A Sensitive Spectrophotometric Estimation of Nimodipine in Tablets and Injection Using Phloroglucinol

A rapid, simple, and sensitive spectrophotometric method has been described for the determination of nimodipine in bulk drug, tablets, and injection. The proposed method is based on the diazotization of reduced nimodipine with nitrous acid followed by coupling with phloroglucinol to form colored azo dye and showing absorption maximum ( ) at 410？nm. The formed colored azo dye is stable for about more than 2？h. The method obeyed Beer’s law over the concentration range of 0–25？μg/mL and the corresponding molar absorptivity value is ？L/moL/cm. The Sandell sensitivity values limits of detection (LOD) and quantification (LOQ) values have also been reported for the developed method. The accuracy and precision of the method was evaluated on intra- and interday basis; the relative error (%RE) and the relative standard deviation (RSD) were <2.0%. All variables have been optimized and the presented reaction sequence was applied to the analysis of nimodipine in bulk drug, tablets, and injections. The performance of this method was evaluated in terms of Student’s -test and variance ratio -test to find out the significance of proposed method over the reference method. 1. Introduction Nimodipine (NMD), chemically known as isopropyl-2-methoxyethyl-1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridine dicarboxylate (Figure 1), is a dihydropyridine calcium channel blocker that acts by relaxing the arterial smooth muscle. It is known for its preferential action on cerebral blood vessels and its potential cytoprotective effects by reducing calcium influx into nerve cells [1]. Nimodipine has also been used in the other cerebrovascular disorders, such as ischemic stroke, hypertension, and multi-infarct dementia [2]. It increases blood flow to injured brain tissues. It has been officially determined by liquid chromatographic method with UV detection [3]. Figure 1: Structures of NMD. Various analytical methods for the measurement of this compound have been reported. These include HPLC [4], LC-MS-MS [5], LC-MS [6], and GC with electron capture detection [7]. These techniques are highly expensive and not affordable for the routine analysis of dosage forms. Various analytical techniques that have been reported for this drug in therapeutics include atomic absorption spectrophotometry [8], polarography [9], spectrofluorimetry [10], and spectrophotometry [11–16]. Many of the reported methods are time consuming and require expensive experimental setup [4–7], and polarographic methods are less sensitive [9]. Besides, the reported spectrophotometric methods are less sensitive [11–16]