Analytical separations with polyelectrolyte layers, molecular micelles, or zwitterionic polymers

Abstract

Polymeric surfactants (molecular micelles) are disclosed for use in open tubular capillary electrochromatography or in high performance liquid chromatography. For example, fused silica capillaries are coated with thin films of charged polymers in a polyelectrolyte multilayer (PEM). A PEM coating may be formed in situ by alternate rinses with positive and negative polyelectrolytes. At least the innermost of the negatively charged polymer layers is a molecular micelle. Prototype embodiments have successfully separated seven benzodiazepines from one another. The run-to-run, day-to-day, week-to-week and capillary-to-capillary reproducibilities were very good, with relative standard deviation values less than 0.01. The PEM-coated capillary was very robust over at least 200 runs. Stability against high and low pH values was also observed. Using chiral polymerized micelles, chiral separations may be achieved, as was demonstrated with a separation of the enantiomers of 1,1'-binaphthyl-2,2′-dihydrogenphosphate. Alternatively, layers for use in this invention may be formed from zwitterionic polymers in lieu of separate cationic and anionic layers. Zwitterionic polymer layers may be used either with or without molecular micelles.