A smartphone-based method for extraction-free antioxidant capacity analysis of emulsions on paper by the DPPH assay

We are proposing an alternative quantitative analysis method for emulsions. The method relies on a simple and rapid protocol for antioxidant capacity measurement on chromatography paper by a digital smartphone camera and colorimetric analysis. It requires no extraction or pre-treatment step, as the emulsion is applied directly on the DPPH reagent spotted on a paper strip. Reliable calibration curves (R²>0.980) are built in an antioxidant-free base cream. Commercial samples are analyzed after significant dilution in the base cream, as antioxidant levels in cosmetics or many food emulsions are greatly above the linear dynamic range of the proposed format. The significant dilution zeroes out any matrix effect. Relative error ≤ ± 12.61 % was achieved upon analysis of commercial samples. This method can be a greener and simpler tool, even in minimally equipped sites, for quality control of emulsions. Method outline:•Reflected light intensity measurements, by smartphone camera, can be an effective means for analysis of antioxidant capacity of emulsions.•A simplified, extraction-free format on chromatography paper has been validated.•The wide applicability of the paper-based format to the monitoring of antioxidant capacity of emulsions by smartphone, has been demonstrated for several antioxidants and different types of emulsion formulations.