Electrochemical Sensor for Simple and Sensitive Determination of Hydroquinone in Water Samples Using Modified Glassy Carbon Electrode

Abstract

This study addressed the use of manganese dioxide nanorods/graphene oxide nanocomposite (MnO₂ NRs/GO) for modifying a glassy carbon electrode (GCE). The modified electrode (MnO₂ NRs/GO/GCE) was used as an electrochemical sensor for the determination of hydroquinone (HQ) in water samples. Differential pulse voltammetry (DPV), cyclic voltammetry (CV), and chronoamperometry were used for more analysis of the HQ electrochemical behavior. Analyses revealed acceptable electrochemical functions with lower transfer resistance of electrons and greater conductivity of the MnO₂ NRs/GO/GCE. The small peak-to-peak separation is an indication of a rapid electron transfer reaction. Therefore, this result is probably related to the effect of the MnO₂ NRs/GO nanocomposite on the surface of GCE. In the concentration range of 0.5 μM to 300.0 μM with the detection limit as 0.012 μM, there was linear response between concentration of HQ and the current. The selectivity of the modified electrode was determined by detecting 50.0 μM of HQ in the presence of various interferent molecules. At the end, the results implied the acceptable outcome of the prepared electrode for determining HQ in the water samples.

Keywords: MnO2 NRs/GO nanocomposite; electrochemical sensing; hydroquinone; modified electrode; voltammetry.

Figure 1

FE-SEM image of GO (a) and MnO₂ NRs/GO nanocomposite (b).

Figure 2

Plot of the oxidation peak current of 200.0 μM HQ as a function of pH solution on MnO₂ NRs/GO/GCE in 0.1 M PBS at different pH value (2.0–9.0).

Figure 3

CVs of the (a) MnO₂ NRs/GO/GCE in 0.1 M PBS (pH = 7.0) in the absence of HQ), (b–e) bare GCE, MnO₂ NRs/GCE, GO/GCE and MnO₂ NRs/GO/GCE in 0.1 M PBS (pH = 7.0) with 200.0 μM HQ. The scan rate was equal to 50 mV s⁻¹.

Figure 4

CVs of 120.0 μM HQ on MnO₂ NRs/GO/GCE in 0.1 M PBS (pH = 7.0) at the various scanning rates (ν); (Curves a–n: (a) 5 mV/s, (b) 10 mV/s, (c) 20 mV/s, (d) 30 mV/s, (e) 40 mV/s, (f) 50 mV/s, (g) 60 mV/s, (h) 70 mV/s, (i) 80 mV/s, (j) 90 mV/s, (k) 100 mV/s, (l) 200 mV/s, (m) 300 mV/s, and (n) 400 mV/s. Inset: The plot of Ipa and Ipc vs. the square root of the scanning rate (υ^1/2).

Figure 5

Chronoamperograms for the different concentrations of HQ on the MnO₂ NRs/GO/GCE in 0.1 M PBS (pH = 7.0) in ranges between 0.1 and 2.0 mM (Curves a–d: (a) 0.1 mM, (b) 0.5 mM, (c) 1.5 mM, and (d) 2.0 mM). Insets: I-plots vs. t^−1/2 for chronoamperograms a–d (A) and the slope from the straight lines vs. the concentration of HQ (B).

Figure 6

DPVs for diverse concentrations of HQ on MnO₂ NRs/GO/GCE in 0.1 M PBS (pH = 7.0) in ranges from 0.5 to 300.0 μM (Curves a–n: (a) 0.5 μM, (b) 5.0 μM, (c) 10.0 μM, (d) 20.0 μM, (e) 30.0 μM, (f) 40.0 μM, (g) 50.0 μM, (h) 60.0 μM, (i) 70.0 μM, (j) 80.0 μM, (k) 90.0 μM, (l) 100.0 μM, (m) 200.0 μM, and (n) 300.0 μM). Inset: the related linear calibration curve of the peak current vs. concentration of HQ.