Carbon film-based interdigitated ring array electrodes as detectors in radial flow cells

We have fabricated the first carbon film-based interdigitated ring array (IDRA) electrodes for application as detectors in thin-layer radial now cells. The limiting current of dopamine (DA) at the electrode is proportional to the one-third power of the volume now rate (upsilon(1/3)) when two electrodes in the IDRA are held at 750 and 50 mV, respectively. In contrast, it is not proportional to upsilon(1/3) when only one electrode is held at 750 mV with the other electrode disconnected, due to the high conversion of DA in the now cell at a low now rate, The collection efficiency (CE) and redox cycles (Rc) increase with decreasing now rate, since the redox cycling of the IDRA suffers less influence from the now. The IDRA electrode was used in combination with microbore liquid chromatography (LC) for catecholamine detection. The CE and Re are particularly high in the usual now rate range for microbore LC, which is from 0.02 to 0.1 mL/min. Re values of 4.3 and 3.2 were achieved for DA and epinephrine, respectively, at a now rate of 0.02 mL/min, and the noise level of the electrode is low. This indicates that the IDRA electrode is very useful as a highly sensitive electrochemical detector in a radial now cell.