Adsorption of methimazole on the mercury electrode

The electrosorption behaviour of methimazole (vetranal) at the mercury/1 M NaClO4 interface was determined from a double layer differential capacity measurements extrapolated to zero frequency. Methimazole is the thiourea derivative, which is used as a drug in the overactivity of the thyroid gland. The values of zero charge potential were shifted to negative potentials ca. 230 mV with an increasing methimazole concentration from 10−4 M to 10−1 M. The relative surface excesses Γ′ of methimazole were calculated from surface pressure at the density of surface charge σ = constant. The values of Γ′ increase with the increase of σ. Adsorption of methimazole was analyzed on the basis of the constants obtained from the Frumkin and virial isotherms. The values of the standard Gibbs energy of adsorption ΔG° increase with the increase of σ while the values of interaction parameters A and B decrease.