A Sensitive Colorimetric Detection of Ascorbic Acid in Pharmaceutical Products Based on Formation of Anisotropic Silver Nanoparticles

A sensitive colorimetric method for the detection of ascorbic acid was proposed in this research based on the reduction of silver ions by ascorbic acid in the presence of citrate-stabilized silver seeds, additional trisodium citrate and a polymer such as polyvinylpyrrolidone. The color of the stable sol is controlled by varying the concentration of trisodium citrate (TSC), polyvinylpyrrolidone, silver nitrate and silver seeds. The reduction of Ag+ to triangle silver nanoparticles (Ag-NPs) by ascorbic acid in the presence of trisodium citrate (TSC) and silver seeds produced two very intense surface plasmon resonance peaks of Ag-NPs. The plasmon absorbance of Ag-NPs allows the quantitative spectrophotometric detection of the ascorbic acid. The calibration curve derived from the changes in absorbance at  = 427 nm was linear, with the concentration of ascorbic acid in the range of 6:010􀀀6 to 8:010􀀀5 M. The method was applied to the determination of ascorbic acid in pharmaceutical formulations with satisfactory results.