Line laser beam based laser-induced fluorescence detection system for microfluidic chip electrophoresis analysis

In this work, a new laser-induced fluorescence (LIF) detection system based on a line laser beam for microfluidic chip electrophoresis analysis was developed. This detection system had the advantages of simple optical structure, compactness, and ease in constructing. Highly sensitive detection was realized by detecting the fluorescence light emitted in the micro-channel through the vertical intersection between the line laser source and micro-channel. The filtered line source was established by a bevel laser beam and a micro-gap which could facilitate the alignment of line laser beam with the microfluidic channel. Both the theoretical analysis and experimental study demonstrated that the detection system with a 0.07 mm-width micro-gap had enough sensitivity and adequate separation efficiency. By this system, a detection limit (S/N > 12) of 1.284 × 10 −10 M fluorescein isothiocyanate was obtained, and the plate number could reach to 6100, which were comparable to those of optimized confocal or orthogonal LIF systems for microchip based capillary electrophoresis. The reproductibility of the detection system was evaluated by Sybr Green labeled DNA markers contained five fragments. Finally, the multi-PCR products including 165 bp, 266 bp, 378 bp and 881 bp fragments could be successfully achieved for baseline separation by this system within 4 min. The work undertaken can gear toward a semi-automated handheld system with substantial time and cost saving.