Abstract: A high sensitivity fluorescence and absorption detector comprising an elongated substantially cylindrical flow cell connected to and receiving the outflow of a fluid chromatography column; a mechanism for projecting a fluorescence generating beam of electromagnetic energy along on an axis substantially coincident with the axis of the flow cell; the flow cell including an elongated substantially cylindrical midsection housed by a tubular capillary transparent to the fluorescent radiation generated by the beam; a fluorescence integrating sphere completely surrounding the midsection of the capillary, the integrating sphere collecting at least about 3 pi steradian of the fluorescent radiation emanating through the capillary tube and into the sphere; the beam being projected to enter one end of the cylindrical flow cell, focus at about the center point of the axis of the cylindrical midsection, emanate through the other end of the flow cell and impinge upon a photodetector for detecting the portion of the beam whi