Adilson Ben da Costa

Fourier Transform Infrared Spectroscopy (FTIR) and Multivariate Analysis for Identification of Different Vegetable Oils Used in Biodiesel Production

The main objective of this study was to use infrared spectroscopy to identify vegetable oils used as raw material for biodiesel production and apply multivariate analysis to the data. Six different vegetable oil sources—canola, cotton, corn, palm, sunflower and soybeans—were used to produce biodiesel batches. The spectra were acquired by Fourier transform infrared spectroscopy using a universal attenuated total reflectance sensor (FTIR-UATR). For the multivariate analysis principal component analysis (PCA), hierarchical cluster analysis (HCA), interval principal component analysis (iPCA) and soft independent modeling of class analogy (SIMCA) were used. The results indicate that is possible to develop a methodology to identify vegetable oils used as raw material in the production of biodiesel by FTIR-UATR applying multivariate analysis. It was also observed that the iPCA found the best spectral range for separation of biodiesel batches using FTIR-UATR data, and with this result, the SIMCA method classified 100% of the soybean biodiesel samples.

Cadmium determination in biological samples by direct solid sampling flame atomic absorption spectrometry

Abstract A direct solid sampling flame atomic absorption spectrometric procedure for trace determination of cadmium in biological samples has been developed. Test samples (0.05–2.00 mg) were ground and weighed into small polyethylene vials, which were connected to the device for solid sample introduction into a conventional air/acetylene flame. Test samples were carried as a dry aerosol to a quartz cell, placed between the burner and the optical path, which had a perpendicular entrance and a slit in the upper part. The atomic vapor generated in the flame produced a transient signal that was totally integrated within 1 s. The effect of operating conditions and the extent of grinding on the analytical signal were evaluated. Background signals were always low and a characteristic mass of 0.29 ng Cd was obtained. Calibration was performed using different masses of solid certified reference materials. Results obtained for certified and in-house reference materials were typically within the 95% confidence interval of the certified and/or reference value, and the precision, expressed as relative standard deviation, was between 3.8 and 6.7%. The proposed system is simple and it might be adapted to conventional atomic absorption spectrometers allowing the determination of Cd in more than 80 test samples per hour, excluding weighing.

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.

Direct cadmium determination in sediment samples by flame atomic absorption spectrometry using multivariate calibration procedures

A direct solid sampling procedure by flame atomic absorption spectrometry (DSA-FAAS) has been developed for the determination of cadmium in marine and river sediment samples. Multivariate calibration using the partial least squares (PLS) regression procedure was applied to calibration using dry sediment reference samples. Test-samples were introduced into the flame as a dry aerosol using a T-quartz cell set between the burner and the optical path. Background signals were always low and a characteristic mass of 0.21 ng Cd was found and an absolute limit of detection of 0.25 ng (3s), or 0.25 µg g−1 if a sample mass of 1 mg was used. Using the proposed multivariate calibration procedure the results were considered satisfactory regarding both agreement with the results from reference samples (from 96.8 to 101.7%) and precision (relative standard deviation from 5.5 to 7.0%). With this procedure errors occurring when conventional univariate calibration was used (up to 64%) were reduced to less than 4%.

CHEMOSTAT, UM SOFTWARE GRATUITO PARA ANÁLISE EXPLORATÓRIA DE DADOS MULTIVARIADOS

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.

Element Determination in Pharmaceuticals Using Direct Solid Analysis- Electrothermal Vaporization Inductively Coupled Plasma Optical Emission Spectrometry

A solid sampling electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP OES) method for determination of As, Cd, Cr, Cu, Mn, Mo, Ni, Pb, Pd, Pt, Rh, Ru and V in pharmaceuticals is proposed. Tricyclic pharmaceuticals were directly analyzed due to their difficult decomposition with acids. Pyrolysis and vaporization temperature, sample mass, and reaction gas (Freon) flow rate were evaluated. The effect of organic and inorganic compounds was evaluated for matrix matching. The limits of detection ranged from 0.04 µg g−1 (Cu) to 107 µg g−1 (As) and the relative standard deviation was lower than 10%. The investigated elements were not detected in the analyzed samples with the exception of Cr in cyclobenzaprine hydrochloride. Since there was no certified reference materials available for metals and metalloids in pharmaceuticals, the accuracy of the method was evaluated by an independent technique and by analyte recovery. Inductively coupled plasma mass spectrometry was employed for analyte determination after sample decomposition by microwave induced combustion. The agreement of the results found by both techniques was better than 87% and analyte recoveries ranged from 91 to 103%.

PhotoMetrix: An Application for Univariate Calibration and Principal Components Analysis Using Colorimetry on Mobile Devices

This article describes the development of a mobile colorimetric analysis tool. The application, called PhotoMetrix, employs the techniques of simple linear correlation for univariate analysis and principal components analysis (PCA) for multivariate exploratory analysis. The image data are captured by the main camera of the device and converted into red, green and blue (RGB) histograms. As regards the application, the iron determinations were performed in vitamin supplements (univariate module) and differentiation of banknotes was performed by PCA (multivariate module). For the iron determinations, three samples of vitamins at concentrations of 14, 40 and 50 mg of iron per tablet were tested and the results were not statistically significant (p > 0.05) compared to the reference method. The differentiation of banknotes was performed on Brazilian and Argentinean banknotes. The results showed clustering of the same types of banknotes, and through the loadings graph it was possible to observe the variables through the formation of clusters.

Direct solid sampling by flame atomic absorption spectrometry: determination of manganese in coal samples

A new device for the direct solid analysis by flame atomic absorption spectrometry was investigated as an alternative technique for the determination of trace elements in coal. The potential application of the proposed procedure for the determination of manganese was investigated. Ground coal test samples were weighed directly into polyethylene vials and carried as a dry aerosol to a slotted quartz vaporization cell placed between the flame burner and optical path. The transient signals obtained were totally integrated in 1 second. The effect of operating conditions on the analytical signal was investigated. Background signals were always low and a Mn characteristic mass of 1.9 ng was found. Results were considered satisfactory regarding to both accuracy (between 97.5 and 103.2%) and precision (RSD better than 6%). The proposed system is simple and can be easily adapted to any conventional atomic absorption spectrometers allowing the analysis of more than 80 test samples in an hour.

Determination of Propranolol Hydrochloride in Pharmaceutical Preparations Using Near Infrared Spectrometry with Fiber Optic Probe and Multivariate Calibration Methods

A method for determination of propranolol hydrochloride in pharmaceutical preparation using near infrared spectrometry with fiber optic probe (FTNIR/PROBE) and combined with chemometric methods was developed. Calibration models were developed using two variable selection models: interval partial least squares (iPLS) and synergy interval partial least squares (siPLS). The treatments based on the mean centered data and multiplicative scatter correction (MSC) were selected for models construction. A root mean square error of prediction (RMSEP) of 8.2 mg g−1 was achieved using siPLS (s2i20PLS) algorithm with spectra divided into 20 intervals and combination of 2 intervals (8501 to 8801 and 5201 to 5501 cm−1). Results obtained by the proposed method were compared with those using the pharmacopoeia reference method and significant difference was not observed. Therefore, proposed method allowed a fast, precise, and accurate determination of propranolol hydrochloride in pharmaceutical preparations. Furthermore, it is possible to carry out on-line analysis of this active principle in pharmaceutical formulations with use of fiber optic probe.

Environmental pathways and human exposure to manganese in southern Brazil

The study of environmental pathways and human exposure to Manganese (Mn) in Southern Brazil was performed using two steps. The first step consisted of taking water samples from the surface of the Pardinho River. The average results from this technique showed a significant increase of pollutants, including increased levels of Mn, above the environmentally acceptable standard recommended by the Brazilian National Environment Council. Additionally, 64 soil samples were taken from areas with and without agricultural activity. Many results were above the mean crust and did not indicate significant differences of Mn levels between the sampled areas. For the second step, 12 families were selected and assessed for exposure to Mn in a region with high levels of Mn in the soil. Most of the analyzed foods contained amounts of Mn above the reference values, indicating that food can be an important source of exposure. The Mn content from the hair of most subjects studied was also high compared to reference values from non-exposed populations. Although the contamination appeared to come from a natural origin, the results found in the present study showed that the Mn levels present in the Pardinho River Basin are a relevant public health issue.