Fluorometric determination of indocyanine green in plasma.

With this fluorometric method for measuring indocyanine green (ICG) in biological fluids, the limit of detection is an order of magnitude lower than for the traditional spectrophotometric procedure. The excitation and emission maxima are 780 and 810 nm, respectively. Agreement was excellent (r = 0.998) between direct results by this method and those by a liquid-chromatographic procedure with spectrophotometric detection. ICG breaks down in aqueous solution; the degradation products can be detected with liquid-chromatographic/spectrophotometric methods, but because the metabolites are not fluorescent, they do not interfere in the method present here. The increased specificity and sensitivity of this method should permit much more complete analysis of the kinetics of ICG disposition.