Tables at a glance

Table 1

Table 2

Figures at a glance

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Table 1

Electrochemical sensors	Electrochemical methods	Linear ranges (μmol L-1)	Limit of detection (nmol L-1)	Reference
CuCo2O4/N-CNTs/MIP/GCE	DPV	0.005-0.1, 0.1-100	0.48	[8] Wang et al, 2019
NiMnO@pr-GO/GCE	DPV	0.1-234	0.09	[11] Vivekanandan et al. 2020
NSP-PC/GCE	LSV	0.1-45, 50-350	13	[12] Yalikun et al., 2019
CS-PC BPE/GCE	DPV	0.01-465	9	[13] Ranganathan et al. 2019
PrV/SCN/GCE	Amperometry	0.001-2444	0.8	[14] Kokulnathan and Chen 2019
ZIF-67C@rGO/GCE	DPV	0.5-1000	50	[15] Chen et al. 2019
O-gCN/GCE	DPV	0.01-2060	5	[36] Kesavan et al. 2021
C60-rGO-NF/SPE	SWV	0.5-34.0	35	[37] Materón et al. 2021
poly(L-Cys)/rGO-AgNPs/GCE	DPV	0.012-460	2.3	This work

Table 1: Comparison of the present method and other reported electrochemical methods for determination of metronidazole in recent three years

Table 2

Spiked (μg L-1)	Found (μg L-1)	Recovery (%)	RSD (%)
50	44.2	88.4	4.8
100	94.5	94.5	5.1
1000	106.8	106.8	3.4

Table 2: Recovery of the determination of MNZ in milk samples (n=5)

Scheme 1

Scheme 1: Synthesis of poly(L-cys)/rGO-AgNPs/GCE and the electrochemical determination of metronidazole

FIGURE 1

Figure 1: (A) Scanning electron microscope image of rGO-AgNPs at 2μm; (B) Transmission electron microscope images of rGO-AgNPs at 100nm, inset: Size distribution of AgNPs nanoparticles on rGO; (C) High-resolution transmission electron microscope images of AgNPs nanoparticles on rGO at 5nm, inset: Fast-Fourier transformation of high-resolution transmission electron microscope images; (D) UV-vis absorption spectrum of rGO-AgNPs and rGO-AgNPs + L-cys

FIGURE 2

Figure 2: (A) Cyclic voltammetry of GCE, rGO-AgNPs/GCE, poly(L-cys)/GCE and poly(L-cys)/rGO-AgNPs/GCE in 0.02 mg mL-1 metronidazole solution, containing 0.1 mol L−1 KCl. (B) Successive cyclic voltammetry behavior of metronidazole with a concentration of 0.02 mg mL-1 metronidazole solution containing 0.1 mol L−1 KCl. Scan rate: 0.1 V s-1

FIGURE 3

Figure 3: (A) Cyclic voltammetry of metronidazole (0.02 mg mL-1) in KCl, H2SO4, HAc, HCl, NaOH, and PBS (pH 7) (all supporting electrolytes were at 0.1 mol L-1) at the poly(L-cys)/rGO-AgNPs/GCE. (B) Cyclic voltammetry of metronidazole in PBS solutions with different pHs. Inset: a linear regression plot of Epc vs. pH. (C) Influence of accumulation times on poly(L-cys)/rGO-AgNPs/GCE in metronidazole solution (0.02 mg mL-1). Inset: cathodic currents for Epc1 (the black curve) and Epc2 (the red curve)

FIGURE 4

Figure 4: (A) Cyclic voltammetry of GCE, rGO-AgNPs/GCE, poly(L-Cys)/GCE, and poly(L-cys)/rGO-AgNPs/GCE in 1.0 mmol L-1 K3[Fe(CN)6]. (B) Electrochemical impedance spectroscopy of GCE, rGO-AgNPs/GCE, poly(L-cys)/GCE and poly(L-cys)/ rGO-AgNPs/GCE in 5.0 mmol L−1 K3[Fe(CN)6]/K4[Fe(CN)6] containing 0.1 mol L−1 KCl. (C) Chronocoulometry of GCE and poly(L-cys)/rGO-AgNPs/GCE in 1.0 mmol L−1 K3[Fe(CN)6], containing 1 mol L−1 KCl. (D) Cyclic voltammetry of metronidazole (0.02 mg mL-1) on poly(L-cys)/rGO-AgNPs/GCE at different scan rates: i.e. 50–300 mV s-1. Inset: linear regression plot of Epc1 (or Epc2) vs. lnv

FIGURE 5

Figure 5: DPV characterization of metronidazole at different concentrations: i.e., 0, 2×10-6, 8×10-6, 8×10-5, 2×10-4, 4×10-4, 8×10-4, 2×10-3, 4×10-3, 8×10-3, 2×10-2, 4×10-2, and 8×10-2 mg mL-1. Inset: calibration curve and peak currents of poly(L-cys)/rGO-AgNPs/GCE in KCl (0.1 mol L-1) and the magnifying superposed DPV i-Epc curves for low concentrations (0, 2×10-6, 8×10-6, 8×10-5, 2×10-4, 4×10-4, 8×10-4 mg mL-1). upper inset: the linear regression equation between concentration of metronidazole and Ipc. Bottom inset: the larger version of curves in lower concentrations