Separation of natural pyrethrum extracts using micellar electrokinetic chromatography

The separation of the six pyrethrin eaters in a technical pyrethrum extract (Riedel-de-Haen, Cresent Chemical Co. Inc. Hauppauge, NY, USA) by micellar electrokinetic chromatography (MEKC) using both sodium dodecyl sulfate (SD S) and a polymerized surfactant as pseudo-stationary phases has been invest igated and optimized. Parameters such as pH, SDS and polymerized sodium N-u ndecyl sulfate (poly-SUS) concentration, type and concentration of backgrou nd electrolyte and organic modifier, as well as the acetonitrile/water rati o in the sample were studied, to optimize the resolution, efficiency, and a nalysis time. An optimized separation of the six pyrethrin esters was achie ved in 25 min with 25 mM Tris, buffered at pH 9, containing 30 mM SDS, 25% (v/v) acetonitrile, and an equal volume ratio of acetonitrile/water sample matrix at a voltage of 25 kV. The use of 0.5% (w/v) poly-SUS enhanced resol ution of the pyrethrin esters and shortened the total analysis time from 25 to 20 min, compared to the SDS mediated separation. The optimized MEKC res ults are compared to the HPLC separation of these eaters and show an improv ement in efficiency and total analysis time. (C) 1999 Elsevier Science BN. All rights reserved.