3th WCSET-2014 at Nepal
Applied Sciences Session:
Title:
Evaluation of antioxidant capacities in teas by lab
built flow-injection analysis system
Authors:
Kisan Koirala, Jose Hernandez Santos
Abstract:
A low-cost amperometric flow injection analysis system
(FIAS) utilizing glassy carbon electrode was constructed
and tested for its use in the continuous monitoring of
antioxidant capacities of teas and coffees samples.
Standard solutions of ascorbic acid in 0.1 M KNO3 were
analyzed to establish the figures of merit of the FIAS
in amperometric mode. Optimum potential was determined
from the generated hydrodynamic voltammograms while the
linear dynamic range, sensitivity and detection limit
were calculated based on the data obtained using their
respective optimum applied potentials. The results of
this analysis were expressed in terms of ascorbic acid
equivalent (AAE) unit. The amperometric detection
resulted in well-defined linear concentration dependence
peak anodic current in a range between 0.5 mM to 40 mM
of ascorbic acid Calibration curve of amperometric FIAS
showed slope of 2.8622 μA/mmol and R2 of 0.9916. Limit
of detection was calculated as 0.0549 mM which were
calculated from standard deviation of 0.5 mM signal
(n=8). As an application, the flow injection analysis
system was used to estimate the antioxidant activities
of some common teas and coffees which are widely
consumed in Brunei Darussalam. The short analysis time
involved in flowinjection techniques (90 samples h-1)
resulted in a high throughput analytical method for
estimating the total antioxidant activities. Moreover,
this analysis method proved to be simpler, cheaper and
more practical alternative method of evaluating
antioxidants that undergo chemical decomposition when
exposed to atmospheric oxygen over a certain period of
time.
Keywords: Flow Injection
Analysis, Amperometric Detection, Antioxidant, Ascorbic
Acid, Tea and Coffee
Pages:
589-593