Abstract
This study is concerned with two sensitive, fast and reproducible approaches; namely, second-derivative synchronous fluorimetry (method I) and reversed phase high-performance liquid chromatography with fluorimetric detection (method II) for synchronized evaluation of losartan (LOS) and amlodipine besylate (AML). Method I is based on measuring second-derivative synchronous fluorescence spectra of LOS and AML at Δλ = 80 nm in water. The experimental factors influencing the synchronous fluorescence of the considered compounds were sensibly adjusted. The chromatographic analysis was executed on a Nucleodur MN-C18 column of dimensions; 250 × 4.6 mm i.d. and 5 µm particle size). The fluorimetric detection was time-programmed at λem = 440 nm for AML (0.0–7.5 min) and at λem = 400 nm for LOS (7.5–10 min) after excitation at λex = 245 nm. The mobile phase is a blend of acetonitrile with 0.02 M phosphate buffer in a proportion of 45 : 55, pH 4.0, pumped using a flow rate of 1 ml min−1. The calibration plots were established to be 0.1–4.0 µg ml−1 for both drugs in method I and 0.05–4.0 µg ml−1 for both drugs in method II. The study was extended to the evaluation of the two drugs in their co-formulated tablets.
Highlights
Losartan potassium (LOS) (2-n-butyl-4-chloro-5-hydroxymethyl-1-[2’-(1H-tetrazol-5-yl) methyl] imidazole) is a highly effective antihypertensive agent acting by antagonizing angiotensin II receptor [1]
The usage of routine fluorescence method for the simultaneous estimation of LOS and AML is difficult, especially if it is required to estimate these compounds in their co-formulated dosage form
The second-derivative synchronous fluorescence spectroscopy (SDSFS) method was selected for concurrent estimation of LOS and AML together in their dosage forms
Summary
Losartan potassium (LOS) (2-n-butyl-4-chloro-5-hydroxymethyl-1-[2’-(1H-tetrazol-5-yl) (biphenyl-4-yl) methyl] imidazole) is a highly effective antihypertensive agent acting by antagonizing angiotensin II receptor (figure 1) [1]. Review of the literature disclosed that spectrophotometric and chromatographic techniques have been used for evaluation of LOS [3,4,5,6], and AML [7,8,9,10] in solitary and multicomponent dosage forms or in biological fluids. The target of the current work is to set up and progress two new, sensitive and selective methods for synchronized evaluation of LOS and AML either in pure form or in pharmaceutical formulations employing derivative synchronous fluorescence spectroscopy (DSFS) (method I) and LC with fluorimetric detection (method II). In authors’ information, neither synchronous spectrofluorimetry nor HPLC with fluorimetric detection were previously used for the synchronized analysis of LOS and AML in their co-formulated dosage forms. Binary mixtures of topiramate and levetiracetam [25], itopride and domperidone [26], nebivolol and amlodipine [27], desloratadine and montelukast sodium [28], AML and valsartan [29], adapalene acidic and oxidative products [30], methocabamol and ibuprofen [31] have been estimated using this technique
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