Laser-induced fluorescence detector having a capillary detection cell and method for identifying trace compounds implemented by the same device

A laser-induced fluorescence detector comprising:

• a laser source for emitting a laser beam,
• a unique cell substantially egg-shaped within a capillary, said cell receiving a solute containing at least one unknown fluorescent substance at the laser wavelength and employing controlled geometric contours to prevent laminar mixing and turbulence during liquid flow,
• means for illuminating by said laser beam said fluorescent substance flowing in the capillary, said illuminating means including a ball lens for converting a slightly converging laser beam coming from a small numerical aperture lens into a small divergent beam illuminating the volume of the cell,
• means for collecting the fluorescence emitted by the fluorescent substance, said collecting means including high numerical aperture means;
• said small numerical aperture lens, said capillary and said collecting means being disposed collinearly, and said ball lens being further used as the high numerical aperture means,
• means for filtering said collected fluorescence,
• photomultiplier tube means provided for processing said filtered and collected fluorescence, and
• means for analyzing signals generated by said photomultiplier tube means and for displaying results of said analysis,
• wherein said illuminating means and said cell are structured and arranged so as to maximize the volume irradiated by said laser beam.