Applications of Laser Fluorimetry to Microcolumn Liquid Chromatography

Laser-induced fluorescence (LIF) is examined as a sensitive and selective detector for microcolumn liquid chromatography (LC). This detector employs a cw helium-cadmium laser (325 nm, 5-10 mW) as the excitation source together with a simple filter/ photomultiplier optical system. Several flowcells are evaluated: (1) a flowing droplet; (2) an ensheathed effluent stream; and (3) a fused-silica capillary. The latter is judged to be the most promising for general use. The LIF detector is capable of sensing femtogram amounts of model solutes (coumarin dyes), and the response is linear over more than eight orders of magnitude in concentration. The potential of combining the high separation power of microcolumn LC with the high sensitivity of LIF detection is demonstrated through the analysis of multicomponent mixtures of polynuclear aromatic hydrocarbons and derivatized amino acids.