The suitability of noncovalently bilayer-coated capillaries for the analysis of
proteins by capillary electrophoresis (CE) at medium pH was investigated. Fused-
silica capillaries were coated simply by successively
flushing with a
polybrene (PB) and a poly(vinyl sulfonate) (PVS)
solution. A
protein test mixture was used to evaluate the performance of the coated capillaries. Comparisons with bare fused-
silica capillaries were made. Several background
electrolytes (BGEs) were tested in combination with the PB-PVS coating, showing that optimum performance was obtained for the
proteins using high BGE concentrations. With
a 300 mM Tris
phosphate buffer (pH 7.0), good plate numbers (150,000-300,000), symmetrical peaks, and favorable migration-time repeatabilities (RSDs below 0.8%) were obtained for the
proteins. Using bare fused-
silica capillaries, the
protein peaks were significantly broadened and the migration-time RSDs often exceeded 5%. It is concluded that the PB-PVS coating effectively minimizes adverse
protein adsorption and provides a very stable electroosmotic flow (EOF). We also investigated the potential of a commercially available bilayer coating (CEofix) for
protein analysis. It is demonstrated that with this coating, good plate numbers and peak symmetries for
proteins can be achieved when the CEofix BGE ("accelerator") is replaced by a common BGE such as
sodium or Tris
phosphate. Apparently, the negatively charged
polymer present in the "accelerator" interacts with the
proteins causing band broadening. The utility of the bilayer coatings is further illustrated by the separation of
proteins such as
interferon-alpha 2b,
myoglobin and
carbonic anhydrase, by the analysis of a degraded
insulin sample in time, and by the profiling of the
glycoprotein ovalbumin. In addition, it is demonstrated that even in the presence of concentrations of
human serum albumin in the sample of up to 60 mg/mL, the PB-PVS coating still provides reproducible
protein separations of good performance.