Separation of methylated isomers of benzo[a]pyrene using micellar electrokinetic chromatography Original Research Article

There is a growing need for developing pseudostationary phases (PSPs) for micellar electrokinetic chromatography (MEKC) capable of resolving very hydrophobic compounds that differ minimally in their structure. Separation of highly hydrophobic compounds (e.g., isomers of methylated benzo[a]pyrene (MBAP)) using MEKC with conventional surfactant such as sodium dodecyl sulfate is very difficult, if not impossible. Recent studies have shown that polymeric surfactant are capable of separating highly hydrophobic compounds. In this report, the use of polymeric surfactant, poly(sodium undecenyl sulfate) (poly-SUS) is described for separations of MBAP isomers. Several parameters were manipulated to provide optimum separation of these isomers. These included buffer pH, acetonitrile (ACN) concentration, poly-SUS concentration, capillary temperature, and effect of a second organic modifier, isopropanol. Optimum MEKC separation conditions were: 35% (v/v) acetonitrile, 7.5 mM sodium borate buffer, pH 12.0, 30 kV with 0.5% (w/v) poly-SUS and 25 °C. These conditions provide separation of 7 of the 12 MBAP isomers within 26 min demonstrating the potential of poly-SUS as a useful PSP for the MEKC separation of highly hydrophobic, geometrical MBAP isomers.