Determine the selectivity of membrane - based electrochemical biosensor to detect ascorbic acid
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Date
2019-06
Authors
Nur Najwa Syazwani Binti Awang
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Abstract
The aim of this research is to determine the selectivity of nylon 6 membrane-based
electrochemical biosensor to detect ascorbic acid (AA). The nylon 6 membrane is
synthesized from nylon 6 beads (polymer) at 18wt%, 76wt% of formic acid (solvent)
as well as 6wt% of methanol as the non-solvent. In this work, the effect of AA
concentration (80Mm, 60mM, 40mM, 20mM and 10mM) and selectivity for
different volume percentage of citric acid (CA) to AA (0/100, 15/85, 30/70, 70/30,
85/15 and 100/0) were evaluated through cyclic voltammetry (CV) and
electrochemical impedance spectroscopy (EIS). The nylon 6 membrane has also been
characterized using scanning electron microscopy (SEM), fourier-transform infrared
(FTIR) and porometer to determine the surface morphologies, functional group and
pore characteristics of the membrane, respectively. SEM result shown nylon-6
membrane with micron-pores distributed on the membrane surface. Meanwhile,
FTIR results indicated that the membrane possess with important functional group of
nylon-6 membrane and porometer revealed narrower pore size distribution. Based on
the electrochemical analysis of membrane through CV, it was found that the higher
the concentration of AA, the higher the current detected. Similarly, for selectivity
test, the higher the volume percentage of AA, the higher the current peak for AA.
Concentration of AA and selectivity of CA to AA were found linearly proportional to
the peak current, with R
2 of 0.9897 and 0.9379, respectively. Furthermore, EIS
results for all mixed samples of CA and AA had demonstrated in linear lines, which
indicate lower resistance for electron charge transfer with increased kinetic for the
ions transfer. Finally, by using the calibration curve, the concentration of AA and the percentage volume of AA in the real sample, orange fruit was found to be 1.94 mM and 2.33 v%, respectively.