Marco Flôres Ferrão

Total sulfur determination in residues of crude oil distillation using FT-IR/ATR and variable selection methods.

Total sulfur concentration was determined in atmospheric residue (AR) and vacuum residue (VR) samples obtained from petroleum distillation process by Fourier transform infrared spectroscopy with attenuated total reflectance (FT-IR/ATR) in association with chemometric methods. Calibration and prediction set consisted of 40 and 20 samples, respectively. Calibration models were developed using two variable selection models: interval partial least squares (iPLS) and synergy interval partial least squares (siPLS). Different treatments and pre-processing steps were also evaluated for the development of models. The pre-treatment based on multiplicative scatter correction (MSC) and the mean centered data were selected for models construction. The use of siPLS as variable selection method provided a model with root mean square error of prediction (RMSEP) values significantly better than those obtained by PLS model using all variables. The best model was obtained using siPLS algorithm with spectra divided in 20 intervals and combinations of 3 intervals (911-824, 823-736 and 737-650 cm(-1)). This model produced a RMSECV of 400 mg kg(-1) S and RMSEP of 420 mg kg(-1) S, showing a correlation coefficient of 0.990.

Development of methodology for identification the nature of the polyphenolic extracts by FTIR associated with multivariate analysis

Tannins are polyphenolic compounds of complex structures formed by secondary metabolism in several plants. These polyphenolic compounds have different applications, such as drugs, anti-corrosion agents, flocculants, and tanning agents. This study analyses six different type of polyphenolic extracts by Fourier transform infrared spectroscopy (FTIR) combined with multivariate analysis. Through both principal component analysis (PCA) and hierarchical cluster analysis (HCA), we observed well-defined separation between condensed (quebracho and black wattle) and hydrolysable (valonea, chestnut, myrobalan, and tara) tannins. For hydrolysable tannins, it was also possible to observe the formation of two different subgroups between samples of chestnut and valonea and between samples of tara and myrobalan. Among all samples analysed, the chestnut and valonea showed the greatest similarity, indicating that these extracts contain equivalent chemical compositions and structure and, therefore, similar properties.

Profiling cocaine by ATR–FTIR

In this article, five hundred and thirteen cocaine seizures of the State of Rio Grande do Sul (Brazil) were analyzed by Fourier transform infrared spectroscopy (FT-IR) in the fingerprint region (1800-650 cm(-1)) to profiling and evaluate the pharmaceutical products used as adulterants. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) were used to identify patterns among the samples whereas partial least square discriminant analysis (PLS-DA) and support vector machines discriminant analysis (SVM-DA) were used to classification the cocaine between base and salt. Spectra of standard solid mixtures of cocaine (salt and base), phenacetin, lidocaine and caffeine were used associated with PCA to predict qualitatively the profile of cocaine seizure. In HCA and PCA, salt and base group were formed correctly. Accordingly with predicted profile of the salt samples, they were majority adulterated with caffeine and lidocaine whereas base cocaine was adulterated only with phenacetin. In the discrimant analysis, all methods have classified the cocaine samples correctly with sensitivity and specificity equal to one between salt and base.

Attenuated total reflectance with Fourier transform infrared spectroscopy (ATR/FTIR) and different PLS Algorithms for simultaneous determination of clavulanic acid and amoxicillin in powder pharmaceutical formulation

A method for simultaneous determination of clavulanic acid (CA) and amoxicillin (AMO) was developed using Fourier transform mid infrared technique coupled with attenuated total reflectance (ATR/FTIR) accessory. 27 samples were used as calibration set and 8 samples were used for prediction set. Calibration models were developed using partial least squares (PLS), interval PLS (iPLS), synergy PLS (siPLS) and backward PLS (biPLS). Multiplicative scatter correction and the mean centering were used and produced the best models. Relative standard error of prediction (RSEP) of 3.8% for CA and 5.1% for AMO were obtained using biPLS algorithm for ATR/FTIR data. Results obtained by the proposed methodology were compared with those using high performance liquid chromatography (HPLC) and no significant differences were obtained. The proposed method using ATR/FTIR combined to multivariate analysis methods was suitable for the simultaneous determination of CA and AMO in commercial pharmaceutical products.

Detection of the origin of Brazilian wines based on the determination of only four elements using high-resolution continuum source flame AAS.

A method has been developed to determine 10 elements in Brazilian red wines using high-resolution continuum source flame atomic absorption spectrometry, a technique that allows the fast sequential determination of an essentially unlimited number of elements per sample, each one under previously optimized conditions. All measurements were made without sample preparation, using aqueous standard solutions for calibration. The results were in agreement within 99% of confidence (t-test) with those obtained by inductively coupled plasma optical emission spectrometry. The same grape, Cabernet sauvignon, was used in all experiments, and the wines from each region were prepared especially for this investigation in order to avoid any confusion due to grapes from other regions, which are often used in commercial wines. The elements K, Mn, Rb and Sr were found to be the best indicators for the origin of the wines, based on a Principal Component Analysis.

Methods of multivariate analysis of NIR reflectance spectra for classification of yerba mate

The present article is about a method of classification for yerba mate (Ilex paraguariensis), native to South America. Yerba mate samples were ground in a cryogenic mill and the near-infrared (NIR) reflectance of milled samples was directly measured. Hierarchical cluster analysis (HCA), principal components analysis (PCA), k-nearest neighbour (kNN), soft independent modelling class analogy (SIMCA), partial least square discriminant analysis (PLS-DA), and support vector machine discriminant analysis (SVM-DA) were used for multivariate analysis of the NIR reflectance spectra. Fifty-four brands of yerba mate from Argentina, Brazil, Paraguay and Uruguay were analyzed to classify the commercialized product by country of origin. For all intervals of the NIR reflectance spectrum evaluated (4435–4318 cm−1, 4358–4200 cm−1, 4436–4200 cm−1, and 4673–4200 cm−1), the SVM-DA classification of all brands was 100% correct. The kNN classification was not 100% correct in any interval. Classification via PCA, HCA and SIMCA was 100% correct for the 4435–4318 cm−1 interval. PLS-DA classification was 100% correct for the 4358–4200 cm−1 and 4435–4318 cm−1 intervals.

Direct determination of tannins in Acacia mearnsii bark using near-infrared spectroscopy

This study investigated the application of near-infrared spectroscopy (NIRS) and multivariate calibration methods to the direct determination of the tannin content in Acacia mearnsii bark to improve control during the tannin extraction process. Eighty-nine bark samples were collected from the industrial plant of an extractive tannin industry. The NIR spectra were acquired using an FT-NIR spectrometer with an integrating sphere, an indium–gallium–arsenic detector in the range 7500–4000 cm−1, a resolution of 16 cm−1 and 32 scans divided in two different ways: (a) in natura samples (no sample processing); and (b) dried and milled samples. Partial least-squares models were developed and different strategies were investigated during pre-processing of the IR spectra. The results of the prediction were compared with those obtained using the reference methodology (NBR 11131) and gave values for the root mean square error of prediction between 2.11 and 2.42% for the dried and milled bark samples and between 2.31 and 2.54% for the in natura samples. These results show that NIRS combined with multivariate calibration methods may be used for the direct determination of the tannin content in Acacia mearnsii bark. The requirement for little sample preparation, a short analysis time, no reagent consumption and, consequently, no waste generation are the main positive characteristics of the proposed method.

Films based on neutralized chitosan citrate as innovative composition for cosmetic application

In this work, citrate and acetate buffers, were investigated as neutralizers to chitosan salts in order to provide biocompatible and stable films. To choose the appropriate film composition for this study, neutralized chitosan citrate and acetate films, with and without the plasticizer glycerol, were prepared and characterized by thickness, moisture content, degree of swelling, total soluble matter in acid medium, simultaneous thermal analysis and differential scanning calorimetry. Chitosan films neutralized in citrate buffer showed greater physical integrity resulted from greater thicknesses, lower moisture absorbance, lower tendency to solubility in the acid medium, and better swelling capacities. According to thermal analyses, these films had higher interaction with water which is considered an important feature for cosmetic application. Since the composition prepared in citrate buffer without glycerol was considered to present better physical integrity, it was applied to investigate hyaluronic acid release in a skin model. Skins treated with those films, with or without hyaluronic acid, show stratum corneum desquamation and hydration within 10min. The results suggest that the neutralized chitosan citrate film prepared without glycerol promotes a cosmetic effect for skin exfoliation in the presence or absence of hyaluronic acid.

A rapid and non-invasive method for the classification of natural tannin extracts by near-infrared spectroscopy and PLS-DA

Vegetable tannins are plant extracts that have traditionally been used to tan leather. These extracts are polyphenolic compounds that are widely distributed in plants and have the ability to precipitate proteins since their structures are rich in hydroxyls. Tannins can be classified into two groups: the hydrolyzable tannins and the proanthocyanidins, also called condensed tannins. In this study, 49 samples of vegetable tannin extracts, representing six commercially available types, were analyzed by near infrared and multivariate analyses (HCA and PLS-DA). The first derivative of the NIR spectra proved useful in the differentiation of the extracts, as it provided information on the main absorption bands, which are related to the chemical composition and structure. A well-defined separation between condensed (quebracho and mimosa) and hydrolyzable tannins (tara, myrobalan, chestnut and valonea) was observed by HCA (unsupervised method). The PLS-DA supervised method showed excellent results regarding classification, with a sensitivity and specificity of 100%. From the results, we concluded that this method may be useful for the quality control of commercial tannins and correct identification, as well as in mitigating fraud since other extracts and products can also be detected.

Seized cannabis seeds cultivated in greenhouse: A chemical study by gas chromatography-mass spectrometry and chemometric analysis.

Cannabis sativa L. is cultivated in most regions of the world. In 2013, the Brazilian Federal Police (BFP) reported 220 tons of marijuana seized and about 800,000 cannabis plants eradicated. Efforts to eradicate cannabis production may have contributed to the development of a new form of international drug trafficking in Brazil: the sending of cannabis seeds in small amounts to urban centers by logistics postal. This new and increasing panorama of cannabis trafficking in Brazil, encouraged the chemical study of cannabis seeds cultivated in greenhouses by gas-chromatography coupled with mass spectrometry (GC-MS) associated with exploratory and discriminant analysis. Fifty cannabis seeds of different varieties and brands, seized by the BFP were cultivated under predefined conditions for a period of 4.5 weeks, 5.5 weeks, 7.5 weeks, 10 weeks and 12 weeks. Aerial parts were analyzed and cannabigerol, cannabinol, cannabidiol, cannabichromene Δ9-tetrahydrocannabinol (THC) and other terpenoids were detected. The chromatographic chemical profiles of the samples were significantly different, probably due to different variety, light exposition and age. THC content increased with the age of the plant, however, for other cannabinoids, this correlation was not observed. The chromatograms were plotted in a matrix with 50 rows (samples) and 3886 columns (abundance in a retention time) and submitted to PCA, HCA and PLS-DA after pretreatment (normalization, first derivative and autoscale). The PCA and HCA showed age separation between samples however it was not possible to verify the separation by varieties and brands. The PLS-DA classification provides a satisfactory prediction of plant age.