Effect of surface-active agents on amperometric NADH measurements with chemically modified electrodes

A special electrochemical pretreatment was employed in the case of finely polished glassy carbon electrode surfaces to increase the adsorption of the redox mediator Meldola blue (7-dimethylamino-1,2-benzophenoxazine). The chemically modified glassy carbon electrode holding the adsorptive mediator layer was used to measure the NADH concentration amperometrically. The interfering effect of non-ionic surfactants was studied for NADH measurements using a rotating disc electrode technique and flow injection measurements. The glassy carbon electrode response was less affected and could be regenerated much more easily than the response of a similar spectrographic graphite based electrode, studied earlier. Surface active agents can influence the apparent coverage of the surface by the mediator.