In this type of system the reactants are continuously injected and mixed directly in front of the detector. Steady-state photon emission can be obtained by adjusting the rate at which new reagents are introduced to match the rate at which they are being consumed. This type of measurement, however, consumes a much larger quantity of reagents, and therefore may be prohibitive in some applications. A number of instrument manufacturers provide sophisticated chemiluminescence systems with a wide range of sensitivities. These interferences can and do cause high background counts, and they can be particularly troublesome in luminol-based assays.
Additional factors affect the sensitivity of fluorescence measurements.
Most of them are contained in the efficiency factor list presented above. If the concentration of fluorescent molecules is too high, reduction of the fluorescence intensity is observed. In addition, the need for a dilute solution limits the total number of emitted photons, thereby affecting sensitivity. However, in spite of these limitations, fluorescence has proven to be a very sensitive measurement tool. The combination of source fluctuations and scattered excitation that is not totally rejected by the emission wavelength selection device is another significant source of noise that can limit fluorescence detection.