IMPROVED DETECTION LIMIT FOR CATECHOLAMINES USING LIQUID-CHROMATOGRAPHY ELECTROCHEMISTRY WITH A CARBON INTERDIGITATED ARRAY MICROELECTRODE

The detection limit of catecholamines can be lowered by using a carbon -based interdigitated array (IDA) microelectrode as a detector for liq uid chromatography (LC). The IDA electrode is more sensitive than conv entional glassy carbon electrodes due to the high current density caus ed by radial diffusion at each microband, and redox cycling between tw o microband arrays. Since the number of redox cycles increases at lowe r flow-rates, the carbon IDA is particularly useful for microbore LC. In an LC system with a l-mm microbore column and a carbon IDA electrod e, the peak height of dopamine (DA) and DOPAC did not decrease with de creasing flow-rate because of this redox cycling. A low detection limi t of 5 fg (32 amol) and 9.6 fg (57 amol) was obtained for DA and DOPAC due to the high current density and low background noise level (0.1 p A) at the carbon IDA electrode. The total charge generated by oxidizin g DA at the anodic array was more than the value calculated by assumin g that all the DA molecules were oxidized.