Use of Time Resolution To Eliminate Bilirubin Interference in the Determination of Fluorescein

Time-resolved fluorescence spectrometry is used to eliminate bilirubin interference in the fluorometric determination of fluorescein. Despite complete spectral overlap of the excitation and emission of these two species, a difference in fluorescence lifetime provides the selectivity parameter used In this method. Results for the determination of 0.300 nM fluorescein In the presence of up to 35.00 μM bilirubin (1:8.3 X 10⁴) using a sampling oscilloscope and an optical delay line show excellent accuracy (<5%) and precision (relative standard deviations < 4%) In all cases. Measurements are simple and rapid and require approximately 30 s/sample.