Case Study on Spectrophotometric Methods for the Determination of Nimodipine in Pure and in Pharmaceutical Preparations

Spectrophotometry as an Analytical Method

Infrared spectrophotometry: 700-15000nm wavelength

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Ultraviolet spectrophotometry: 200-700nm wavelength

Some of the advantages of using spectrophotometry as an analytical method include it being fast, accurate and simple to perform, hence bulk tests of drugs can be done accurately using this method.

Apparatus Used

Digital spectrophotometer

Reagents

Distilled water, sulfamic acid, NaOH, HCl, acetylacetone, pure nimodipine and a standard solution.

Procedure

Add equal amounts of nimodipine into test tubes.

Add 1M HCl to each of the tubes.

Add 4M NaOH after waiting for one minute each.

Measure the mixture using the spectrophotometer at a wavelength of 440nm against the standard.

Findings

Maximum absorbance of 0.25 against a wavelength of 440nm is recorded.

Discussion

According to Beers law, the sensitivity and different absorbance can be attributed to, the reagents, alkali, acid and reaction time given. A linear relationship is reported between the concentrations of nimodipine and the wavelengths by the spectrophotometer.

As for the reagents, the effect was determined by measuring various absorbance measurements at various wavelengths. Decolorization of the dyes were noted to result from increased alkali concentrations. A Sandell sensitivity of 0.0549 was noted.

It is also logical to note that a linear relationship is always seen between the concentration of drugs and absorbance of the same.

Chromatographic Methods

Chromatography is a technique of separation of different substances based on their different rates of adsorption in a given medium. It involves the elution of an analyte in which an eluent enters a column, exiting in its pure form. The affinity of the molecule is measured by its solubility, as well as adsorption. The relationship between adsorption and molecular movement is inverse, whereas that of solubility and motion is directly proportional.

This method is conventionally used to separate pure substances when isolating drug components, as well as poisons and dyes.

Various types of chromatography exist, such as, liquid chromatography, paper chromatography, size exclusion, thin layer, ion exchange, gas and affinity chromatography. In this assay, the liquid chromatography was used.

L-nimodipines chromatographic methods is based on absorbance and crystallization. In any chromatographic assay, there must be a solvent and an anti-solvent. In this case, the reagents used were acetone and deionized water respectively.

Following the assay, a series of optimum conditions were established. These are:

150mg/Ml Acetone-nimodipine concentration.

Antisolvent-solvent ratio equal to 3.

A particle flow rate of 9Ml/minute.

15 degrees Celsius temperature.

0.2% surfactant.

It was evident that precipitation temperature did not really have a huge effect on the chromatography.

The scientific implications of these studies is that a nimodipine tablet is bound to have high bioavailability, and therefore be a very potent calcium channel blocker.

References

Revanasiddappa, H. D., Mallegowda,S. M., Vinay, K. B. (2011). Spectrophotometric methods for the determination of nimodipine in pure and in pharmaceutical preparations. Jordan Journal of Chemistry.