Optimizing separation conditions for polycyclic aromatic hydrocarbons in micellar electrokinetic chromatography

We report the separation of polycyclic aromatic hydrocarbons (PAHs) using 0 .1% poly(ethylene oxide) (PEC) in micellar electrokinetic chromatography (M EKC). In the presence of PEO, adsorption of PAHs on the capillary wall was reduced, leading to better resolution and reproducibility. Effects of tetra pentylammonium iodide (TPAI), dextran sulfate (DS), methanol, and sodium la uryl sulfate (SDS) on the separation of PAHs were elucidated. In terms of r esolution and speed, DS, compared to TPAI, is a better additive for separat ion of PAHs. When using 0.1% PEO solution containing 45% methanol, 50 mM SD S, and 0.02% DS, separation of 10 PAHs containing 2 to 5 benzene rings was accomplished in less than 12 min at 15 kV in a commercial CE system. The me thod has also been tested for separating seven PAHs with high quantum yield s when excited at 325 nm using a He-Cd laser. Unfortunately, separation of the seven PAHs was not achieved and sensitivity diminished under the same c onditions. To optimize sensitivity, resolution and speed, a stepwise techni que in MEKC has been proposed. The seven PAHs were resolved in 35 min at 15 kV when separation was performed in 0.1% PEO solution containing 35 mM SDS , 40% methanol and 0.02% DS for 2 min, and subsequently in 0.1% PEO solutio n containing 20 MM SDS, 50% methanol, and 0.02% DS. (C) 2001 Elsevier Scien ce B.V. All rights reserved.