In genetic analysis by capillary electrophoresis with polymer solutions there are many variables that affect separation of the DNA fragments. A very critical one is the sample injection process, which can considerably affect the peak efficiency and the resolution. In this work, we have studied the influence of the DNA sample composition and the electrokinetic injection conditions in the separation of DNA fragments by capillary electrophoresis using replaceable polymer solutions. The studies were carried out by electrokinetically injecting the DNA samples under a variety of conditions, such as sample ionic strength, buffering capacity and the quality of the separation matrix. In all experiments DNA was stained with ethidium bromide for laser-induced fluorescence (LIF) detection and separated in a poly(vinylalcohol) coated capillary column filled with 0.5% hydroxyethylcellulose solution under a 200 V cm-1 electric field. Under such conditions, samples prepared with 1 to 5 mmol L-1 of running buffer have been shown to produce reproducible injections with RSD < 4% for both migration time and peak area.
DNA sizing; polymer solutions; electrokinetic injection; laser-induced fluorescence
