Capillary isotachophoretic analysis of serum lipoproteins using a carrier ampholyte as spacer ion

We have developed a novel analytical method for serum lipoproteins using a commercially available capillary electrophoresis apparatus, BioFocus 3000 (Bio-Rad Laboratories Co Ltd, USA). The analytical principle is isotachophoresis (ITP), using a carrier ampholyte, BioLyte 7/9, as a spacer ion. The method allows a much higher resolution of lipoproteins than of amino acid mixtures. Serum lipoproteins are normally separated into 13-15 peaks, including some shoulder peaks. The reproducibility of repeated analysis within a day was relatively good with the coefficient of variation within the range 0.9-1.1%. VLDL, LDL and HDL prepared by discontinuous density ultracentrifugation could be further separated by capillary ITP. This high-resolving ability of our method enabled detection of small amounts of abnormal lipoprotein species. For example, small dense LDL, which is thought to be an atherogenic lipoprotein, could be detected within the LDL group peak. Moreover, an abnormal HDL, apolipoprotein E-rich HDL, was also detected by a single analysis. These findings suggest that our capillary ITP method is a useful means for detailed analysis of lipoproteins and thus for clinical diagnosis of hyperlipoproteinaemic subjects.