Distin����o entre cacha��as destiladas em alambiques e em colunas usando quimiometria

One hundred fifteen cacha��a samples derived from distillation in copper stills (73) or in stainless steels (42) were analyzed for thirty five itens by chromatography and inductively coupled plasma optical emission spectrometry. The analytical data were treated through Factor Analysis (FA), Partial Least Square Discriminant Analysis (PLS-DA) and Quadratic Discriminant Analysis (QDA). The FA explained 66.0% of the database variance. PLS-DA showed that it is possible to distinguish between the two groups of cacha��as with 52.8% of the database variance. QDA was used to build up a classification model using acetaldehyde, ethyl carbamate, isobutyl alcohol, benzaldehyde, acetic acid and formaldehyde as chemical descriptors. The model presented 91.7% of accuracy on predicting the apparatus in which unknown samples were distilled.

Hidrocarbonetos polic��clicos arom��ticos (HPAS) em cacha��a, rum, u��sque e ��lcool combust��vel

The concentration of 15 polycyclic aromatic hydrocarbons (PAHs) in 57 samples of distillates (cacha��a, rum, whiskey, and alcohol fuel) has been determined by HPLC-Fluorescence detection. The quantitative analytical profile of PAHs treated by Partial Least Square - Discriminant Analysis (PLS-DA) provided a good classification of the studied spirits based on their PAHs content. Additionally, the classification of the sugar cane derivatives according to the harvest practice was obtained treating the analytical data by Linear Discriminant Analysis (LDA), using naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, benz[b]fluoranthene, and benz[g,h,i]perylene, as a chemical descriptors.

Quantitative structure-retention relationships analysis of retention index of essential oils

Genetic algorithm and multiple linear regression (GA-MLR), partial least square (GA-PLS), kernel PLS (GA-KPLS) and Levenberg-Marquardt artificial neural network (L-M ANN) techniques were used to investigate the correlation between retention index (RI) and descriptors for 116 diverse compounds in essential oils of six Stachys species. The correlation coefficient LGO-CV (Q��) between experimental and predicted RI for test set by GA-MLR, GA-PLS, GA-KPLS and L-M ANN was 0.886, 0.912, 0.937 and 0.964, respectively. This is the first research on the QSRR of the essential oil compounds against the RI using the GA-KPLS and L-M ANN.

Biodegrada����o de uma mistura de corantes t��xteis usando o fungo Ganoderma sp: um estudo cin��tico

The kinetics of biodegradation by the fungus Ganoderma sp of textile dyes Yellow, Blue and Red Procion were studied in effluents using UV-Vis spectroscopy, Partial Least Squares Regression (PLS) and univariate analysis. The kinetic of the reactions were founded intermediate between first and second orders and the rate constants were calculated. The biodegradation after 72 h at 28 ��C were 33.6, 43.5 and 57.7% for the dyes Yellow, Blue and Red Procion, respectively. The quantitative analysis of the effluent by HPLC method can not be used without previous separation.

Avalia����o da efici��ncia das t��cnicas ESI-MS e ATR/FTIR na determina����o de adultera����o de BX com querosene e ��leo residual

Direct infusion electrospray ionization mass spectrometry in the negative ion mode, ESI(-)-MS and Fourier transform infrared spectroscopy (FTIR) were used together with partial least squares (PLS) as a tool to determine B3 adulteration (B3 - mixture of 3% v/v of biodiesel in diesel) with kerosene and residual oil.

QSAR modeling: um novo pacote computacional open source para gerar e validar modelos QSAR

QSAR modeling is a novel computer program developed to generate and validate QSAR or QSPR (quantitative structure- activity or property relationships) models. With QSAR modeling, users can build partial least squares (PLS) regression models, perform variable selection with the ordered predictors selection (OPS) algorithm, and validate models by using y-randomization and leave-N-out cross validation. An additional new feature is outlier detection carried out by simultaneous comparison of sample leverage with the respective Studentized residuals. The program was developed using Java version 6, and runs on any operating system that supports Java Runtime Environment version 6. The use of the program is illustrated. This program is available for download at lqta.iqm.unicamp.br.

Experimento did��tico de quimiometria para calibra����o multivariada na determina����o de paracetamol em comprimidos comerciais utilizando espectroscopia no infravermelho pr��ximo: um tutorial, parte II

The aim of this manuscript was to show the basic concepts and practical application of Partial Least Squares (PLS) as a tutorial, using the Matlab computing environment for beginners, undergraduate and graduate students. As a practical example, the determination of the drug paracetamol in commercial tablets using Near-Infrared (NIR) spectroscopy and Partial Least Squares (PLS) regression was shown, an experiment that has been successfully carried out at the Chemical Institute of Campinas State University for chemistry undergraduate course students to introduce the basic concepts of multivariate calibration in a practical way.

Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy and chemometric techniques for the determination of adulteration in petrodiesel/biodiesel blends

We propose an analytical method based on fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy to detect the adulteration of petrodiesel and petrodiesel/palm biodiesel blends with African crude palm oil. The infrared spectral fingerprints from the sample analysis were used to perform principal components analysis (PCA) and to construct a prediction model using partial least squares (PLS) regression. The PCA results separated the samples into three groups, allowing identification of those subjected to adulteration with palm oil. The obtained model shows a good predictive capacity for determining the concentration of palm oil in petrodiesel/biodiesel blends. Advantages of the proposed method include cost-effectiveness and speed; it is also environmentally friendly.

UV determination of epinephrine, uric acid, and acetaminophen in pharmaceutical formulations and some human body fluids using multivariate calibration

In this work, a spectrophotometric methodology was applied in order to determine epinephrine (EP), uric acid (UA), and acetaminophen (AC) in pharmaceutical formulations and spiked human serum, plasma, and urine by using a multivariate approach. Multivariate calibration methods such as partial least squares (PLS) methods and its derivates were used to obtain a model for simultaneous determination of EP, UA and AC with good figures of merit and mixture design was in the range of 1.8 - 35.3, 1.7 - 16.8, and 1.5 - 12.1 ��g mL-1. The 2nd derivate PLS showed recoveries of 95.3 - 103.3, 93.3 - 104.0, and 94.0 - 105.5 ��g mL-1 for EP, UA, and AC, respectively.

Estudo do teste de Scott via t��cnicas espectrosc��picas: um m��todo alternativo para diferenciar cloridrato de coca��na e seus adulterantes

Cocaine is usually seized mixed with a wide variety of adulterants such as benzocaine, lidocaine, caffeine, and procaine. The forensic identification of cocaine in these street drug mixtures is normally performed using colorimetric testing kits, but these tests may suffer from interferences, producing false-positive results. Here, we describe the use of analytical techniques including attenuated total reflection Fourier transform infrared (ATR-FTIR) and ultraviolet-visible (UV-VIS) spectroscopies to distinguish between cocaine and other adulterants (lidocaine, promethazine, powdered milk and yeast) that yield positive results on the Scott test using the thiocyanate cobalt reagent. A further 13 substances were also analyzed using the Scott test.

DISCRIMINA����O DE MADEIRAS SIMILARES POR FLUORESC��NCIA MOLECULAR E M��NIMOS QUADRADOS PARCIAIS

Wood is an extremely complex biological material, which can show macroscopic similarities that make it difficult to discriminate between species. Discrimination between similar wood species can be achieved by either anatomic or instrumental methods, such as near infrared spectroscopy (NIR). Although different spectroscopy methods are currently available, few studies have applied them to discriminate between wood species. In this study, we applied a partial least squares-discriminant analysis (PLS-DA) model to evaluate the viability of using direct fluorescence measurements for discriminating between Eucalyptus grandis, Eucalyptus urograndis, and Cedrela odorata. The results show that molecular fluorescence is an efficient technique for discriminating between these visually similar wood species. With respect to calibration and the validation samples, we observed no misclassifications or outliers.

Determina����o simult��nea de NADH e ��cido asc��rbico usando voltametria de onda quadrada com eletrodo de carbono v��treo e calibra����o multivariada

O m��todo dos m��nimos quadrados parciais (PLS) foi aplicado aos dados obtidos por voltametria de onda quadrada para a determina����o simult��nea de ��cido asc��rbico (AA) e do co-fator b-nicotinamida adenina dinucleot��deo (NADH) em misturas sint��ticas. As curvas voltam��tricas foram obtidas em tamp��o fosfato 0,2 mol L-1 (pH 8,0). Foi poss��vel verificar que o m��todo PLS permite a determina����o destes compostos simultaneamente nas condi����es escolhidas. Os resultados mostraram um erro relativo m��ximo de 1,7% para o NADH e 2,1 % para o AA. A metodologia proposta �� simples e desenvolvimentos posteriores podem torn��-la ��til para an��lises in vivo.

Determination of sulfur in diesel using ATR/FTIR and multivariate calibration

The aim of this present work was to provide a more fast, simple and less expensive to analyze sulfur content in diesel samples than by the standard methods currently used. Thus, samples of diesel fuel with sulfur concentrations varying from 400 and 2500 mgkg-1 were analyzed by two methodologies: X-ray fluorescence, according to ASTM D4294 and by Fourier transform infrared spectrometry (FTIR). The spectral data obtained from FTIR were used to build multivariate calibration models by partial least squares (PLS). Four models were built in three different ways: 1) a model using the full spectra (665 to 4000 cm-1), 2) two models using some specific spectrum regions and 3) a model with variable selected by classic method of variable selection stepwise. The model obtained by variable selection stepwise and the model built with region spectra between 665 and 856 cm-1 and 1145 and 2717 cm-1 showed better results in the determination of sulfur content.

Influ��ncia da idade na gera����o de modelos de espectroscopia NIR, para predi����o de propriedades da madeira de Eucalyptus spp.

O objetivo deste trabalho foi o desenvolvimento de modelos NIRS para predizer as propriedades f��sicas e qu��micas de madeiras de Eucalyptus, com idades variando de 3 a 7 anos. Foram utilizadas 136 amostras e realizadas an��lises laboratoriais de densidade b��sica, teores de lignina e extrativos. Amostras de cavacos foram mo��das em moinho tipo ciclone, para coleta de espectros NIR. Os modelos foram desenvolvidos por regress��o de m��nimos quadrados parciais (PLS), sendo testadas transforma����es matem��ticas. Para valida����o dos modelos, foram utilizados grupos de amostras externas com diferentes idades, que n��o participaram no desenvolvimento do modelo. Os modelos desenvolvidos resultaram em consider��veis coeficientes de determina����o para densidade b��sica (R�� 0,84 a 0,89) e lignina (R�� 0,72 a 0,88), mas os melhores valores foram encontrados para o teor de extrativos (R�� 0,92 a 0,98). Pelos valores de rela����o de desempenho de desvio (RPD), verificou-se que amostras com idades diferentes das utilizadas no desenvolvimento dos modelos n��o apresentaram boas predi����es, exceto para densidade b��sica cujos modelos desenvolvidos especificamente para as idades de 3 e 7 anos, predisseram satisfatoriamente amostras com idades entre 4 e 6 anos.