Comparison of orthogonal and collinear geometric approaches for design of a laboratory constructed diode laser induced fluorescence detector for capillary electrophoresis

This work describes the design and construction of two sensitive fluorescen ce detectors for capillary electrophoresis employing a semiconductor diode laser as the light source. The two systems employed different geometric app roaches - an orthogonal design and a collinear design, for collection of th e fluorescence. The systems were evaluated using Cy5.29 carboxylic acid, a far-red dicarbocyanine dye. A limit of detection (LOD), calculated as three times the standard deviation of the blank signal, of 7.4 x 10(-11)M was ob tained using the orthogonal system. The precision and accuracy of the assay determined using the orthogonal sys tem were within 10% RSD and 10 % DFN (deviation from nominal) respectively. The collinear design yielded a LOD of 1.2 x 10(-12) M.