Capillary electrophoresis of serum proteins. Reproducibility, comparison with agarose gel electrophoresis and a review of the literature.

Abstract

Conditions of serum protein analysis by capillary electrophoresis were optimized and within day, between day and between capillary variations were examined for both migration times and relative peak areas. For the five currently accepted zones, albumin, alpha 1, alpha 2, beta and gamma-globulin, reproducibilities of migration times were in the range of 2.3-3.1% (n = 200 measurements). Although variations in relative peak areas were slightly higher than those obtained by conventional agarose gel electrophoresis, from a resolution perspective, capillary electropherograms provided better detail than the densitometric scans of agarose gel electrophoresis. Precise localization of C3 and transferrin in capillary electrophoresis resulted in more accurate detection of the beta-globulin fraction. When C3 appeared in the gamma-fraction it was not detected as a separate peak in agarose gel electrophoresis, whereas it was in capillary electrophoresis. In artificially prepared mixtures of highly purified albumin and gamma-globulin preparations, best correspondence with theoretical values was found with capillary electrophoresis. Inter-individual variations and reference values were obtained by measuring 140 samples from healthy controls (59 females, 81 males) with both techniques. For capillary electrophoresis the inter-individual variations of the albumin, alpha 1, alpha 2, beta and gamma fractions were respectively 6, 21, 19, 14 and 18% and for agarose gel electrophoresis 5, 20, 17, 18 and 22%. From these results it can be concluded that the more precise localization of the beta- and gamma-globulin fraction results in about 4% lower inter-individual variations in capillary electrophoresis compared to agarose gel electrophoresis. For the other fractions, comparable variations were obtained. Differences between males and females were not significant. For patient samples, a good correlation was found between capillary electrophoresis and agarose gel electrophoresis data for all five protein fractions. We conclude that separation efficiency of capillary electrophoresis is better than that of agarose gel electrophoresis and even weak monoclonal components can easily be distinguished with the capillary electropherogram. Capillary electrophoresis is a qualitatively good, cheap, fast and easy to perform alternative to agarose gel electrophoresis.