Inspection of Equation 2 reveals several ways to increase the fluorescence signal, including increasing the collection efficiencies, molar absorptivity, quantum yield, and intensity of excitation. Of these variables, the one that is most easily increased is the excitation intensity. Most commonly, this is achieved with laser-based excitation; however, one cannot simply increase the fluorescence signal without bound. For example, for weakly emitting samples, the water Raman scatter from aqueous samples can become so intense that it actually overwhelms fluorescence. Fortunately, techniques have been developed to alleviate these type of problems (5). In addition, at hight power densities even normally stable fluorophores begin to photodecompose. The only general recourse to this decomposition problem is to lower the incident power or employ a flowing sample stream.