Dual-Mode Plasmonic and Paper-Based Colorimetric Assays for the Determination of Riboflavin in Green Leafy Vegetables and Whole Grains
Tikeshwari, Kamlesh Shrivas, Sanyukta Patel, Monisha Monisha, Tushar Kant, Santosh Singh Thakur, Shamsh Pervez, Manas Kanti Deb, Kallol K. Ghosh
Abstract
We developed plasmonic and paper-based colorimetric assays using poly(vinyl alcohol)-capped silver nanoparticles (AgNPs) to detect vitamin B 2 in food samples. Plasmonic colorimetry shifts the plasmonic band from 405 to 445 nm in the presence of B 2, while the paper-based method changes the color of AgNPs from yellow to reddish yellow. B 2 levels were quantified with a smartphone-assisted RGB color detector app. Experimental and density functional theory investigations validated the selective riboflavin–AgNP interaction. The plasmonic assay detected B 2 in the range of 0.01–1.0 μg mL –1 with a detection limit of 0.008 μg mL –1, while the paper-based assay detected in the range of 0.2–2.0 μg mL –1 with a detection limit of 0.09 μg mL –1 . Both methods had low relative standard deviations of 3.5% (plasmonic) and 4.7% (paper-based). The cost-effective, user-friendly, paper-based assay is particularly suitable for resource-limited settings, validated against high-performance liquid chromatography and Student’s t -test for accuracy.