Supramolecular Solvent-Liquid-Liquid Microextraction Followed By Smartphone Digital Image Colorimetry For The Determination Of Curcumin In Food Samples

Smartphone digital image colorimetry (SDIC) was coupled with supramolecular solvent-based liquid-liquid microextraction (SMS-LLME) for the determination of curcumin. Images, captured for sample solutions placed inside a homemade colorimetric box, were split into their red-green-blue channels and the intensity of the blue channel was correlated to the concentration of curcumin. Optimum SDIC performance was achieved at a distance of 9.0 cm between the sample cuvette and the detection camera, a region of interest of 1600 px2 and a light source at 15% brightness. Optimum SMS-LLME efficiency was obtained with 1000 mu L of tetrahydrofuran/1undecanol (4:1, v/v) as the supramolecular extraction solvent, pH of sample solution adjusted to 7.0, and 2.0% (w/v) sodium chloride within 60 s extraction time. Limits of detection (LOD) were found in the range of 0.2-0.9 mu g mL-1 (0.04-0.18%, w/w). Calibration graphs demonstrated good linearity with coefficients of determination higher than 0.9965 and relative standard deviations lower than 8.5%. The proposed SMS-LLMESDIC method was applied to determine curcumin in turmeric and tea samples from which percentage relative recoveries between 94.0 and 104.0% were obtained.