Paula Fernandes de Aguiar

Metodologia analítica para quantificar o teor de biodiesel na mistura biodiesel:diesel utilizando espectroscopia na região do infravermelho

Considered the best substitute for diesel, biodiesel can be blended with diesel in any ratio, bringing lots of environmental, economic and social advantages. Brazilian law No 11097/2005, proposes the introduction of biodiesel in to the Brazilian energy matrix, mixed with diesel at a minimum percentage of 2%. For consumers and sellers to be sure that the commercialized mixture of biodiesel:diesel contains the correct percentage, it is necessary to develop analytical methodologies to quantify the amount of biodiesel added. This work presents a fast, low-cost and simple methodology to determine the biodiesel proportion in mixtures of biodiesel:diesel, based on infrared spectroscopy.

Validation of impregnation process for homeopathic globules by spectrophotometric-UV method

We compared the impregnation techniques for globules according to the Manual of Technical Norms for Homeopathic Pharmacies (MNTFH) of the Association of Homeopathic Pharmacists (ABFH), Brazilian Homeopathic Pharmacopoeia (FHB) and variations of these techniques. The variables were evaluated in this procedure, three different sizes of globules (N o . 3, 5 and 7), the hydroalcoholic solution of 70% (v/v) Minoxidil 2% (w/v) was used to impregnate the globules in concentrations of 2, 3, 4, 5% (v/w) and the impregnation at 10 %(v/w) was used hydroalcoholic solutions at 70, 80 and 90% (v/v), and four impregnation techniques various ( A -glass, B -paper, C -cup and D -FHB). As the results of content uniformity did not demonstrate a normal distribution, the one way ANOVA and a nonparametric statistical model were used for evaluation. Considering the average, the standard deviation (SD), the individual variance of each group and the principal components analysis graphs (PCA), it was observed that the “A” impregnation of globules technique, with 5% (v/w) of the impregnation concentrations and the No.5 globule presented the best uniformity of dose. As to the drying, there was a need to use a heat source.

Influence of processing parameters on structural characteristics of porous calcium phosphate samples: a study using an experimental design method

Synthetic porous ceramics can be used as three-dimensional scaffolds for bone repair. The aim of this work is to correlate process parameters with scaffolds structural characteristics. The factorial 2 level experimental design was chosen to study the effect of the Ca/P ratio (1.58 or 1.67), calcination temperature (1000 or 1150 °C) and porogen content (20 or 40%) on the calcium phosphate samples characteristics. The influence of such parameters was determined by X-ray diffraction, infrared spectroscopy and image analysis. It was observed that phase composition was basically a function of the Ca/P ratio of the raw material. The use of the porogen did not alter the hydroxyapatite (HA)/tricalcium phosphate (TCP) content, but induced changes in the relative content of TCP phase (a or b). It is possible to design a porous sample with defined characteristics, and the model herein used can be considered as having a good predictive power.

Phenolic compounds of Brazilian beers from different types and styles and application of chemometrics for modeling antioxidant capacity.

In the present study we aimed at investigating, for the first time, phenolic compounds in Brazilian beers of different types and styles. We also aimed at applying chemometrics for modeling beers antioxidant capacity as a function of their physicochemical attributes (density, refractive index, bitterness and ethanol content). Samples (n=29) were analyzed by PCA originating five groups, especially according to ethanol contents and bitterness. In general, Group V (alcoholic beers with very high bitterness) presented higher refractive index, bitterness, ethanol and phenolics contents than Groups I (non-alcoholic beers) and II (alcoholic beers with low bitterness). Brazilian beers phenolics profile was distinct from that of European beers, with high contents of gallic acid (0.5-14.7 mg/L) and low contents of ferulic acid (0.2-1.8 mg/L). Using PLS, beers antioxidant capacity measured by FRAP assay could be predicted with acceptable precision by data of ethanol content and density, bitterness and refractive index values.

VALIDAÇÃO DA METODOLOGIA DA AVALIAÇÃO DE INCERTEZA EM CURVAS DE CALIBRAÇÃO MELHOR AJUSTADAS POR POLINÔMIOS DE SEGUNDO GRAU

The most widespread literature for the evaluation of uncertainty - GUM and Eurachem - does not describe explicitly how to deal with uncertainty of the concentration coming from non-linear calibration curves. This work had the objective of describing and validating a methodology, as recommended by the recent GUM Supplement approach, to evaluate the uncertainty through polynomial models of the second order. In the uncertainty determination of the concentration of benzatone (C) by chromatography, it is observed that the uncertainty of measurement between the methodology proposed and Monte Carlo Simulation, does not diverge by more than 0.0005 unit, thus validating the model proposed for one significant digit.

Comparação de diferentes abordagens para avaliação da incerteza na cromatografia gasosa do gás natural

The evaluation of uncertainty associated with an analytic result is an essential part of the measurement process. Recently, several approaches to evaluate the uncertainty in measurement have been developed. Here, the gas chromatography assay uncertainty for natural gas is compared by some of these approaches: the guide to the expression of uncertainty in measurement (GUM) approach, top-down approach (reproducibility estimate from an inter-laboratory study), Barwick & Ellison (data from validation), study of variability and fuzzy approach. The comparison shows that GUM, Barwick & Ellison and fuzzy approaches lead to comparable uncertainty evaluations, which does not happen with the top-down approach and study of variability by the absence of data normality.

Production of Bacillus sphaericus Entomopathogenic Biomass Using Brewery Residues

The use of brewery residues—yeast and trub—has been evaluated aiming to minimize the costs of the industrial production of Bacillus sphaericus-based bioinsecticide. Both brewery residues promoted growth and sporulation of the three B. sphaericus strains that were isolated from Brazilian soils (S1, S2, and S20). However, distinct growth and sporulation behaviors were observed in relation to the different nutritional conditions and strain used. The maximum sporulation percentage was obtained through the cultivation of S20 strain in brewery residual yeast. In general, the entomopathogenic biomasses produced showed good results for toxicity to Culex larvae. The minimum values of larvae population (LC50) were observed for the S20 strain grown on yeast brewery residue-containing media. After fermentation, a considerable decrease in the organic material of alternative media was verified, although the residual values were still higher than that considered appropriate for effluent discharge.

Least squares regression with errors in both variables: case studies

Analytical curves are normally obtained from discrete data by least squares regression. The least squares regression of data involving significant error in both x and y values should not be implemented by ordinary least squares (OLS). In this work, the use of orthogonal distance regression (ODR) is discussed as an alternative approach in order to take into account the error in the x variable. Four examples are presented to illustrate deviation between the results from both regression methods. The examples studied show that, in some situations, ODR coefficients must substitute for those of OLS, and, in other situations, the difference is not significant.

Brewery Wastes Reuse for Protease Production by Lactic Acid Bacteria Fermentation

This study evaluated the use of three solid brewery wastes: brewers spent grain, hot trub and residual brewers yeast, as alternative media for the cultivation of lactic acid bacteria to evaluate their potential for proteolytic enzyme production. Initially, a mixture experimental design was used to evaluate the effect of each residue, as well as different mixtures (with the protein content set at 4%) in the enzyme production. At predetermined intervals, the solid and liquid fractions were separated and the extracellular proteolytic activity was determined. After selecting the best experimental conditions, a second experiment, factorial experimental design, was developed in order to evaluate the protein content in the media (1 to 7%) and the addition of fermentable sugar (glucose, 1 to 7%). Among the wastes, residual yeast showed the highest potential for the production of extracellular enzymes, generating a proteolytic extract with 2.6 U/mL in 3 h. However, due to the low content of the fermentable sugars in the medium, the addition of glucose also had a positive effect, increasing the proteolytic activity to 4.9 U/mL. The best experimental conditions of each experimental design were reproduced for comparison, and the enzyme content was separated by ethanol precipitation. The best medium produced a precipitated protein with proteolytic activity of 145.5 U/g.

Evaluation of the chemical composition of the essential oil from a Brazilian Poejo, Hesperozygis myrtoides (St. Hill ex Benth.) Epling at different collection periods and sites

Abstract Hesperozygis myrtoides is a native species from Cerrado and Atlantic Forest of Brazil. The essential oil from aerial parts of this plant, collected at different periods of the year, was obtained by hydrodistillation and analyzed by GC and CG-MS. The most abundant compounds were limonene (2.1–22.7%), isomenthone (14.3–47.7%), neo-isomenthol (1.8–4.4%), pulegone (19.8–57.3%) and isomenthyl acetate (0.3–14.3%). The chromatographic data were processed using hierarchical cluster analysis (HCA) and principal component analysis (PCA) based on the major compounds. The multivariate analyses (MVA) indicated that the variation of chemical composition of principal substances of H. myrtoides essential oil depends on the altitude. The enantiomeric distribution of (R)-(+)-pulegone and (+)-isomenthone were established for the first time for this essential oil by bidimensional GC-chiral analysis.