Interrupted amperometry: An ultrasensitive technique for diffusion current measuring

Abstract

One of the key aims of electroanalytical methods development is the increase in sensitivity of measurements. This communication reports about a new amperometric technique called “interrupted amperometry” that is based on periodic interruption of the measuring electrical circuit. The main feature of this method is that capacitive current is analytically useful as well as faradaic current. This enables a dramatically higher sensitivity compared to the conventional amperometry. Theoretical consideration of the proposed method as well as the design of the home-made instrumentation is presented. Iron (III) was chosen as a model analyte in this preliminary study in order to demonstrate analytical possibilities of interrupted amperometry. The theoretical limit of detection of iron (III) at a carbon rotating disk electrode was found to be 3nM. The calibration curve is linear in the whole investigated concentration range from 0.02 to 0.38μM and gave a value of 1.22μAμM−1 for the sensitivity. These results were compared with the values obtained in conventional direct-current amperometry mode other conditions being the same: 0.2μM and 0.81nAμM−1 for the limit of detection and sensitivity, respectively. The proposed technique can be useful for titration, flow injection analysis, HPLC, amperometric sensors, potentiostatic coulometry and for amperometric measurements with ultramicroelectrodes.