A method and associated apparatus for measuring chemical concentration in a liquid sample based on spatial separation and resolution of light is disclosed. The method is preferably applied to sensitive, quantitative, luminescence-based biosensors which reads the analyte concentration via spatial distribution of the emitted light. The detection of light is used to assess the spatial position, rather than the intensity or wavelength, of emitted light. A bioluminescent or chemiluminescent reaction requiring, for example, ATP, NADPH or NADH as a specific, and sensitive co-factor is used. ATP or NADH concentration is modulated, “tuned,” and/or regulated via, for example, an enzyme which consumes (“consumase”) ATP, NADPH, or NADH, thereby producing a spatial distribution of ATP or NADH and a spatial distribution in the emitted light. By appropriate control of the consumase or “synthase” activity and kinetics, a sensitive, specific, and easily readable luminescent pattern is produced, permitting detection.