Patent ID: 7961326

Claim:
A method for detecting concentration of an analyte in a fluid, the method comprising: providing a reflective optical cavity system having two or more light-transmissive regions at least partially bounded by components having light-transmissive and light-reflective properties, at least two of the components having substantially parallel surfaces; detecting an optical property of a first region of the two or more regions in the system, the first region located in a container having a reservoir for one or more modifiers of one or more optical properties of the first region, the movement of said one or more modifiers being responsive to changes in concentration of said analyte; detecting an optical property of a second region of the two or more regions in the system, the second region located in a container having a reservoir for one or more modifiers of one or more optical properties of the second region; the movement of said one or more modifiers being responsive to changes in concentration of a compound other than said analyte in the fluid; using said detected optical property of the first region and said detected optical property of the second region to separate the effect of said analyte on said detected optical property of the first region from the effect of said compound other than said analyte, said compound being an interfering compound; and determining the concentration of the analyte based on the difference in the effect of the analyte and the effect of the compound other than the analyte.