In this paper, a fast, simple and new alternative method for determination of water content (moisture) in biodiesel using electrochemical impedance spectroscopy (EIS) is developed. The method is based on the sensitive variation of the charge transfer resistance (R) of the biodiesel medium in the presence of different quantities of water. To obtain an accurate analytical measurement, a pre-treatment based on a simple dilution by acetonitrile is employed. The two identical Pt electrodes are used in the measurement cell filled with sample solution. The experiment conditions are also optimized for the measurements. The obtained analytical linear curve between the water content and EIS impedance is the basis for the water content analysis in biodesiel fuel. The EIS method is then successfully applied to both real and certified samples, and the results confirm that the method is reliable with high sensitivity, precision and accuracy. The comparison of EIS method with the official standard method is also made through the Student test t, demonstrating that both methods are statistically consistent and similars. The validation of such an EIS method confirms that the method presented for the fist time in this paper can be succesessfully applied to determining the water content of biodiesel fuel.
A sensor based in a graphite–polyurethane composite electrode modified with the mesoporous nanostructured silica with hexagonal array of pores called Santa Barbara Amorphous type material (SBA‐15) containing nickel was built. The presence of Ni, incorporated during the synthesis of SBA‐15, resulted in an increase in sensitivity when compared to the other electrodes based on the unmodified SBA‐15. A procedure was proposed for the determination of Cu2+ in ethanol biofuel by square wave stripping voltammetry with linear response in concentration levels of 1.0×10−8 and 1.0×10−7 mol L−1, resulting in a limit of detection of 1.83×10−10 mol L−1 and precision (RSD) of 2.09 %.
Biodiesel can be altered when exposed to air, light,
temperature,
and humidity. Other factors, such as microbial or inorganic agents,
also interfere with the quality of the product. In the present work,
the Rancimat method and mid-infrared spectroscopy associated with
chemometry, were used to identify the oxidation process of biodiesel
from different feedstocks and to evaluate the antioxidant activity
of butylated hydroxytoluene. The study was carried out in four steps:
preparation of biodiesel samples with and without the antioxidant
agent, degradation of the samples under the effect of light and heating
at 70 °C, measurements of the induction period, obtention of
infrared spectra, and multivariate analysis. The Fourier transform
mid-infrared spectroscopy was used in combination with multivariate
analysis, using techniques such as principal component analysis (PCA)
and hierarchical clustering analysis (HCA). The Rancimat results showed
that babassu biodiesel has a higher resistance to oxidative degradation,
while chicken biodiesel is the most susceptible to degradation; on
the other hand, the antioxidant activity was more effective with chicken
biodiesel, demonstrating that the antioxidant effect depends on the
feedstock used in the production of biodiesel. The oxidative stability
of babassu oil-, corn oil-, and chicken fat-based biodiesels decreased
during storage both in the presence of light and at high temperature.
Prior to PCA, all spectra were pre-processed with a combination of
Savitzky–Golay smoothing filter with a 7-point window, baseline
correction, and mean-centered data. The use of mid-infrared spectroscopy
associated with PCA revealed the first two components to explain the
greater variability of data, representing over 75% of total variation
for all analyzed systems. In addition, it was able to separate the
biodiesel samples according to the fatty acid profile of its feedstock,
as well as the type of degradation to which it was subjected, the
same being confirmed by HCA.
The contamination of water and soil by petroleum hydrocarbons is reported quite frequently, mainly due to accidents involving transport and storage of fuels. Among the most toxic compounds the most volatile benzene, toluene, ethylbenzene and xylene (BTEX). Residues of these compounds can cause serious environmental and public health troubles. Thus, more sensitive, selective and low-cost techniques, focused on the analysis and monitoring of these contaminants are being developed in order to establish operational control and to comply with local laws, but the intellectual property of such technologies is still unknown. The present study shows the panorama about patents, thesis and dissertations which have been already published on this theme. Together, the United States and China hold the largest number of patents, and most of thesis/dissertations describe methodologies for BTEX detection in water, although numerous environmental problems caused by oils in the soil had been reported. Also, the methods based on chromatographic techniques stand out in relation to the other techniques. It was possible to verify important advances in the field of sensors, especially the electrochemical ones, in order to solve the analytical gaps.
A presença de enxofre em biodiesel causa problemas ao meio ambiente, ao motor e seus pertences. É importante para assegurar o desempenho e qualidade adequada aos combustíveis. Este trabalho teve como objetivo a realização de uma prospecção tecnológica, visando um mapeamento de Revista GEINTEC
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