Abstract
Cyclic voltammograms of nitazoxanide recorded at the hanging mercury drop electrode in the Britton-Robinson universal buffer of pH values 2 to 11 containing 20% (v/v) ethanol exhibited a single 4-electron irreversible cathodic peak corresponding to the reduction of its NO2 group to the hydroxylamine stage. Nitazoxanide was found to adsorb onto surface of the mercury electrode in a monolayer surface coverage of 3.16×10-10 mol cm-2 in which each adsorbed molecule occupies an area of 0.525 nm². Based on its adsorption behavior onto the mercury electrode surface, validated linear sweep (LS), differential pulse (DP) and square wave (SW) adsorptive cathodic stripping voltammetric methods were described for determination of bulk nitazoxanide. Limits of detection of 1.5×10-10, 2.4×10-10 and 3.0×10-11 mol L-1 and limits of quantification of 5.0×10-10, 8.0×10-10 and 1.0×10-10 mol L-1 nitazoxanide in the bulk form were achieved by means of the described LS, DP and SW adsorptive cathodic stripping voltammetric methods, respectively. The described methods were successfully applied for determination of nitazoxanide in its pharmaceutical formulation (Cryptonaz powder) and in spiked human serum without the necessity for sample pretreatment, time consuming extraction steps or formation of colored chromogens prior to the analysis. Besides, nitazoxanide was successfully determined without interference from its acid or base-induced degradation products indicating the stability-indicating power of the described voltammetric methods.
Highlights
Nitazoxanide [2-(5-nitro-1,3-thiazol-2-ylcarbamoyl) phenyl acetate] (Scheme A) has a broad-spectrumStripping Voltammetric Methods for Determination of the Antiparasitic Drug NitazoxanideJ
10.0 mL of the B-R universal buffer of pH 4 containing the appropriate concentration of the analyte were transferred into the micro-electrolysis cell and deoxygenated with pure nitrogen gas before measurements while a stream of nitrogen gas was kept over surface of the solution in the electrolysis cell during the measurements
Cyclic voltammograms of 1×10-4 mol L-1 nitazoxanide recorded at the hanging mercury drop electrode (HMDE) in the B-R universal buffer of various pH values (2 to 11) containing 20% (v/v) ethanol displayed a well-defined single 4-electron irreversible cathodic peak, Figure 1, which was attributed to reduction of its NO2 group to the hydroxylamine stage[15,16,17] as confirmed from controlled-potential coulometry measurements
Summary
Nitazoxanide [2-(5-nitro-1,3-thiazol-2-ylcarbamoyl) phenyl acetate] (Scheme A) has a broad-spectrum. The present work aimed to describe validated simple, fast and precise stability indicating adsorptive cathodic stripping voltammetric methods for trace determination of nitazoxanide in the bulk form, pharmaceutical formulation and in human serum without sample pretreatment, extraction or formation of colored chromogens prior to the analysis. 10.0 mL of the B-R universal buffer of pH 4 containing the appropriate concentration of the analyte (bulk nitazoxanide, Cryptonaz powder or spiked human serum) were transferred into the micro-electrolysis cell and deoxygenated with pure nitrogen gas before measurements while a stream of nitrogen gas was kept over surface of the solution in the electrolysis cell during the measurements. Quantification of nitazoxanide was performed by means of both calibration curve and standard addition methods
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