A fast scan cyclic voltammetric digital circuit with precise ohmic drop compensation by online measuring solution resistance and its biosensing application

Abstract

In this work, a novel fast scan digital circuit for voltammetric analysis with precious ohmic drop compensation is developed, which is achieved through online measuring solution resistance first and then proportionally feedbacking the output signal to potentiostat's in-phase input through a potentiometer. It mainly consists of a solution resistance measurement module based on AD5933 chip, an ohmic drop automatic compensation module and a STM32F103ZET6 microcontroller. The performance of the circuit is checked successively using pure resistances, RC dummy cells, RC dummy cells incorporating a pseudo-faradaic component, and the ferrocene redox system. Results show that, precise ohmic drop compensation can be realized online and automatically, affording fast scan cyclic voltammetric (FSCV) analysis for theoretical electrochemical cells at 2000 V/s and that for practical electrochemical system using conventional electrodes at 1600 V/s. Based on this circuit, a very simple DNA biosensor for ultrasensitive detection of mercuric ions was explored. Benefitting from the high sensitivity brought by the high scan rate, the limit of quantitation (LOQ) can reach 1 pmol/L, demonstrating the application potential of FSCV in the field of ultrasensitive electrochemical detection.