Background: The total antioxidant capacity of yam food grown in southern African regions
was investigated by a polyglycine-glassy carbon modified electrode. The modified electrode was fabricated
using glycine solution on glassy carbon electrode by electrodeposition method. The proposed
modified electrode is found to be nearly 3-fold more sensitive than the bare electrode. For the measurement
of the total antioxidants of yam, differential pulse stripping voltammetry (DPSV) is employed
with standard quercetin compound.
Methods: The total antioxidant capacity of yam was deduced by DPSV and cyclic voltammetry (CV)
methods. The basic parameters for the stripping technique such as pH, accumulation time and accumulation
potential were optimized as 20 s, 200 mV and a pH of 3 Britton-Robinson (B-R) buffer solutions
in 0.5 mg quercetin/L, respectively.
Results: In the optimization condition, the linear working range was determined between 5.0 μg/L and
80.0 μg/L for the quercetin. The detection (LOD) and quantification (LOQ) limits of quercetin were
found to be 0.39 μg/L and 1.39 μg/L on the modified electrode by DPSV, respectively. The procedure
was also applied to natural yam samples and total antioxidant capacity of 0.1 kg of yam was determined
as 96.15 ± 0.85 μg/L of equivalent quercetin at 95% confidence level with the relative standard
deviations of 0.88%.
Conclusion: Sensitive and selective voltammetric method was developed for the determination of total
antioxidant capacity in yam. Moreover, the modified polyglycine-MWCNT electrode was constructed
more selectively for quercetin. As a result, a simple, sensitive and rapid new voltammetric
method for the determination of antioxidants has been developed using the modified electrode.