DNA sample preparation before testing is a routine process. However, significant human-related risks and errors arise when one works with samples containing a small amount of the target product or with large-volume (more than 5 ml) samples. The only way to eliminate the human factor is to design a fully automatic device. A flow-through chamber or cell, which offer a number of advantages over closed-volume systems, may form the basis of such a device. The results of experiments with a cell modification providing a nucleic acid extraction efficiency above 80 %, which is sufficient for a reliable result of the real-time polymerase chain reaction, are presented. Keywords: DNA, flow-through systems, sample preparation, extraction, purification, concentration.