RESUMO
Simple, reliable, and sensitive kinetic spectrophotometric method has been developed for the simultaneous determination of diloxanide furoate and metronidazole using H-point standard addition method (HPSAM). The method is based on the oxidation rate difference of diloxanide and metronidazole by potassium permanganate in basic medium. A green color has been developed and measured at 610 nm. Different experimental parameters were carefully optimized. The limiting logarithmic and the initial-rate methods were adopted for the construction of the calibration curve of each individual reaction with potassium permanganate. Under the optimum conditions, Beer's law was obeyed in the range of 1.0-20.0 and 5.0-25.0 µg ml(-1) for diloxanide furoate and metronidazole, respectively. The detection limits were 0.22 µg ml(-1) for diloxanide furoate and 0.83 µg ml(-1) for metronidazole. Correlation coefficients of the regression equations were greater than 0.9970 in all cases. The precision of the method was satisfactory; the maximum value of relative standard deviation did not exceed 1.06% (n=5). The accuracy, expressed as recovery was between 99.4% and 101.4% with relative error of 0.12 and 0.14 for diloxanide furoate and metronidazole, respectively. The proposed method was successfully applied for the simultaneous determination of both drugs in pharmaceutical dosage forms and human urine samples and compared with alternative HPLC method.
