A handheld smartphone-controlled spectrophotometer based on hue to wavelength conversion for molecular absorption and emission measurements

Abstract An improved design for a handheld smartphone-based spectrometer that works in both absorption and emission modes is proposed. The device, named Spectrophone, comprises modules made in MDF, an embedded light source designed for absorption mode, a DVD for the diffraction grating, and a smartphone to process the image data acquired. A user-friendly homemade software decompose the pixels from shots of spectral images into their RGB and hue (H) values which are processed by a simple algorithm developed to convert H values to their corresponding wavelengths. Analytical signals for the absorption mode are provided by an empirical equation based on RGB vector norms (||vRGB||) taken in blank and after light absorption, while ||vRGB|| is directly used to acquire emission signals. The Spectrophone was applied to determine Fe2+ in medicine samples and Na+ in saline solution and natural water samples. No statistically significant differences were observed in comparison with commercial instruments (α = 5%). The figures of merit of the Spectrophone were very good, with limits of quantification of 70 μg L-1 for absorption and 60 μg L-1 emission modes, respectively, and high linearity (R2 > 0.9995). High accuracy, simplicity, a user-friendly application and low-cost make this handheld device an attractive alternative for the absorption/emission measurements.

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