Application of a novel micro-injector in the determination of indole derivatives in the rat pineal gland by capillary electrophoresis with electrochemical detection

A novel micro-injector has been fabricated for capillary electrophoresis (CE). It was successfully used for the determination of some indole derivatives for example melatonin (MT), serotonin (5-HT), tryptophan (Tip), and 5-hydroxy-tryptophane (5-HTrp) in the rat pineal gland by capillary electrophoresis with electrochemical detection (CE-EC). CE was performed in 0.20 mol L-1 phosphate buffer (pH 8.0). The compounds investigated can be well separated and detected within 15 min. The working electrode used was a 300-mum diameter carbon electrode positioned opposite the outlet of the capillary. The relationship between peak current and analyte concentration was highly linear in the range from 0.10 to 500 mu mol L-1; detection limits (S/N = 3) were 0.03-0.13 mu mol L-1. The proposed method has been successfully used to analyze real biological samples.