Abstract: A laser-induced fluorescence detector comprises a laser beam emitting device, a dichroic mirror to deviate the laser light orthogonally, a lens with a small numerical aperture, a ball lens, a unique cell within a capillary, the cell receiving a solute containing at least one unknown fluorescent substance at the laser wavelength, the same device collecting the fluorescence emitted by the fluorescent substance, with optical filters, a photomultiplier tube, and a computer for displaying results of the analysis. The ball lens converts the laser beam into a very small divergent beam, which allows a high irradiated volume in the capillary cell. The cell employs controlled geometric contours to prevent laminar mixing and turbulence during liquid flow, and the collecting device is a high numerical aperture device, for example, a ball lens.