Optimization of separation and migration behavior of chloropyridines in micellar electrokinetic chromatography

The separation and migration behavior of pyridine and eight chloropyridines , including three monochloropyridines, four dichloropyridines, and 2,3,5-tr ichloropyridine were investigated by micellar electrokinetic chromatography using either sodium dodecyl sulfate (SDS) as an anionic surfactant or SDS- Brij 35 mixed micelles. Various parameters such as buffer pH, SDS concentra tion, Brij 35 concentration and methanol content that affect the separation were optimized. Complete separation of these chloropyridines was optimally achieved with a phosphate buffer containing SDS (30 mM) and methanol (10%, v/v) at pH 7.0. The resolution and selectivity of analytes could be consid erably affected by the addition of methanol and/or Brij 35 to the backgroun d electrolyte. The migration order of these chloropyridines depends primari ly on their hydrophobicity. However, electrostatic interactions may also pl ay a significant role in the determination of the migration order of the po sitional isomers of chloropyridines. (C) 2001 Elsevier Science B.V. All rig hts reserved.