Simultaneous determination of organic analytes by reduced graphene oxide-azo dyes/gold nanoparticles modified glassy carbon electrode
The detection of biological molecules and monitoring of environmental contaminants is a demanding aspect in the field of analysis. Electrochemical sensors are one of the tools that attracted great attention in this field due to their applicability. In the present research work, glassy carbon elec...
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| Format: | Thesis |
| Language: | English |
| Published: |
2019
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| Online Access: | http://ethesis.upm.edu.my/id/eprint/14166/1/FS%202019%2065%20T.pdf |
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| Summary: | The detection of biological molecules and monitoring of environmental
contaminants is a demanding aspect in the field of analysis. Electrochemical
sensors are one of the tools that attracted great attention in this field due to their
applicability. In the present research work, glassy carbon electrode (GCE) was
modified by electrochemically reduced graphene oxide (ERGO) with two different
azo dyes i.e. poly(eriochrome black T) (pEBT) and poly(Procion Red 5-MX) poly
(PR) and gold nanoparticles (AuNPs) to obtain AuNPs/ERGO-pEBT/GCE and
AuNPs/ERGO-poly(PR)/GCE electrochemical sensors. The modified sensors
were characterised by field scanning electron microscopy (FESEM), Fourier
transform infrared spectroscopy (FTIR), electrochemical impedance
spectroscopy (EIS) and cyclic voltammetry (CV). The resultant modified sensors
revealed elevated electrocatalytic properties in comparison to other modified
GCEs. The prepared nanocomposites were used to simultaneously determine
ascorbic acid (AA), dopamine (DA), and uric acid (UA) as well as hydroquinone
(HQ), catechol (CC), and resorcinol (RC) in phosphate buffer solution (PBS).
Due to the synergistic effect, the modified electrodes had excellent
electrochemical catalytic activity towards the oxidation of two sets of analytes
which allowed their simultaneous determination.
The AuNPs/ERGO-pEBT/GCE showed good potential peak separations of 166
and 126 mV for DA-AA and UA-DA respectively when it was immersed in a
mixture solution of AA, DA, and UA. Simultaneous detection of HQ, CC, and RC
was performed with potentials separation of 111 and 383 mV for HQ-CC and
CC-RC, respectively, thus acknowledged the simultaneous detection of these
isomers.In the same manner, AuNPs/ERGO-poly(PR)/GCE was used to simultaneously
determine AA, DA, and UA where, the potential separations between DA-AA and
UA-DA were found to be 210 and 140 mV, respectively. The modified electrode
(AuNPs/ERGO-poly(PR)/GCE) has also been utilised in the simultaneous
detection of HQ, CC, and RC. DPV was carried out and the peak potential
separation between HQ-CC was 130 mV and CC-RC was 400 mV.
AuNPs/ERGO-pEBT/GCE revealed limit of detections (LODs) of 530, 9, and 46
nM, with sensitivities of 0.003, 0.164, and 0.034 μA/μM, when applied in
simultaneous detection of AA, DA, and UA. Whereas, the determination of HQ,
CC and RC acquired sensitivity of 0.04, 0.78, and 0.15 μA/μM and LODs of 15,
8, and 39 nM, respectively. The obtained LODs for AA, DA, and UA at
AuNPs/ERGO-poly(PR)/GCE were 54, 5.6, and 5.8 nM, respectively. Sensitivity
of this electrode in AA, DA, and UA mixture solution was 0.63 μA/μM for UA,
0.40 μA/μM for DA, and 0.48 μA/μM for AA. The three isomers; HQ, CC, and RC
showed sensitivies of 4.61, 4.38, and 0.56 μA/μM supplemented by LODs of 53,
53, and 79 nM at the same electrode in their ternary.
Both AuNPs/ERGO-pEBT/GCE and AuNPs/ERGO-poly(PR)/GCE showed
prominent selectivity toward the analytes (AA, DA, UA and HQ, CC, RC). In
addition, no interference effect with possible co-existence ions and compounds
that could hinder the analyte detection as well as presenting good repeatability,
reproducibility and favourable stability. The as-proposed electrochemical sensors
were applied successfully with outstanding recoveries in urine samples, vitamin
C tablets and synthetic wastewaters analysis.
The modified electrode AuNPs/ERGO-pEBT/GCE offered enhanced efficiency
in the simultaneous determination of dihydroybenzene isomers, while the
electrode AuNPs/ERGO-poly(PR)/GCE is demonstrated superior performance
towards determination of UA,DA, and AA. |
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