Amperometric detection of methanol with a methanol dehydrogenase modified electrode sensor

An amperometric enzyme electrode was developed by immobilizing the quinoprotein methanol dehydrogenase from Methylobacterium extorquens AM1 onto a glassy carbon electrode. Ferrocene (FC), ferrocene carboxylic acid, N,N,N′,N′-tetramethyl-1,4-phenylenediamine (TMPD), N,N-dimethyl-p-phenylenediamine (DMPD), phenazine methosulfate (PMeS) and Wurster blue (WB) were evaluated as electron-transfer mediators. DMPD, TMPD and Fc were found to be effective electron-transfer mediators for the enzyme with only ferrocene exhibiting a stable response in the presence of oxygen. The best response for the detection of methanol was achieved with a 100 μM suspension of ferrocene in 100 mM Tris/HCl buffer pH 9.0. The sensor utilized very small quantities of enzyme, and exhibited excellent reproducibility and stability with a detection limit of 0.5 μM (S/N = 3) and a linear range of 0.5–200 μM.