A newly developed method for determining molecular distribution functions is applied to a widely researched glucose affinity sensor. The reduction in fluorescence resonance energy transfer (FRET) to a malachite green (MG)-dextran complex from allophycocyanin (APC) bound to concanavalin A (ConA) due to displacement of the complex by glucose from ConA provides the basis of the assay. The higher sensitivity and specificity of a new approach to fluorescence decay analysis, over the methods based on conventional Forster-type models, is demonstrated and critical parameters in competitive binding FRET sensing derived.