Enhanced spectrophotometric determination of Losartan potassium based on its physicochemical interaction with cationic surfactant

• Calculation of the degree of drug/micelle interaction is reported.
• Understand the interactions with biomembranes and structure–activity relationship of drugs.
• Describing the effect of cationic micelles on the spectroscopic and acid–base properties of LST K.

In this study, a simple and sensitive spectrophotometric method was developed for determination of Losartan potassium (LST K), an angiotensin-II receptor (type AT1) antagonist, in presence of cationic surfactant cetyltrimethylammonium bromide (CTAB). The physicochemical interaction of LST K with CTAB was investigated. The effect of cationic micelles on the spectroscopic and acid–base properties of LST K was studied at pH 7.4. The binding constant (Kb) and the partition coefficient (Kx) of LST K-CTAB were 1.62 × 105 M−1 and 1.38 × 105; respectively. The binding of LST K to CTAB micelles implied a shift in drug acidity constant (ΔpKa = 0.422).The developed method is linear over the range 0.5–28 μg mL−1. The accuracy was evaluated and was found to be 99.79 ± 0.509% and the relative standard deviation for intraday and interday precision was 0.821 and 0.963; respectively. The method was successfully applied to determine LST K in pharmaceutical formulations.

The absorbance spectrum of 43.38 μm LST (20 μg ml−1) in absence and in presence of increasing concentrations of CTAB (0.01–0.6 mM).Figure optionsDownload as PowerPoint slide