Highly sensitive fluorescence detection with Hg-lamp and photon counter in microchip capillary electrophoresis Original Research Article

A microchip capillary electrophoresis system with highly sensitive fluorescence detection is reported. The system was successfully constructed using an inverted fluorescence microscope, a highly sensitive photon counter, a photomultiplier tube (PMT) and a capillary electrophoresis microchip. This system can be applied to the fluorescence detection with various wavelengths (300–600 nm). Different fluorescence reagents require different excitation wavelengths. The wavelengths of UV light (300–385 nm), blue light (450–480 nm) and green light (530–550 nm) are employed to excite Titan yellow, fluorescence-5-isothiocyanate (FITC) and Rhodamine 6G, respectively. The detection limit (S/N = 3) of FITC is 7 × 10−10 M, which is 2–3 orders of magnitude lower than that obtained with the lamp-based fluorescence and PMT detection system and approaches the data gained by the laser-induced fluorescence detection. The linear relationship is excellent within the range of concentration 1.3 × 10−9 to 6.5 × 10−8 M FITC. It offers a new method to widen the application of the lamp-based fluorescence detection.