The capillary electrophoresis (CE)-laser-induced fluorescent (LIF) method with 5-FAM SE (5-Carboxyfluorescein N-succinimidyl ester) derivatization for the analysis of serotonin can be used to quantify luminally released 5-HT with high sensitivity. CFSE is an excellent dye for the derivatization of 5-HT. 5-FAM SE (5-Carboxyfluorescein succinimidyl ester) is chosen as the labeling reagent to precapillary derivatize the two marker aminohydroxyphenylalanine (AHP) isomers produced after reductive hydrolysis of pheomelanin with hydriodic acid (HI).