A high-sensitivity LIF detector with silver mirror coating detection window and small-angle optical deflection from collinear system for CE

An LIF detector was integrated into a CE system based on silver mirror coating detection window and small-angle optical deflection from collinear configuration. For this detection scheme, the incident light beam was focused on capillary through the edge of a lens, resulting in a small deflection angle that deviated 18 degrees from the collinear configuration. Meanwhile, the excitation light and emitted fluorescence were effectively reflected by silver mirror coating at the detection window. The fluorescence was collected through the center of the same lens and delivered to a PMT in the vertical direction. In contrast to conventional collinear LIF detection systems, the fluorescence intensity was greatly enhanced and the background level was significantly eliminated. FITC and FITC-labeled amino acids were used as model analytes to evaluate the performance with respect to design factors of this system. The limit LOD was estimated to be 0.5 pM for FITC (S/N = 3), which is comparable to that of optimized confocal LIF systems. All the results indicate that the proposed detection scheme will be promising for development of sensitive and low-cost CE system.