Quantitation of Vitamin C in Supplements Using Titrimetric, Molecular Absorption Spectroscopy and Digital Imagens

Abstract

In this research, it was presented a laboratory class where titrimetric and colorimetric methods were used to determine vitamin C levels in supplement pills. In the first part, vitamin C levels were measured in supplement pills using three titrimetric methods, back titration with sodium thiosulphate (Na2S2O3), direct titrations with potassium iodate (KIO3) and iodide (I2). Results obtained with trimetric methods were equivalent at 95 % confidence interval, methods were compared using one-way ANOVA). In the second part, a quick and low-cost colorimetric method was carried out. It was successfully used to measure vitamin C levels in supplement pills. It consists in reduction of the complex Fe 3+ and 1,10phenanthroline by vitamin C to form a reddish-orange colored complex that was measured at 510 nm. The colorimetric method was also carried out using digital images obtained with a flatbed scanner. RGB values were extracted from digital images using ImageJ's plugin ReadPlate in a simple and easy manner. The t paired test had shown that both methods were equivalent at 95 % confidence interval.