Fuel Ethanol Samples Research Articles

AVALIAÇÃO ANALÍTICA DE ANALISADOR DE COMBUSTÍVEL COMERCIAL NO CONTROLE DE QUALIDADE DE ETANOL E GASOLINA COMUM

ANALYTICAL EVALUATION OF COMMERCIAL FUEL ANALYZER IN GASOLINE AND ETHANOL FUEL QUALITY CONTROL. Brazilian news media is full of examples about fuels out of the compliances and needs to control fuel quality. This work proposed an analytical validation of a commercial near infrared photometer (Xerloq, Tech Chrom Analytical Instruments, Brazil) able to identify percentage of ethanol in fuels comparing with NBR standards. Four procedures were selected: analysis of ethanol percentage in gasoline type C samples comparing with standard method ABNT 13992; analysis of ethanol percentage in fuel ethanol samples comparing with standard method ABNT 5992; linearity correlation and selectivity of standard solution analysis. Comparisons between the photometer and standards measurements were to determine the accuracy and precision of the device which presented a little variation from the norm (ER < 1.3%, sR < 0.4%). With regard to the test for linearity, Ethanol:water mixtures was analyzed with R-squared larger than 0.999 with RMSEV less than 1%. On selectivity tests, Gasoline:Ethanol:water and Methanol:Ethanol:water mixtures were measured with bias error not exceeding 5% for regulated samples. In conclusion, this fuel analyzer can be used to analyze ethanol content in Brazilian fuels with similar results comparing with classical standard volumetric and glass densimeter analysis and may indicate adulteration gasoline and ethanol samples by anomalous data.

Solid-phase extraction of metal ions from fuel ethanol with a nanostructured adsorbent

This work describes the synthesis and characterization of a new octakis[3-(2,2′-dipyridylamine)propyl]octasilsesquioxane (T8-Pr-DPA), and a study of the metal ion preconcentration in fuel ethanol. Batch and column experiments were conducted to investigate for the removal of heavy metal ions from fuel ethanol. The results showed that the Langmuir allowed to describe the sorption equilibrium data of the metal ions on T8-Pr-DPA in a satisfactory way. The following maximum adsorption capacities (in mmolg−1) were determined: 3.62 for Fe (III), 3.32 for Cr (III), 2.15 for Cu (II), 1.80 for Co (II), 1.62 for Pb (II), 1.32 for Ni (II) and 0.88 for Zn (II). The thermodynamic parameters for the adsorption process such as free energy of adsorption (ΔG), enthalpy of adsorption (ΔH) and entropy of adsorption (ΔS) were calculated. Thermodynamic parameters showed that the system has favorable enthalpic, Gibbs free energy, and entropic values. The sorption–desorption of the metal ions has made possible the development of a preconcentration and determination method of metal ions at trace level in fuel ethanol. The method of quantitative analysis for Fe, Cu, Ni and Zn in fuel ethanol by Flame AAS was validated. Several parameters have been taken into account and evaluated for the validation of method, namely: linearity, limit of detection, limit of quantification, and the relative standard deviation and accuracy. The accuracy of the method was assessed by testing analyte recovery in the fuel ethanol samples.

Assessment of Polyatomic Interferences Elimination Using a Collision Reaction Interface (CRI) for Inorganic Analysis of Fuel Ethanol by ICP-QMS

The effectiveness of a collision-reaction interface (CRI) as instrumental device and the addition of oxygen in the composition of auxiliary gas were evaluated to minimize polyatomic species generated in plasma gas caused by direct introduction of fuel ethanol samples through spray chambers in inductively coupled plasma quadrupole mass spectrometry (ICP-QMS). The oxygen flow-rate was optimized as a compromise among signal counts, signal to background ratio (SBR), and background equivalent concentration (BEC). For 12.5 mL min−1 O2, ethanol samples diluted 20 times were introduced into the plasma and deposits of carbon compounds on the sampler and/or skimmer cones were not observed. The performance of CRI using H2 and He inserted through the sampler or skimmer cones was evaluated. Hydrogen gas added through the skimmer cone was more efficient to reduce blank and BEC values. This strategy was necessary to eliminate spectral interferences caused by 40Ar12C+, 40Ar16O+, 12C16O+, at isotopes 52Cr+, 56Fe+, 28Si+ and 24Mg+, respectively. Using matrix-matching calibration and Y internal standard, the optimized method was applied to the determination of Al, Ba, Co, Cr, Cu, Fe, Mg, Mn, Mo, Na, Ni, Pb, Sb, Si, V, and Zn in fuel ethanol. Accuracy of developed method was checked after addition/recovery tests. Recoveries and RSD (n = 12) for all elements varied within the 78–114% and 0.4–2% ranges, respectively. Limits of detection for all elements obtained by combining CRI and ICP-QMS were always better than 0.80 µg L−1 except for Si at 14 µg L−1.

Evaluation study of different glass electrodes by an interlaboratory comparison for determining the pH of fuel ethanol

This work evaluated different combined glass electrodes by means of an interlaboratory comparison in order to determine the pH of fuel ethanol. Four electrodes with different reference electrode systems (Ag/AgCl or Pt/redox pair), liquid junctions (single or double) and internal filling solutions (aqueous KCl or ethanolic LiCl) were used in comparison with the Orion Ross Sure-flow ® N° 8172 BN electrode, a specific electrode advised by the ASTM D6423 standard. Three fuel ethanol samples with different water contents (0.1, 0.6 and 6.8%, w/w) were analyzed by nine laboratories. The results showed that all the electrodes with aqueous KCl filling solution and single liquid junction, including the Orion ® electrode, presented equivalent results. The sole electrode with ethanolic LiCl filling solution showed pH results lower than the other electrodes, whereas the sole electrode with double liquid junction, showed pH results slightly higher than those with similar filling solution containing single liquid junction. On the other hand, only the latter two electrodes presented acceptable repeatability limit values. The results indicate a need to revise the ASTM D6423 standard with the purpose of enlarging the number of electrodes that can be used to measure the pH of ethanol fuel, as well as support the harmonization of the different regional standards used to measure the pH of fuel ethanol.

New Methodology for pH Measurements in Fuel Ethanol Using Glass Electrode

Abstract Studies carried out with glass electrode in anhydrous ethanol and ethanol-water solutions for measuring pH values have shown that this parameter depends on the solution composition, the contact time with the solution, the utilized temperature, and the type of electrolyte used. It was also observed that the glass electrode behavior in an acid medium differs from an alkaline medium. These studies provided correction factors for pH values from 2 to 12, allowing the realization of proper measurements of the hydrogen ionic activity in the ethanol-water and anhydrous ethanol solutions. However, these correction factors could not be applied to the fuel ethanol. Alternatively, a new method was developed for the correction of the pH values, which can be applied in hydrous and anhydrous fuel ethanol samples.

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

USP, Fac Filosofia Ciencias & Letras Ribeirao Preto, Dept Quim, BR-14040901 Ribeirao Preto, SP, Brazil

A simple electroanalytical method for the analysis of the dye solvent orange 7 in fuel ethanol

The purpose of this paper is to develop a simple, rapid and accurate electroanalytical method for the determination of solvent orange 7 (SO-7), commercially used as a dye marker in fuel ethanol samples. SO-7 is oxidized in a mixture of Britton–Robinson buffer with N,N-dimethylformamide (1:1, v/v) at a glassy carbon electrode and presents a well-defined peak around +0.70 V vs. Ag/AgCl, which can be monitored by linear-scan voltammetry (LSV) and square-wave voltammetry (SWV). Using optimized parameters based on the SWV technique, it is possible to get a linear relationship between the peak current and the SO-7 dye concentration from 4.0 × 10 −6 to 18.0 × 10 −6 mol L −1 ( r = 0.995). The proposed method was successfully applied to the direct quantification of the SO-7 dye in fuel ethanol samples, which gave good average recovery for commercial samples containing 5.0 mg L −1 and 10.0 mg L −1 of SO-7 dye, respectively.

Application of Cellulose Modified with p‐Aminobenzoic Groups in Preconcentration System for Determination of Cu, Fe, Ni, and Zn in Fuel Ethanol Samples by Flame Atomic Absorption Spectrometry

Cellulose chemically modified with p‐aminobenzoic groups, abbreviated as Cel‐PAB, was used for preconcentration of copper, iron, nickel, and zinc from ethanol fuel, normally used in Brazil as engine fuel. The surface characteristics and the surface area of the cellulose were obtained before and after chemical modification using FT‐IR, elemental analysis, and surface area analysis (B.E.T.). The retention and recovery of the analyte elements were studied by applying batch and column techniques.

Electroanalysis and determination of acetaldehyde in fuel ethanol using the reaction with 2,4-dinitrophenylhydrazine

The voltammetric reduction of acetaldehyde was studied in 0.1 M LiOH: LiCl (60: 40 v/v). Well-defined waves can be seen at −1.77 and −1.60 V with the use of hanging mercury and glassy carbon electrodes. Acetaldehyde was shown to react at room temperature with the 2,4-dinitrophenylhydrazine and the product exhibited a differential pulse voltammetric peak at −0.90 V, which was well separated from the peaks of the derivative. This allowed the indirect determination of acetaldehyde in the presence of 0.1 M ethanol/tetrabutylammonium perchlorate after 10 min of reaction. Calibration graphs were obtained for 1.00 × 10−6−1.00 × 10−4 M of acetaldehyde. The detection limit is 8.14 × 10−7 M. The method has been applied satisfactorily to the determination of total aldehyde in fuel ethanol samples without any pretreatment.

Eletroanálise de derivados acetaldeído com hidrazina e determinação em amostras de álcool combustível por voltametria de onda quadrada

A square wave voltammetric method is described for the determination of acetaldehyde using the derivatization reaction with hydrazine sulphate, based on the reduction of hydrazone generated as a product that exhibits a single well-defined peak at -1.19V in acetate buffer at pH 5. Calibration graphs were obtained from 1.0 x 10-6 mol L-1 to 10 x 10-6 mol L-1 of acetaldehyde, using a reaction time of 8 min and a hidrazine concentration of 0.02 mol L-1. The detection limit was 2.38 x 10-7 mol L-1. The method was applied satisfactorily to the determination of total aldehyde in fuel ethanol samples without any pre-treatment.

The development of a method for the determination of trace elements in fuel alcohol by ETV-ICP-MS using isotope dilution calibration

A method for the determination of Ag, Cd, Cu, Pb and Tl in fuel alcohol by isotope dilution electrothermal vaporization inductively coupled plasma mass spectrometry (ID ETV-ICP-MS) is proposed. The analytes were separated in two groups: Ag and Cu were determined without modifier and Cd, Pb and Tl with the use of Pd as chemical modifier. The employed ETV operational conditions were pyrolysis temperature of 800 °C for Cd, Pb and Tl and of 900 °C for Ag and Cu and vaporization temperature of 2400 °C for both groups. Seven common, one with additive and one anhydrous fuel ethanol samples were analyzed. The spiked and reference isotopes were, respectively, 109Ag and 107Ag, 112Cd and 111Cd, 63Cu and 65Cu, 206Pb and 208Pb and 203Tl and 205Tl. The added amounts of the enriched isotope material were the same for all samples: 4.6 ng of 109Ag, 5 ng of 112Cd, 21.1 ng of 63Cu, 9 ng of 206Pb and 0.21 ng of 203Tl. The blank was bi-distilled ethanol, acidified with 0.3% (v/v) nitric acid, as the samples. The limits of detection (LODs) were calculated as three times the standard deviation of the concentrations in the blank ( n = 10) and were, in μg L −1, for Ag: 0.02, for Cd: 0.08, for Cu: 0.1, for Pb: 0.05 and for Tl: 0.001. The obtained concentrations in the samples were in agreement with those obtained by external calibration (EC), according to the paired t-test. The isotope dilution (ID) showed to be a robust, fast and simple calibration technique for the analysis of fuel ethanol.

Rapid and sensitive method for the determination of acetaldehyde in fuel ethanol by high-performance liquid chromatography with UV–Vis detection

A high-performance liquid chromatography (HPLC) method for the determination of acetaldehyde in fuel ethanol was developed. Acetaldehyde was derivatized with 0.900 mL 2,4-dinitrophenylhydrazine (DNPHi) reagent and 50 microL phosphoric acid 1 mol L(-1) at a controlled room temperature of 15 degrees C for 20 min. The separation of acetaldehyde-DNPH (ADNPH) was carried out on a Shimadzu Shim-pack C18 column, using methanol/LiCl((aq)) 1.0 mM (80/20, v/v) as a mobile phase under isocratic elution and UV-Vis detection at 365 nm. The standard curve of ADNPH was linear in the range 3-300 mg L(-1) per injection (20 microL) and the limit of detection (LOD) for acetaldehyde was 2.03 microg L(-1), with a correlation coefficient greater than 0.999 and a precision (relative standard deviation, RSD) of 5.6% (n = 5). Recovery studies were performed by fortifying fuel samples with acetaldehyde at various concentrations and the results were in the range 98.7-102%, with a coefficient of variation (CV) from 0.2% to 7.2%. Several fuel samples collected from various gas stations were analyzed and the method was successfully applied to the analysis of acetaldehyde in fuel ethanol samples.

Determination of total aldehydes in fuel ethanol by MBTH method: sequential injection analysis

A sensitive SIA method was developed for total aldehyde determination in automotive fuel ethanol samples. It was based on the selective reaction of aliphatic aldehydes with 3-methyl-2-benzothiazolone hydrazone (MBTH) with the formation of blue dye in the presence of Fe3+. Monosegmentation and binary sampling were employed to increase the sensitivity of the method. In order accelerate reaction rate of MBTH and aldehyde a mixing coil was inserted into a microwave oven cavity were the sample zone was homogeneously heated. The linear range was 0.3-6 mg L-1 with a precision, expressed as relative standard deviation, lower than 2.5% and detection limit of 60 mug L-1. The method has been successfully applied to the determination of total aldehydes in fuel ethanol and the results agreed with those obtained with 2,4-DNPH-HPLC. In the optimal condition the system can carry out 10 samples per hour.