Development Of An Integrated And Low-cost LED Induced Fluorescence Detector Based On Orthogonal Optical Arrangement

In recent years, microfluidic chip based analysis has made great progress in realizing the lab-on-a-chip concept of integrating all components in analytical system onto a single chip and a series of achievements has been made. Laser-induced fluorescence (LIF) which is one of the main detection techniques in the analytical systems has been paid broad attention during the past few decades. However, lasers which are used as excitation sources in LIF detection system usually suffer from a number of limitations, such as expensive, large size and limited lifetime (～3000 h). As a result, a simple, low-cost, sensitive, and miniaturized light emitting diode induced fluorescence (LED-IF) detector for capillary electrophoresis (CE) using a blue Columnar and Concave with flange light emitting diode (LED) as excitation source and a home-made photodiode as photo-detector is constructed and evaluated.In this work, a miniaturized and low-cost effective LED-IF detection system for capillary eletrophoresis with a simple orthogonal optical arrangement was developed. As means to get better collimating results and reduce the background noise, a small, high-brightness and inexpensive Columnar and Concave with flange LED was used as excitation source for fluorescence detection in this work. A laser lens got from a DVD-ROM was used to focus the laser beam into a spot of～80μm diameter. The fluorescence signal was collected by a biconvex lens got from a pen microscope, and detected by a photodiode in order to miniaturize the system and reduce the cost of the system. The cost of the whole system is less than $ 48. The concentration limit of detection (LOD) for fluorescein was 0.92μM (S/N=3). The utility of this detector was successfully demonstrated by the separation of FITC-labeled L-arginine and D-, L-b-phenylalanine. Due to the use of the orthogonal arrangement, the size of the detector was only 4×13×6 mm~3 (W×L×H). The system has advantages such as simple structure, low cost and ease of integration.