New method of rapid luminescence lifetime determination using square-wave excitation

A new rapid lifetime determination method (RLD) that uses a rectangular exc itation is presented. The information from the exciting, as well as the emi tting, portion is used to extract decay parameters for a single exponential decay. The lifetime is computed from the ratio of the integrals of the emi ssion during the excitation period and an equal time interval during the de cay (At). The new square-wave RLD method (SWRLD) shows speed similar to the standard RLD method but without the necessity of matching Deltat to the li fetime for precise results. Monte Carlo simulations are used to predict the capabilities of the SWRLD, and the theory is tested with a luminescent ter bium complex. The method is particularly applicable to rapid lifetime analy sis for high-performance liquid chromatography (HPLC) and for fluorescence microscopy. It lends itself to use with inexpensive square-wave modulated l ight-emitting diodes (LEDs).