Patent ID: 6284544
Filing Date: 2001-09-04
Classification: G01N

Abstract:
A method of measuring metal ion concentration in an aqueous solution, the method comprising the steps(a) mixing said solution with a macromolecule having a photoluminescent label covalently attached; said macromolecule being able to reversibly bind a metal ion, resulting in the formation of a macromolecule-metal ion complex, wherein the ratio of the apparent photoluminescent lifetime of said photoluminescent label to the rotational correlation time of said macromolecule is in the range of 0.11 to 3.2;(b) irradiating said aqueous solution with polarized light at wavelengths strongly absorbed by said photoluminescent label;(c) resolving the photoluminescence emission from said irradiated aqueous solution into vector components parallel (I.parallel.) and perpendicular (I.perp.) to the plane of polarization of the exciting light;(d) calculating the photoluminescence anisotropy from the vector components of step (c) by applying the following equation: ##EQU3##wherein r is the anisotropy; I.parallel. is the intensity of the emission that is parallel to the plane of the polarized excitation; I.perp. is the intensity of the emission that is perpendicular to the plane of the polarized excitation; and(e) relating the photoluminescence anisotropy to a fraction of said macromolecule that is in the form of said macromolecule-metal ion complexes, and to an affinity constant of binding of said metal ion to said macromolecule, thereby determining said metal ion concentration.