On-line preconcentration and analysis of neutral propiconazole and atrazine in wheat flour by micelle to cyclodextrin stacking-micellar electrokinetic chromatography

Abstract

Online micelle to cyclodextrin stacking (MCDS) was demonstrated to preconcentrate neutral propiconazole enantiomers and atrazine, followed by separation under suppressed EOF MEKC. Stacking occurred at the boundary between SDS micelle-bound analytes and neutral alpha-cyclodextrin (α-CD), where the analytes were released upon formation of inclusion complexes between SDS micelles and α-CD. The SDS concentration in the sample matrix, the ratio of α-CD and sample solution injection time, and the electrokinetic sample injection voltage during MCDS were optimized. The LODs obtained using MCDS-MEKC were 0.12 µg/mL for propiconazole enantiomeric peak 1, 0.096 µg/mL for propiconazole enantiomeric peak 2 and 0.0018 µg/mL for atrazine. When compared with electrokinetic injection (EKI) in MEKC, the sensitivity enhancement factor (SEFs) of MCDS-MEKC were 59 to 79-fold. Linearity was 20-fold (0.34-6.8 µg/mL) for propiconazole and 200-fold (0.022-4.3 µg/mL) for atrazine; an indication that MCDS-MEKC could be applied for both trace and concentrated analyses. The feasibility of MCDS in a complex sample was demonstrated using spiked wheat flour, where the solid sample was only prepared with an organic solvent, redissolved in the micellar diluent and directly analyzed. The MCDS-MEKC showed the potential in simplicity with good online preconcentration ability without utilizing extensive off-line sample treatment.

Keywords: Capillary electrophoresis; Micellar electrokinetic chromatography; Micelle to cyclodextrin stacking; Pesticides; Wheat flour.