Abstract

The development of a method based on extraction induced by emulsion breaking (EIEB) aiming copper determination in gasohol using graphite furnace atomic absorption spectrometry (GF AAS) is reported. Emulsification of the gasohol samples was carried out using nitric acid solution, (1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol surfactant (Triton X-114), and ultrasound energy. The variables related to the extraction efficiency were optimized by multivariate approaches (two-level factorial fractional design and Doehlert design). The best results were obtained when the emulsion was formed with 5.0 mL of the sample, 0.200 mL of 2.4 mol L-1 HNO3, 0.100 mL of 10% Triton X-114 and 10 min of sonication. A fast and efficient emulsion breaking was performed at 90 oC. A volume of 6.65 mL of the copper-rich hydroalcoholic phase was extracted, separated from the organic phase and analyzed. Under these conditions, the following analytical characteristics were obtained: 0.61 and 2.0 µg L-1 for limits of detection and quantification, respectively; precision (percentage of relative standard deviation, 10 µg L-1) of 2.8%; and analytical sensitivity of 0.011 L µg -1. Accuracy was assessed by spike tests, and values in the range of 95-110% were achieved. The method was applied in the determination of copper in Brazilian gasoline samples (gasohol with 27% ethanol).

Highlights

  • Gasohol is the second most-consumed automotive fuel in Brazil, second only to diesel

  • In more recent work,[13] determination of Cu, Fe, and Pb in gasohol was proposed applying extraction induced by emulsion breaking for quantification by high-resolution continuous-source flame atomic absorption spectrometry (HR-CS F AAS)

  • Two-level fractional factorial design 24-1 used in the screening of variables involved in the copper extraction induced by emulsion breaking: levels established for the studied variables

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Summary

Introduction

Gasohol is the second most-consumed automotive fuel in Brazil, second only to diesel. Even with all the advantages presented in the methods for determining metals in gasoline, there are few studies that describe the possibility of applying an external calibration.

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