Determination of sulfur compounds in gasoline using mercury film electrode by square wave voltammetry

A sensitive method based on square wave voltammetry is described for the quantitative determination of elemental sulfur, disulfide and mercaptan in gasoline using a mercury film electrode. These sulfur compounds can be quantified by direct dissolution of gasoline in a supporting electrolyte followed by subsequent voltammetric measurement. The supporting electrolyte is 1.4 mol L−1 sodium acetate and 2% acetic acid in methanol. Chemical and optimum operational conditions for the formation of the mercury film were analyzed in this study. The values obtained were a 4.3 μm thickness for the mercury film, a 1000 rpm rotation frequency, −0.9 V applied potential and 600 s depositing time. Voltammetric measurements were obtained using square wave voltammetry with detection limits of the 3.0 × 10−9, 1.6 × 10−7 and 4.9 × 10−7 mol L−1 for elemental sulfur, disulfide and mercaptan, respectively.