Scheme 1.
Chemical structure of MTZ.
Fig 1.
Cyclic voltammograms of GCE in pH 3.0 PBS containing 1.0 mM ARS scanned between -0.2 V to +1.8 V at 100 mV/s for 15 cycles.
Inset: cyclic voltammograms of (A) bare GCE and (B) stabilized PARS/GCE in a monomer free 0.5 M H2SO4 scanned between -0.8 and +0.8 V at 100 mVs-1.
Fig 2.
Cyclic voltammograms of (1) bare GCE and (2) PARS/GCE in pH 7.0 PBS containing 10.0 mM [Fe(CN)6]3-/4- and 0.1 M KCl. Scan rate 100 mV s-1.
Fig 3.
Nyquist plots for (a) bare GCE and (b) PARS/GCE in pH 7.0 PBS containing 10.0 mM [Fe(CN)6]3-/4- and 0.1 M KCl at frequency range: 0.01–100,000 Hz, applied potential: +0.23 V, and amplitude: 0.01 V.
Table 1.
Summary of the calculated values of selected RC-elements.
Fig 4.
Cyclic voltammograms of bare GCE (a & c) and PARS/GCE (b & d) in the absence (a & b) and presence (c & d) of 1.0 mM MTZ in pH 7.0 PBS at scan rate 100 mV s-1.
Inset: corrected for blank cyclic voltammograms of bare (a) and PARS/GCE (b).
Fig 5.
(A) Cyclic voltammograms of 1.0 mM MTZ at PARS/GCE in PBS of different pH values (a–g: 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, and 10.0, respectively) at scan rate of 100 mV s-1. (B) Plot of reductive (a) Ip and (b) Ep versus pH for 1.0 mM MTZ in PBS values at PARS/GCE. Scan rate: 100 mV s-1.
Scheme 2.
The proposed reaction mechanism of MTZ at PARS/GCE.
Fig 6.
Cyclic voltammograms of 1.0 mM MTZ in pH 7.0 PBS at PARS/GCE at various scan rates (a–k: 20, 40, 60, 80, 100, 125, 150, 175, 200, 250, and 300 mV s-1, resp.).
Fig 7.
Plot of Ip versus (a) v1/2 and (b) v for 1.0 mM MTZ in pH 7.0 PBS at PARS/GCE.
Fig 8.
Plot of log(Ip) versus log(v) in a scan rate range of 40–300 mV s-1.
Fig 9.
Corrected for blank SWVs of 1.0 mM MTZ in pH 7.0 PBS at (a) bare GCE, and (b) PARS/GCE at step potential: 4 mV, amplitude: 25 mV and frequency: 15 Hz.
Fig 10.
Representative background corrected SWAdCSV of PARS/GCE in pH 7.0 PBS containing tablet sample spiked with various concentrations of standard MTZ (a–e: 0.0, 25.0, 50.0, 75.0, 100.0, and 125.0 μM, respectively).
Inset: plot of mean±SD (n = 3) of Ip versus spike concentration of MTZ.
Fig 11.
SWAdCSV of EPHARM MTZ sample in PBS pH 7.0 spiked with 50 μM of standard MTZ.
Fig 12.
SWAdCSV of pH 7.0 PBS containing EPHARM MTZ tablet solution in the presence of various concentrations of UA and AA.
Table 2.
Summary results of level of MTZ in tablet sample, spike recovery, and interference recovery at 100 and 150% of selected potential interferents.
Table 3.
Comparison of several electrochemical methods for MTZ determination.