Enhanced detection of trace sulfur levels in gasoline by bismuth electrode using square wave voltammetry

This study introduces a simple, cost-effective, and rapid bismuth electrode-square-wave voltammetry method for determining the total sulfur content in automotive gasoline. Optimal conditions for the developed electrode, including various Bi ion concentrations, deposition times, and potentials, were established on a glassy carbon electrode. The results demonstrated that the highest response was achieved when the bismuth electrode was placed in an acetate buffer and a methanol:toluene (1:1 v/v) solvent. The method was validated with and without a 30-second electro-preconcentration step. The voltammetric method in conjunction with the preconcentration step exhibited a sensitivity of 571.81 nA mg L⁻¹, a limit of detection (LOD) of 0.02 mg L⁻¹, and a limit of quantification (LOQ) of 0.08 mg L⁻¹. Without the preconcentration step, the method yielded a sensitivity of 421.89 nA mg L⁻¹, an LOD of 0.03 mg L⁻¹, and an LOQ of 0.11 mg L⁻¹. The developed method was applied to quantify commercial fuel samples. The results showed that the electrochemical technique yielded a similar total sulfur content to that measured by the standard ASTM D2622 method, with an error of less than 7.5%. Moreover, the method proposed in this study had lower LOD and LOQ limits, meeting the EURO5 and EURO6 regulations.