Detection limit of DNA analyzer

The sensitivity of the DNA analyzer, which was designed by authors group to detect the samples of capillary electrophoresis (CE) with Laser induced fluorescence (LIF), was analyzed in theory and experiment. The detection sensitivity of fluorescence depends on both the fluorescent intensity entering the sensors (PMT or CCD) and the performance of sensors. Given an actual DNA analyzer, the calculated detection limit of TO (thiazole orange) fluorophore was 0.1271-0.1272 fluors per cubic micron. The experimental result of CE about double-stranded (ds) TO probes (the standard sample pGEM-3Zf(+)/Hae III Markers) is 0.1454 fluors per cubic micron. The study shows that the approaches for improving detection limit are to make the good coating on inner walls of capillary, choose the suitable sieving matrix, enlarge laser power, increase numerical aperture of objective as much as possible and raise the detection lower limit of photomultiplier.