Three simple, accurate, sensitive and selective spectrophotometric methods (A, B and C) for the determination of famotidine (Fam) in bulk sample, in dosage forms and in the presence of its oxidative metabolites are described. The first method A is based on oxidation of the drug by N-bromosuccinimide (NBS) and determination of the unreacted NBS by measuring the decrease in absorbance of Amaranth dye (AM) at a suitable λmax (521 nm). The methods B and C involve addition of excess cerric sulphate and determination of the unreacted Ce(IV) by decrease the red colour of chromotrope 2R (C2R) at λmax 528 nm for method B or decrease the orange pink colour of rhodamine 6G (Rh6G) at λmax 526 nm for method C. Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges 0.1–2.4 µg mL for method A and 0.1–2.2 µg mL for methods B and C. The apparent molar absorptivity, Sandell sensitivity, detection and quantitation limits were calculated. For more accurate results, Ringbom optimum concentration ranges were 0.2–2.2 µg mL for method A and 0.2–2.0 µg mL for methods B and C. The stoichiometric ratio between the drug (Fam) and the oxidant (NBS or Ce) was estimated. The validity of the proposed methods were tested by analysing pure and dosage forms containing famotidine and in the presence of its oxidative degradates. Statistical treatment of the results reflects that the proposed procedures are precise, accurate and easily applicable for the determination of famotidine in pure form, in pharmaceutical preparations and in the presence of its oxidative degradates. |
