DETERMINATION OF PEPTIDES BY CAPILLARY ELECTROPHORESIS ELECTROCHEMICAL DETECTION USING ON-COLUMN CU(II) COMPLEXATION

A Cu(II)-coated capillary has been developed for the determination of peptides by capillary electrophoresis with electrochemical detection. Capillaries were prepared by forcing a solution 48 mu M in CuSO4, 120 mu M in tartaric acid, 2.4 mM in NaOH and 120 mu M in KI through them for 25 min; the resulting capillaries are stable for at least 12 h. Un der alkaline conditions, peptides complex with Cu(II) present on the w alls of the capillary to form Cu(II)-peptide complexes which can be de tected oxidatively at a carbon fiber electrode. Di-, tri-, tetra- and pentaglycine were determined with a detection limit of 7.10(-7) M for triglycine. N-Terminal-blocked peptides can also be determined via thi s method. This system is more sensitive than direct detection of pepti des by UV at 210 nm and exhibits higher selectivity than commonly empl oyed derivatization procedures based on reactions with a primary amine functionality.