Electrode calibration with a microfluidic flow cell for fast-scan cyclic voltammetry

Fast-scan cyclic voltammetry (FSCV) is a common analytical electrochemistry tool used to measure chemical species. It has recently been adapted for measurement of neurotransmitters such as dopamine in awake and behaving animals ( in vivo ). Electrode calibration is an essential step in FSCV to relate observed current to concentration of a chemical species. However, existing methods require multiple components, which reduce the ease of calibrations. To this end, a microfluidic flow cell ( m FC) was developed as a simple device to switch between buffer and buffer with a known concentration of the analyte of interest – in this case dopamine – in a microfluidic Y-channel. The ability to quickly switch solutions yielded electrode calibrations with faster rise times and that were more stable at peak current values. The m FC reduced the number of external electrical components and produced linear calibrations over a range of concentrations. To demonstrate this, an electrode calibrated with the m FC was used in FSCV recordings from a rat during the delivery of food reward – a stimulus that reliably evokes a brief increase in current due to the oxidation of dopamine. Using the linear calibration, dopamine concentrations were determined from the current responses evoked during the behavioral task. The m FC is able to easily and quickly calibrate FSCV electrode responses to chemical species for both in vitro and in vivo experiments.