Quantitative Fluorescence Photometry with Biological Fluids and Gases

Abstract

Longmuir and Knopp (1) have shown that the quenching of the fluorescence of pyrene butyric acid by oxygen (2) can be used to monitor oxygen concentration in tissue. However, since the fluorescence signal is also influenced by several other factors, such as

• 1) changes in the indicator concentration,

• 2) interaction of this indicator with other substances and

• 3) the filter effect of the tissue,

a quantitative evaluation meets with considerable difficulties. The error caused by concentration changes can be cancelled by using special indicators which change their spectra with the reaction. For example, Boldt and Lübbers (3) used ß-methyl umbelliferon as a pH indicator which has different excitation spectra for the dissociated and undissociated forms. The other errors cannot be taken into account without special measurements. The actual, possibly disturbed spectrum of the tissue can be related to the true indicator spectrum, if the indicator in the tissue is changed into its dissociated or undissociated form, e. g. on a deliberate change of the pH.