A simplified approach to capillary electrophoretic separation of polymerase chain reaction fragments of forensic interest

We report a sensitive and low-cost capillary electrophoretic typing method and its application to a short tandem repeat system widely used in forensic identification (HUMCD4). Separations are carried out with internally coated 100 μm fused-silica capillaries filled with a noncrosslinked gel sieving matrix based on 1.50-1.75 hydroxyethylcellulose. Detection was by laser-induced fluorescence detection. As running buffer, 100 mM Tris-borate with 0.1 mM EDTA, pH 8.7, was used. Samples were simply diluted (≤ 1:10 in water) prior to separation. Both electrokinetic injection and analytical separation were carried out at -180 V/cm. The method enabled separation of HUMCD4 alleles, with fair precision in terms of absolute and relative migration times (R.S.D.s of 0.22% and 0.04%, respectively, in intraday tests). The average accuracy of CD4 fragment sizing was 0.218 base pairs. These results confirmed the high suitability of capillary electrophoresis as a screening method for small-size DNA polymorphisms.