Determination of Catecholamines and Related Compounds by Capillary Electrophoresis with Postcolumn Terbium Complexation and Sensitized Luminescence Detection

A method has been developed for the determination of catecholamines and related compounds (DA, E, NE, DOPA, DOPAC, DOPAG) in urine samples. The compounds of interest were separated by capillary electrophoresis with a borate buffer as background electrolyte. Detection was based on the sensitized luminescence of terbium ions. Using a homemade postcolumn reactor, a basic solution containing a stoichiometric mixture of terbium(III) chloride and EDTA was added postcolumn to the separation buffer. The ternary catechol-EDTA-terbium complexes formed in the reaction mixture showed a strong luminescence with excitation and emission maxima at 300 and 545 nm, respectively. By optimization of the experimental conditions, zone broadening could be restrained and plate numbers up to 130,000 appeared to be possible. Detection limits found were in the order of 10(-7) mol L-1. The catecholic compounds could be determined in urine samples after a standard cleanup and preconcentration procedure.