Abstract

The rapid and accurate determination of physiological concentrations of biologically important gases, such as O₂ and CO₂, has recently become possible through the use of phase-modulation fluorometry¹ This technique measures the phase between modulated excitation and modulated emission. The lifetime of the fluorophore is changed by the presence of the gas, producing a phase shift that can be correlated with the concentration of the gas. Since the fluorescent decay acts as a filter for the modulated excitation source, significant phase shifts require modulation frequencies corresponding to the inverse of the fluorescence lifetimes.

© 1995 Optical Society of America