Threshold detection using indicator-displacement assays: an application in the analysis of malate in Pinot Noir grapes

The mathematics for modeling indicator-displacement assay isotherms is presented and contrasted to the classical host-guest binding isotherm. It is shown that the signal response can be tuned to occur closer to 1 equiv of guest relative to a standard binding algorithm. This delay in response leads to a better triggering protocol for threshold detection schemes. The determination of malate in Pinot Noir must was calculated using this new mathematical model, which demonstrates how a color change can be tuned to occur near a desired concentration of analyte.