Analysis of amino acid neurotransmitters by capillary electrophoresis and laser-induced fluorescence using a new fluorescein-derived label

• DOI: 10.1007/s00604-006-0723-6
• Publication Date: 2007-02-07T22:52:07Z
• Authors: Liwei Cao; Huashan Zhang; Wang Hong
• Keywords: Boric acid; Sodium acetate; Buffer solution

A capillary electrophoresis laser-induced fluorescence detection method (CE-LIF) was developed for the separation of eight neurotransmitters tagged on their amino function with 6-oxy-(N-succinimidyl acetate)-9-(2′-methoxycarbonyl) fluorescein (SAMF), a new fluorescent reagent synthesized in our lab. Derivatization was performed in boric acid buffer (pH = 7.75) at 37 °C over 15 min. The pH-independent fluorescence of SAMF (pH 4–9) permits background buffers over a wide range of pH. It was demonstrated that an acidic running buffer offers a better resolution compared to basic medium in terms of resolution and peak shapes. Employing Cu2+ as the additive, the molecules were baseline-separated using a running buffer consisting of 40 mM sodium acetate and 2 mM Cu2+ (pH 6.0). The detection limits ranged from 1 to 2 × 10−10 M. The method has been validated for the characterization of lymphocyte samples. The results obtained illustrate the advantages of combining SAMF derivatization with CE-LIF for determining neurotransmitters.