The special effect of fluoride as a Lewis base additive in suppressing the ligand-exchange inter-actions for acidic analytes on polybutadiene-coated zirconia (PBD-ZrO2) has been investigated. We found that fluoride is more effective than phosphate in improving the separation efficiency for strong acids. The improvement is attributed to that fluoride has a smaller size and a more flexible coordination chemistry towards zirconium centers than phosphate; consequently, fluoride can more effectively improve the kinetics of the ligand-exchange processes for strongly acidic analytes. We demonstrated that using a small amount of fluoride in combination with a larger quantity of phosphate is a practical way to improve the separation efficiency and resolution for acidic analytes. Some example separations are presented.
- Acidic analytes
- Column liquid chromatography
- Fluoride eluent
- Ligand-exchange interaction
- Polybutadiene - coated zirconia