparado com o método cromatográfico de referência, sendo que a frequência analítica é de 20 amostras/hora.

Abstract This study proposed a method to determine the sum of the concentrations of inosine 5’-monophosphate (IMP) and guanosine 5’-monophosphate (GMP) in final and intermediate products through a combination of UV spectroscopy and multivariate calibration. Partial Least Squares regression (PLS regression) was used for the data analysis and the proposed methods presented errors of around 4 mg/L. In addition, the analysis cost is 10 times lower than the reference chromatographic method and the analytical frequency is 20 samples/hour.

Essential and toxic metals were determined in eighteen samples of medicinal herbs from Poland, Lithuania and Serbia by means of laser-induced breakdown spectroscopy (LIBS) and inductively coupled plasma optical emission spectrometry (ICP OES). Calcium, K and Mg concentrations were obtained in % (m/m) and other metals (Na, Co, Cu, Fe, Mn, Ni, Zn, Cd, Cr and Pb) in mg kg-1. The fact that the herb samples analyzed belonged to specific plant species and represented different morphological plant parts explained the characteristic distribution in two-dimensional scores plots obtained by principal component analysis (PCA). A strong correlation of LIBS results was achieved in comparison to those obtained by ICP OES for Ca, K and Mg. Differences in the types of infusions were observed, in that leaves are related to Zn and Ni concentrations, leaves and flowers to Co, Ca and Mn concentrations and flowers to K, Na, Mg and Fe content.

In order to evaluate the effects of environmental factors on the content of secondary metabolites, the chemical profiles of infusions from leaves of seven genotypes of Lippia gracilis Schauer, sourced from two locations (Sergipe and Bahia state) and collected during different seasons: summer (with and without irrigation) and winter, were determined by HPLC-DAD. The fingerprint chromatograms were analyzed by PCA to evaluate similarities and differences among the samples. Results revealed differences among genotypes collected and cultivated under the same conditions, suggesting that three genotypes have greater resistance to drought conditions.

A factorial design applied in a voltammetric stripping method for the measurement of Ag(I) in natural water is described. The procedure is based on the effective pre-concentration of silver ions on electrode surface. The calibration graph was linear in the silver concentration range from 7.92 x 10"7 to 1.07 x 10"5 mol L"1 with a detection limit of 3.81 x 10-7 mol L-1. The determination of Ag(I) in natural water samples was carried out satisfactory with the proposed electrode.

Alguns países, incluindo o Brasil (RDC 344, 2002), instituíram uma regulamentação indicando que farinhas de milho e trigo devem ser enriquecidas com ácido fólico e ferro. O principal objetivo deste trabalho foi a avaliação de algumas características de farinhas enriquecidas usando a Análise por Componentes Principais (PCA). Parâmetros como o teor de ácido fólico, ferro, proteína, lipídios, umidade, cinzas e carboidratos foram avaliados em 30 embalagens de farinhas adquiridas em comércio local. As farinhas de trigo e milho apresentaram, em média, composição centesimal aceitável de acordo com a Legislação Brasileira. Para as farinhas de trigo, a concentração de ácido fólico estava, em média, próxima ao esperado. As farinhas de milho continham quantidade superior da vitamina. Para os dois tipos de farinha, constatou-se teor de ferro acima do valor declarado no rótulo dos produtos. Uma matriz com 30 linhas (amostras) e 7 colunas (variáveis) foi organizada e os dados foram autoescalados. A primeira informação observada foi uma clara diferenciação entre os tipos de farinhas. As farinhas de trigo foram caracterizadas por maior quantidade de proteínas, umidade e cinzas. Por outro lado, as farinhas de milho apresentaram maior concentração de ferro, lipídios, carboidratos e ácido fólico. Foi possível notar também que farinhas acondicionadas em embalagens de plástico apresentaram menor quantidade de ácido fólico (152 µg.100 g-1, em média), quando comparadas às amostras armazenadas em embalagens de papel (259 µg.100 g-1, em média). Esse estudo pode fornecer ferramentas importantes para a avaliação dos programas de enriquecimento de alimentos com ácido fólico, principalmente, por apontar, preliminarmente, para a importância do tipo de embalagem para o acondicionamento das farinhas enriquecidas com a vitamina.

Some countries, including Brazil (resolution - RDC # 344, 2004), have issued a regulation stipulating that corn and wheat flours have to be fortified with folic acid and iron. The main objective of this work was to investigate some enriched flour characteristics using Principal Component Analysis (PCA). Wheat and corn flours presented, on average, acceptable centesimal composition according to the Brazilian Legislation. For the wheat flours investigated, the folic acid concentration was, on average, close to the expected value. Corn flours contained higher amount of vitamin. For both types of flour, the iron content exceeded the label claim of the products. Parameters, such as folic acid, iron, protein, lipids, moisture, ash, and carbohydrates content were present in 30 flour packages purchased from the local market. A matrix with 30 rows and 7 columns was organized and the data was autoscaled. The first information observed was an expected discrimination according to the type of flour. The wheat flours were characterized by high protein, moisture, and ash content. On the other hand, the corn flours had high iron, carbohydrates, lipids, and folic acid. Another important observation was related to the package type. It was noted that the flours packed in plastic bags had less folic acid (152 µg.100 g-1, on average) than those packed in paper (259 µg.100 g-1, on average) bags. This behavior is probably due to the light incidence during the storage period. This study can be useful to help the governmental authorities in the enriched food program evaluation. In this case, it will be possible to set suitable rules for appropriate food packaging.

Jundiaí river is the main stream in the Jundiaí Hydrographic Basin and its water is not considered safe for public supply. The water problem is getting worse with the development of the region. The Pirai stream, have been one of the last potable water resource. With the purpose of investigating the sediment quality, due to its influence on the water quality, bioavailable and total Cd and Pb were determined using TS-FF-AAS. Total Cd and Pb up to 2.47 and 24.7 µg g-1 were measured, respectively. The wastewater sludge showed concentrations of 4.01 and 171 µg g-1, for the same metals.

O ácido fólico tem sido identificado como uma das mais importantes vitaminas para a função normal do metabolismo humano. A deficiência de ferro é um sério problema de saúde que afeta uma grande proporção da população do mundo. No Brasil, foi publicada uma regulamentação indicando que farinhas de milho e trigo devem ser fortificadas com ácido fólico e ferro. O objetivo deste trabalho foi avaliar os níveis de ácido fólico e ferro em algumas farinhas enriquecidas. A quantificação de ambos nutrientes indicou que a concentração de ácido fólico variou entre 96 a 558 µg per 100 g (em milho) e 73 a 233 µg per 100g (em trigo) e de 3,8 a 8,7 mg per 100 g (em milho) e 4,6 a 7,4 mg per 100g (em trigo) para ferro. Portanto, a população brasileira parece estar exposta a concentrações inadequadas de ácido fólico e ferro quando farinhas de trigo e milho são consumidas.

Folic acid has been identified as one of the most important vitamins for normal human metabolic function. Iron deficiency is a serious health problem affecting a large proportion of the world population. In Brazil, an issue has been ruled requiring that corn and wheat flours must be fortified by the addition of folic acid and iron. The aim of this work was to evaluate the levels of folic acid and iron in some enriched flours. The successful quantification of both nutrients indicated that the levels of folic acid are in the range of 96 to 558 µg per 100g (in corn) and 73 to 233 µg per 100 g (in wheat) and from 3.8 to 8.7 mg per 100 g (in corn) and 4.6 to 7.4 mg per 100g (in wheat) for iron. Finally the Brazilian population seems to be exposed to inadequate concentrations of folic acid and iron when consuming enriched corn flours and some wheat flours.

O objetivo deste trabalho foi avaliar o teor de ferro e zinco e a composição centesimal de farinhas de trigo e milho enriquecidas. Para a avaliação das concentrações de ferro e zinco, aplicou-se a técnica de Espectrometria de Absorção Atômica com Chama. Foram utilizados os métodos oficiais de análise para a determinação de umidade, cinzas, proteínas, carboidratos e lipídeos. Os dados obtidos foram comparados aos valores declarados nos rótulos dos produtos e às especificações recomendadas pela Legislação Brasileira. A concentração de ferro estava acima do especificado para a maioria das amostras. O teor de zinco variou entre 0,6 e 1,5 mg/100 g. Constatou-se que todas as farinhas avaliadas apresentaram características físico-químicas compatíveis com a Legislação. Já em relação ao rótulo dos produtos, verificou-se haver variação entre os valores obtidos e aqueles apresentados na embalagem, para algumas amostras. Os resultados obtidos no trabalho são de grande importância para o alcance dos objetivos da obrigatoriedade do enriquecimento de farinhas.

The aim of this work was to evaluate iron and zinc content and centesimal composition of enriched wheat and corn flours. For iron and zinc evaluation the Flame Atomic Absorption Spectrometry was applied. Official methods of analysis were used for moisture, ash, proteins, carbohydrates and lipids. The obtained data were compared with values in the label of products and the specification recommended by Brazilian Legislation. Iron content was higher than those for most of samples. The amount of zinc varied between 0.6 e 1.5 mg/100 g. The evaluated flours presented physical-chemistry characteristics according to Legislation. However, about products label was the variation between obtained and presented in package values, for some samples, was confirmed. The obtained results are very important to achieve the objectives of the mandatory enrichment of flours.