Specific, accurate and precise NMR methods were developed for determining miconazole, metronidazole and sulfamethoxazole antibiotic drugs in authentic, pharmaceutical and urine samples. Proton nuclear magnetic resonance spectroscopy (1H NMR) with maleic acid as an internal standard and DMSO-d6 as NMR solvent were used. 1H NMR signals at 9.0, 8.06, 7.50 and 6.26 ppm corresponding to miconazole, metronidazole, sulfamethoxazole and maleic acid were respectively used for calculating the concentrations of drugs per unit dose. Average percent recoveries of (97.54–101.10), (98.06–100.46) and (97.83–102.83) with average uncertainties of 1.02, 0.45 and 0.86 were respectively obtained for determining authentic samples of miconazole, metronidazole and sulfamethoxazole in the concentration range of 0.92–170 mg/0.6 ml DMSO-d6. In pharmaceutical formulations and urine samples, average percent recoveries in the ranges of 97.50–101.33 and 94.46–100.86 were respectively obtained. Relative standard deviations (R.S.D.) ≤2.68 were obtained for analyzing the three drugs in authentic, pharmaceutical and urine samples.
Admixtures of the three drugs in authentic, pharmaceutical and urine samples were analyzed. Good precisions (0.79–2.99%) and recoveries (93.40–104.97%) were obtained indicating the high selectivity and resolving power of the developed NMR methods and no needs for separation steps.
Applying statistical Student t-test revealed insignificant difference between the real and measured contents at the 95% confidence level. F-test revealed insignificant difference in precisions between the developed NMR methods and HPLC methods reported for analyzing miconazole, metronidazole and sulfamethoxazole.