TOTAL LIFETIME DISTRIBUTION ANALYSIS FOR FLUORESCENCE FINGERPRINTING AND CHARACTERIZATION

A new technique, total lifetime distribution analysis (TLDA), is descr ibed for rapid, sensitive, and accurate lifetime characterization of c omplex samples. Multiharmonic Fourier transform technology in a commer cial, frequency-domain fluorescence lifetime instrument allows rapid a cquisition of TLDA data. High sensitivity derives from the use of the entire fluorescence emission from the sample in the lifetime measureme nt. The maximum entropy method (MEM) provides a consistent basis for m odeling of the lifetime data for accurate recovery of the total lifeti me distribution of the sample. Because MEM is self-modeling, it is not subject to the same sources of bias that influence nonlinear least-sq uares fits of lifetime data to a priori models. These features make TL DA an effective tool for sample characterization and fingerprinting th at is based on the responsiveness of fluorescence lifetime to the chem ical composition and dynamic processes that contribute to the uniquene ss of the sample. TLDA results are presented for coal liquids and a hu mic substance. The effect of signal intensity on lifetime recovery is investigated, and comparison is made between MEM and conventional nonl inear least-squares for data analysis.