Quantitative assay of copper, iron, nickel, and zinc in fuel ethanol samples by flame atomic absorption spectrometry

Abstract

After several petroleum crises in the 70's and 80's successive increases in petroleum barrel prices stimulated worldwide research and development of alternative fuels relative to fossil fuels. In this context, fuel ethanol obtained from sugarcane has been successfully applied as an important automotive fuel used in large scale in Brazil, in the pure form or as an addictive for gasoline, thus contributing economic and environmental advantages.Due to its use as an alternative automotive fuel or raw material for the alcohol-chemical industry, the identification and control of organic and inorganic contaminants is necessary because of the possibility of engine corrosion effects or passivation of industrial catalyzers [1]. Several organic[1-4] and inorganic[5-13] contaminants have been studied in fuel ethanol by different instrumental methods. In this case, different sources of contamination can be cited, such as during the production stage (micronutrients and fermentation processes), and during transport and storage of this fuel in metallic containers. The analysis of metallic species in this kind of matrix is of special interest due to its potential for environmental pollution when emitted during the combustion process and its contribution to corrosion effects in motors. Nowadays, Brazilian official methods for analysis of metallic species consist of dosage of sodium[14], copper[15], and iron[16] by using photometric and spectrometric methodologies proposed by the Brazilian Association of Technical Norms (ABNT).According to the literature, the determination of metallic species in fuel ethanol has been carried out using mainly spectrometric [5-11] and voltammetric[12-13] methods.When trace analysis is necessary, the preconcentration of analyte species before the determination step is often required. Voltammetric methods employing an anodic stripping step and using mercury electrodes (film or drop) can provide a preconcentration of analyte at the surface electrode by application of a specific potential during a selected preconcentration time, allowing to detection limits from 10 -9 until 10 -8 mol L -1 for several metallic species [12,13]. However, this technique is limited to a small number of metallic species for direct analysis. Iron and Nickel, for example, require addition of specific chemical reagents and need other technique (adsorptive stripping) or specific chemically modified working electrodes. ____________________________________________________________________________________________________

Determination of mercury in ethanol biofuel by photochemical vapor generation

“…9) recommend the use of atomic spectrometric techniques. Several published articles describe analytical methodologies for the determination of metals in ethanol biofuel using atomic absorption spectrometry 5,6,[10][11][12][13][14] or inductively coupled plasma mass spectrometry. 15,16 Mercury, due to its high volatility and toxicity, is regarded as a harmful air pollutant by the Environmental Protection Agency (EPA), suspected of causing serious damage to health.…”

A new high-performance chelation ion chromatographic system for the direct determination of trace transition metals in fuel ethanol

“…The LOD's were similar or lower than those observed by other authors. 2,9,11,35,36 Table 3 also details the optimum linear response range for each metal ion, with each analyte showing good linearity.…”

“…The LOD's were similar or lower than those observed by other authors. 2,9,11,35,36 In order to determine the precision of the method, four replicate analysis of an ethanolic standard solution were performed. The percent relative standard deviations (%RSD) for all metals were within the range 3 to 3.6% (Table 3).…”

“…8,9 The analytical methods described in the literature for the determination of metal contaminants in fuel ethanol were developed mainly by Brazilian research groups and are generally based on using spectroscopic or electrochemical techniques. 8,[10][11][12] The use of ion chromatography for the separation of metal ions and their species has not been reported for the multielement analysis of fuel ethanol.…”

Determinação de manganês em etanol combustível por voltametria de redissolução

“…A determinação de manganês realizada em um espectrofotômetro de absorção atômica com chama foi baseado na literatura [49].…”