Electrochemical detection of catecholamines at sub-5 fg levels by redox cycling.

Two simple modifications to a commercially available thin layer electrochemical detector cell permitted the attainment of ultra-low detection levels of two neurotransmitter catecholamines. An ESA model 5041 analytical cell was modified with a glassy carbon embedded ceramic composite electrode to allow the use of a thin 12 microm gasket. Also a capillary HPLC column was connected directly to the detector cell using a 30 microm i.d. fused silica capillary. These modifications permitted the extensive redox cycling of the electrochemically reversible catecholamines. The ensuing amplified analytical signal allowed the detector cell to achieve efficiencies of 1300%. This resulted in a mass limit of detection of 4 fg and a concentration limit of detection of 116 pM for dopamine with an S/N of 3.