Determination of copper, iron, nickel and zinc in ethanol fuel by energy dispersive X-ray fluorescence after pre-concentration on chromatography paper

This paper presents an alternative analytical method employing energy dispersive X-ray fluorescence (EDXRF) to determine copper, iron, nickel and zinc ions in ethanol fuel samples after a pre-concentration procedure. Our pre-concentration strategy utilizes analyte retention on cation exchange chromatography paper, a convenient substrate for direct EDXRF measurements. The repeatability, expressed in terms of RSD of standard solutions containing 0.25 μg mL−1 of Cu, Fe, Ni and Zn, and calculated from fifteen consecutive measurements, was 2.5, 2.8, 3.0, and 2.7%, respectively. The limits of detection (LOD), defined as the analyte concentration that gives a response equivalent to three times the standard deviation of the blank (n = 10), were found to be 13, 15, 15 and 12 μg L−1 for Cu, Fe, Ni and Zn, respectively. The proposed method was applied to Cu, Fe, Ni and Zn determination in hydrated ethanol fuel samples collected from different gas stations.

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► A procedure is proposed for analyzing metal ions in ethanol fuel samples by EDXRF after a preconcentration step.
► The preconcentration process involves analyte retention on chromatography paper.
► The method does not require the sample to be subjected to time-consuming pretreatment.