| Abstract: | s‐Adenosyl‐L ‐methionine (SAMe) is an adenosine analogue with therapeutical activity against affective disorders and liver dysfunctions. It can be oxidized on graphite electrode yielding a strongly adsorbed electroactive oxidation product for which a quinone‐imine structure is proposed. This compound is capable of electrocatalyzing the NADH oxidation at low potentials, lowering the overvoltage by about 300 mV. An amperometric method for NADH determination at +0.1 V (Ag|AgCl|KClsat) is developed using an oxidized‐SAMe‐modified electrode in pH 9. Linear calibration plots were obtained with a detection limit of 2.4 nM. The electrode response time and the relative standard deviation of the slope of the calibration plot for 5 different modified electrodes were 12 s and 5.6% respectively. The catalytic scheme also provides the first method to determine SAMe itself by adsorptive differential pulse voltammetry. The linear range was found to be 42.4–424 nM with a reproducibility of 6.9%. The method was applied to SAMe determination in a pharmaceutical formulation. |
