Quantification of Sub-Nanomolar Levels of Gallic Acid by Adsorptive Stripping Voltammetry

The voltammetric behavior of gallic acid (GA) on a hanging mercury drop electrode (HMDE) has been investigated by cathodic adsorptive stripping voltammetry (AdCSV). Gallic acid (3,4,5-trihydroxybenzoic acid) is a natural phenolic compound which can generate a well defined reduction peak at around -1.04 V (versus Ag/AgCl) in 0.1 M borax buffer solution (pH 7.53). The parameters affecting the response of gallic acid, such as pH, accumulation time, accumulation potential and scan rate are optimized for the determination of GA. Under the optimized conditions, the peak current change linearly with the GA concentration in the range of 0.1 to 600 ng/ml. The lowest detectable concentration of GA is 0.05 ng/ml after 100 s accumulation time. The method has been successfully applied to the determination of GA in tea, urine and plasma blood serum. The results show that the sensitivity of the method is highest among the existing methods.