Amperometric carbon paste enzyme electrodes with Fe₃O₄ nanoparticles and 1,4-Benzoquinone for glucose determination

Figures & data

Figure 1. (A) Cyclic voltammograms of (a) UCPE, (b) Fe₃O₄-CPE, (c) BQ-CPE and (d) BQ-Fe₃O₄-CPE at 10 mVs^‐1, (B) curve of the anodic peak current versus the square root of the scan rate for Fe₃O₄-CPE (inset: cyclic voltammograms at scan rates of 10, 25, 50, 75, 100 and 150 mVs⁻¹) in 0.1 M KCl solution containing 1 mM Fe(CN)₆^3−/4−.

Figure 2. The Nyquist curves of (a) UCPE and (b) Fe₃O₄-CPE (c) BQ-CPE and (d) BQ-Fe₃O₄ CPE in 0.1 M KCl solution containing 1 mM Fe(CN)₆^3−/4−.

Figure 3. (A) Calibration curves for H₂O₂: (a) BQ‐Fe₃O₄‐CPE, (b) Fe₃O₄‐CPE (c) BQ‐CPE and (d)UCPE (0.05 M pH 7.5 phosphate buffer, + 0.30 V, nitrogen-saturated solution). (B) Calibration curves for glucose: (a) BQ‐Fe₃O₄‐CPEE, (b) Fe₃O₄‐CPEE (c) BQ‐CPEE and (d) UCPEE (0.05 M pH 7.5 phosphate buffer, + 0.30 V, oxygen-saturated solution).

Figure 4. The effect of buffer pH on the response of Fe₃O₄‐CPEE (0.05 M phosphate buffer, + 0.30 V).

Figure 5. (A) Effect of glucose concentration on the response of Fe₃O₄‐CPEE (B) Effect of glucose concentration on the response of BQ‐Fe₃O₄‐CPEE (inset: glucose response of the BQ‐Fe₃O₄‐CPEE at low concentrations) (0.05 M, pH 7.5 phosphate buffer, + 0.30 V, oxygen-saturated solution).

Table 1. Comparison of glucose concentration in serum samples using the modified enzyme electrode and the spectrophotometric method.

	Glucose (mg/dL)
	BQ-Fe3O4-CPEE^a	Spectrophotometric
Sample 1	70.05 ± 1.1	69
Sample 2	108.93 ± 2.6	109
Sample 3	123.15 ± 1.5	124
Sample 4	114.28 ± 1.7	115

^aEach value is the mean of three measurements.