Breath analysis system

A device-implemented method of analyzing a disposable cartridge to measure a concentration of a breath analyte extracted by an interactant contained in the cartridge, the method comprising, by a device that comprises a plurality of light emitting diodes (LEDs), including a first set of one or more LEDs that emit light of a first wavelength and a second set of one or more LEDs that emit light of a second wavelength:

• during each of a plurality of measurement cycles performed over a cartridge analysis period:
• illuminating the disposable cartridge with the first set of LEDs, but not with the second set of LEDs, while generating a first measurement of an intensity of light reflected from the disposable cartridge, said first measurement corresponding to the first wavelength;
• and
• illuminating the disposable cartridge with the second set of LEDs, but not with the first set of LEDs, while generating a second measurement of an intensity of light reflected from the disposable cartridge, said second measurement corresponding to the second wavelength;
• and
• generating an analyte concentration measurement value based at least partly on the plurality of first and second measurements;
• wherein the measurement cycles are spaced apart in time and occur over a time period during which a reflectance of the interactant changes, such that the plurality of measurements indicate reflectance trends at each of the first and second wavelengths.