Internal Reference For Chemically Modified Spheres

Abstract

A probe system for monitoring chemical activity of a target chemical in an environment has first and second marker compounds each bonded to a common substrate to keep the respective markers in physical proximity. The first marker is a chemical that has a maximum emission intensity at a first wavelength, and it is chemically shielded from the environment being studied. The second marker is a chemical that, when in a first state, has a maximum emission intensity at a second wavelength different from the first wavelength and which, in a second state, does not have a maximum emission intensity at the second wavelength. The second marker is convertible between said states through chemical reaction with the target chemical. The common substrate is a carrier particle, the first marker being impregnated within the carrier particle and the second marker being chemically bonded to the exterior surface of the carrier particle. The carrier particle may be a polymeric material, such as polystyrene, especially formed into a microsphere. The second marker may be in the second state prior to chemical reaction with the target chemical and is converted to the first state after chemical reaction with the target chemical, or it may be in the first state prior to chemical reaction with the target chemical, convertible to the second state by the chemical reaction with the target chemical.