Anodic polarographic determination of lansoprazole and omeprazole in pure form and in pharmaceutical dosage forms

Lansoprazole (LNS) and omeprazole (OMP) are therapeutically important drugs, and the need arose for a simple, reliable method for their content uniformity of their tablets. The anodic polarographic behavior of lansoprazole and omeprazole has been studied in Britton-Robinson buffer (BRb) over the pH range 4.1-11.5. In BRb of pH 7 well-defined anodic waves were produced with diffusion-current constant (Id) of 1.70 +/- 0.01 (n = 6) and 1.66 +/- 0.01 (n = 8) for LNS and OMP, respectively. The current-concentration plots were rectilinear over the ranges of 4-24, 2-16 mug mL(-1) using Direct Current (DCt) mode for LNS and OMP, respectively and over the range 2-18, 0.4-12 mug mL(-1) using the Differential Pulse Polarographic (DPP) mode for LNS and OMP, respectively. The detection limits (S/N = 2) using DPP mode were 0.2 mug mL(-1) (5.41 x 10(-7) M) and of 0.05 mug mL(-1) (1.45 x 10(-7) M) for LNS and OMP, respectively. The proposed method was successfully applied to the analysis of the two drugs in their commercial capsules. The average percent recoveries were favorably compared to those obtained by reference methods, with satisfactory standard deviations. A pathway for the electrode reaction in both cases was postulated. The proposed method is characterized by being simple, accurate and stability-indicating.