INDICATOR SUBSTANCE OF AN OPTICAL FLUORESCENCE MEASURING ARRANGEMENT FOR MEASURING THE pH OF A SAMPLE AND OPTICAL SENSOR WITH SUCH AN INDICATOR SUBSTANCE

摘要

An indicator substance for an optical luminescence measuring arrangement for the continuous reversible measurement of the pH of a sample within a measuring range (M) or interest, the luminescence decay time tau depends on the pH of the sample, has the properties below. The pKs of the acid or basic indicator substance in its electronic basic state (S0) lies in the measuring range of interest. The protonation rate kp of the base or the deprotonation rate kdp of the acid in the excited state (S1, X) of the indicator substance is smaller than the decay kA of the excited state and the luminescence decay times DOLLAR (t)S and tau B of the acid (AH*, BH<+>*) and basic (A<->*, B*) forms of the indicator substance differ. If the pKs* of the indicator substance in its electronically excited state (S1, X) lies in the measuring range of interest, the protonisation rate kp of the base or the deprotonisation rate kdp of the acid in the excited state (S1, X) of the indicator substance is greater than the decay rate kA of the excited state.