Voltammetric determination of sulfur-containing substances in motor fuels using bismuth-modified screen-printed carbon electrodes

An electrochemical method for the determination of sulfur-containing compounds in motor fuels using square-wave voltammetrys developed. The relevance of the research is driven by increasingly stringent environmental regulations governing sulfur content in gasoline and diesel fuels in accordance with the Euro 5 and Euro 6 standards. Carbon-based electrodes fabricated by screen-printing on a dielectric substrate and modified with a bismuth film were employed as sensing elements. The use of such electrodes ensures environmental safety and high reproducibility of analytical characteristics. The conditions for bismuth electrodeposition used to modify the voltammetric sensor were optimized by means of cyclic voltammetry and electrochemical impedance spectroscopy. Model solutions of dibutyl sulfide were used plotting the calibration curve. It has been shown that preliminary accumulation of the analyte for 60 sec increases the sensitivity of determination by 30%. The detection limit calculated according to the 3σ-criterion was 0.05 mg/L, relative standard deviation did not exceed 10%. The developed technique has been tested in the analysis of real samples of gasoline with different octane ratings and diesel fuel. The obtained sulfur contents allowed as to classify all the samples as Euro 5 class. A comparison of the obtained results with those derived from potentiometric titration and X-ray fluorescence analysis according to ASTM D2622 showed good agreement. The developed electrochemical technique can be used for rapid and reliable quality control of motor fuels in both production and analytical laboratory environments.

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