Simultaneous absorbance, fluorescence and refractive index (SAFRIN) detection for Micro LC

Abstract Absorbance, fluorescence and refractive index detection are simultaneously accomplished in a Micro LC system. A unique double eccentric-bend fused silica capillary is employed with axial illumination to achieve a long path length, multisensing flow cell. Two different optical sources, one that excites fluorescence through absorption and one that is not absorbed by eluting analytes, are imaged into the bends with optical fibers, placed within the capillary lumen in separate legs of the device. Axially-propagating light exits at each bend where photodetectors simultaneously collect attenuated light, one signal based on absorption and the other signal based on refractive index. A nearby cylindrical lens, optical filter and photomultiplier tube collect fluorescence in the ‘absorption’ leg of the capillary. Thus, trifunctional detection is achieved in microscale liquid chromatography.