New directions in near-IR fluorescence detection for capillary electrophoresis

Because of the small sample sizes that are typically inserted onto the separation column in capillary electrophoresis (1-100 nL), ultrasensitive detection strategies are required. The common detection approach used in CE is laser-induced fluorescence with He-Cd, Ar or Kr ion laser excitation. We are developing a detector system which utilizes solid-state diode lasers and avalanche photodiodes to produce a low-cost, durable and ultrasensitive fluorescence detector for CE applications. Along these lines, we have prepared some labeling dyes which readily conjugate to primary bioamines and show absorption and emission properties in the near-IR allowing low-level analyses of these target analytes in complex sample matrices. Our discussion will focus on the properties of diode lasers and avalanche diodes for fluorescence detection in CE applications. In addition, we discuss the characteristics of these near-IR dyes and tagging dyes synthesized in our laboratory for the covalent labeling of bioamines and their use in CE. The specific bioanalysis examples that we present utilizing near-IR fluorescence detection for CE are amino acids separations. In addition, we also discuss the ability to do time-resolved fluorescence measurements during CE for peak identification purposes.