SmartFluo: A Method and Affordable Adapter to Measure Chlorophyll a Fluorescence with Smartphones

In order to increase the monitoring capabilities of inland and coastal waters, there is a needfor new, affordable, sensitive and mobile instruments that could be operated semi-automatically inthe field. This paper presents a prototype device to measure chlorophyll a fluorescence: the SmartFluo.The device is a combination of a smartphone offering an intuitive operation interface and an adapterimplying a cuvette holder, as well as a suitable illumination source. SmartFluo is based on stimulatedfluorescence of water constituents such as chlorophyll a. The red band of the digital smartphonecamera is sensitive enough to detect quantitatively the characteristic red fluorescence emission.The adapter contains a light source, a strong light emitting diode and additional filters to enhancethe signal-to-noise ratio and to suppress the impact of scattering. A novel algorithm utilizingthe red band of the camera is provided. Laboratory experiments of the SmartFluo show a linearcorrelation (R2 = 0.98) to the chlorophyll a concentrations measured by reference instruments, suchas a high-performance benchtop laboratory fluorometer (LS 55, PerkinElmer).