Enhanced light-emitting diode induced fluorescence detection system with capillary electrophoresis.

An enhanced fluorescence detection system of capillary electrophoresis (CE) was equipped with a concave silver mirror, by which the detection sensitivity of light-emitting diode induced fluorescence (LEDIF) can be increased greatly. The silver concave mirror and the cathode window in photomultiplier tube (PMT) were accurately set face to face at the same axis. When the two labeled tumor markers exactly moved to the center of detection window, the emission from analytes are excitated by LED source. Currently, the analytes may be regarded as a luminescent source point. When the source point exactly moves to the focus of the concave mirror, the emission of the labeled sample was collected effectively, enhanced by convergence and reflected by the concave mirror. Then it was sensitively detected by the PMT. The optical mechanism of enhancing detection sensitivity was explored. A simple comparative test on sensitivity was carried out, which aimed to compare sensitivity of the new detection system with concave mirror to that without concave mirror but the other conditions were kept the same. Two tumor markers labeled with FITC were selected for the test, using the simple LEDIF detect system. The results (LOD, 150 nM for L-Leu and L-Val) showed that the detection sensitivity matched with concave mirror reached more 16 times than the detection method without concave mirror.