Voltammetric determination of montelukast sodium in dosage forms and human plasma

The voltammetric behaviour of montelukast (MKST) was studied using cyclic voltammetry, direct current (DC_t), differential pulse polarography (DPP) and alternating current (AC_t) polarography. MKST exhibited well-defined cathodic waves over the range pH range 1–5. No anodic waves were produced over the same pH range. At pH 1, the analytical pH; the diffusion current constant (Id) was 2.2 ± 0.01 μA l mmol^–1. The current concentration plot was rectilinear over the range 2–20 μg ml^–1 with correlation coefficient (n = 10) of 0.9943. The lower limit of detection (S/N = 2) was 0.2 μg ml^–1 (3.41 × 10^–7 M). The wave has been characterised as being diffusion-controlled, although adsorption phenomenon played a limited role in the electrode reaction. The proposed method was successfully applied to the determination of MKST in commercial tablets, and results were in agreement with those given with a reference HPLC method. The method was further extended to the in vitro determination of the drug in spiked human plasma. The mean % recovery (n = 5) was 101.38 ± 3.85. The number of electrons transferred in the reduction process could be accomplished and a proposal of the electrode reaction was proposed.