Determination of cationic neurotransmitters and metabolites in brain homogenates by microchip electrophoresis and carbon nanotube-modified amperometry.

An electrophoretic method for simultaneous determination of catecholamines and their O-methoxylated metabolites on the microchip as well as in the capillary is presented. A complex separation system employing sodium dodecyl sulfate (SDS) micelles, dendrimers forming a second pseudostationary phase and borate complexation is needed for the satisfactory separation of the selected compounds on the short migration length. A carbon nanotube-modified working electrode has been applied for the sensitive amperometric detection with submicromolar detection limits. The applicability of this new method for the analytics of real samples is demonstrated by analysis of mouse brain homogenate on the microchip and human urine by capillary electrophoresis.