Indirect detection of amino-substituted polycyclic aromatic hydrocarbons in cyclodextrin-modified micellar electrokinetic chromatography combined with diode laser-induced fluorometry

Indirect fluorescence detection in cyclodextrin (CD)-modified micellar electrokinetic chromatography (MEKC) was demonstrated by using a diode laser as an excitation source. Amino-substituted polycyclic aromatic hydrocarbons (PAHs), which have no absorption band in the deep-red region, were used as model compounds since it was difficult to separate them by conventional MEKC. In the preliminary study, the separation of amino-substituted PAHs was achieved using γ-CD as a modifier. The fluorescence intensity of the visualizing reagent, oxazine 750, increased in the presence of γ-CD due to the complex formation of oxazine 750 with γ-CD. Consequently, the peak areas of amino-substituted PAHs were observed to decrease with increasing concentration of γ-CD. Detection limits were improved due to the enhancement in efficiency and dynamic reserve by adding small amounts of γ-CD. The results obtained in this study were in good agreement with the proposed model.