Electrocatalytic determination of hydroquinone with Mn+ modified gold-5-amino-2-mercaptobenzimidazole self-assembled monolayer electrodes

Application of immobilized metal cations on the topside of gold-5-amino-2-mercaptobenzimidazole self-assembled monolayer (Au-5A2MBI-Mⁿ⁺ SAM, Mⁿ⁺:Cu²⁺ or Ag⁺) for electrocatalytic determination of hydroquinone (H₂Q) is described by voltammetric method. Several parameters were investigated to evaluate the performance of the sensors. Calibration curves for H₂Q concentrations were linear from 1.0 × 10^-5 to 4.0 × 10^-4 M (r = 0.998) for Au-5A2MBI, from 1.0 × 10^-5 to 6.0 × 10^-4 M (r = 0.998) for Au-5A2MBI-Cu²⁺, and from 2.0 × 10^-6 to 2.0 × 10^-5 M (r = 0.996) and 1.0 × 10^-4 to 1.0 × 10^-3 M (r = 0.991) for Au-5A2MBI-Ag⁺ SAM modified electrode. The respective detection limits were found as 6.5 × 10^-6, 4.6 × 10^-6 and 1.8 × 10^-7 M. Both Cu²⁺ and Ag⁺ ions were found to have a good electrocatalytic effect on the oxidation of H₂Q; however, Ag⁺ was a more effective catalyst and showed better sensitivity and lower detection limit than all other tested electrodes. Au-5A2MBI-Ag⁺ SAM electrode was used as a suitable sensor for determination of H₂Q in a radiolysis developing agent as real sample. The results obtained by using proposed sensor and that obtained by an ASTM reference method were in good agreement at the 95% confidence level.