Separation of the insecticidal pyrethrin esters by capillary electrochromatography

A simple, rapid technique for the direct separation and quantification of t he six insecticidally active pyrethrin esters in typical extracts and comme rcial formulations by capillary electrochromatography (CEC) has been descri bed. The separation of the pyrethrin esters was achieved by optimizing seve ral parameters including the length of stationary phase, the mobile phase c omposition and column temperature. The mobile phase composition had the mos t pronounced effect toward resolving these structurally similar compounds. A ternary mobile phase composed of acetonitrile-aqueous buffer-tetrahydrofu ran (55:35:10) provided the elutropic solvent strength needed to resolve th e six esters from an extract mixture in under 16 min. A 25 cm packed bed or Hypersil 3 mum C-18 stationary phase was used with the ternary mobile phas e at 25 degreesC and 30 kV voltage. These conditions also yielded excellent separation of the pyrethrin esters in two different commercially available insecticidal formulations. In addition, the developed CEC method was shown to be a fast and easy way of quantifying the amount of these esters in typ ical pyrethrin formulations. (C) 2001 Elsevier Science B.V. All rights rese rved.