Metronidazole concentration measured spectrophotometrically using a diazotization and coupling reaction with 5-sulphosalicylic acid

A novel, straightforward, and sensitive spectrophotometric technique for determining Metronidazole has been developed, this method relies on the reduction of metronidazole in acidic media using iron powder and then preparing diazonum ion by adding an equivalent amount of sodium nitrite to the reduced metronidazole in acidic medium and waiting for 3 min. before adding the reagent (5-sulphosalycilic acid) to produce a red color product that gives the highest absorption at the wavelength 503 nm, and the linearity of Beer's law was in the concentration range from 0.5 to 10 μg/ml, and the value of the determination coefficient for the standard curve was 0.9972, indicating statistically that it has excellent linear characteristics, the molar absorptivity was calculated and found to be 1.151 x104 L.mol-1.cm-1 and Sandell's sensitivity value is 0.01485 µg/cm2. The method has been successfully applied to the assay of Metronidazole in pure and pharmaceutical forms Tablet and oral suspension.