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 mu m gasket. Also a capillary HPLC column was connected directly to the detector cell using a 30 mu m 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. (C) 1999 Elsevier Science B.V. All rights reserved.