Estimation of Gallic Acid Using Vanadium(V)–Eriochrome Cyanine-R System and Application to Some Herbal Plants, Fruit Juices and Wine Samples

A simple, rapid and sensitive method for the estimation of gallic acid has been developed. It is based on reduction of V(V) by gallic acid to V(IV) which forms complex with Eriochrome cyanine-R (ECR) in presence of cetyl trimethyl ammonium bromide (CTAB) resulting in a stable violet colored species. This showed maximum absorption at 580 nm. The calibration line was linear for gallic acid concentration range of 0.4-9.0 μg/mL, having limit of detection (LOD) and limit of quantification (LOQ) as 0.0044 and 0.0146 μg/mL respectively. Molar extinction coefficient and Sandell’s sensitivity were found to 8.12x10 L mol cm and 0.56x10 μg/cm, respectively. Interference study was also carried out for various species. The accuracy of the proposed method was assessed by Student’s t test and variance ratio F test and the results were comparable with reference 4-nitrobenzenediazonium tetrafluoroborate (NBD) method. The method was successfully used in determining gallic acid in wine, fruit juice and herbal plant samples.