European Journal of Biomedical and Pharmaceutical Sciences

“SOLID AS SOLVENT”- NOVEL SPECTROPHOTOMETRIC ANALYSIS OF METRONIDAZOLE TABLETS USING PHENOL AS SOLVENT

R K Maheshwari, Pramod Vamoriya*, Aparajit Joshi, Shraddha Kori

ABSTRACT

Commonly used organic solvents for spectrophotometric analysis of water insoluble drugs include methanol, ethanol, chloroform, benzene, dichloromethane, dimethyl formamide, acetonitrile, ethyl acetate, toluene, carbon tetrachloride, acetone, hexane etc. The main drawbacks of organic solvents include high cost, toxicity and pollution. Organic solvents have innumerous adverse effects caused by single exposure like dermatitis, headache, drowsiness, nausea, eye irritation and long term exposure causes serious effects such as neurological disorders, chronic renal failure, liver damage, necrosis, mutagenesis disorder. They should be replaced by other eco-friendly alternative sources. The present investigation is an attempt to show that solids can also be wisely used to act as solvent precluding the use of organic solvents. In a separate study, Maheshwari has attempted soxhelation using phenol as solvent. The vapours of boiling phenol got condensed in extraction chamber to effect the extraction of active constituents from powder of crude drugs. The main objective of the present study is to demonstrate the solvent action of solids. Solid excipients can nicely be employed as solubilizers in the development of pharmaceutical dosage forms, in solution form, of poorly soluble drugs (mixed solvency concept). Present study describes the application of solvent character of melted phenol (at 50-60°C) for spectrophotometric estimation of metronidazole in tablets. Solubility of metronidazole in distilled water is 7.28 mg/ml at room temperature. More than 400 mg of metronidazole dissolves in one gram of melted phenol (at 50-60°C). In the present investigation, melted phenol (at 50-60°C) was utilized to extract out (dissolve) the drug from fine powder of metronidazole tablets. Distilled water was used for dilution purpose. Absorbances of standard solutions containing 5, 10, 15, 20 and 25 μg/ml of drug were noted at 320 nm against reagent blanks to obtain calibration curve. Proposed method is novel, economic, eco-friendly, rapid, free from toxicity of organic solvent, accurate and reproducible. Recovery studies and statistical data proved the accuracy, reproducibility and precision of the proposed method. The presence of tablet excipients and phenol did not interfere in the spectrophotometric estimation at 320 nm. Phenol does not interfere above 300 nm in spectrophotometric analysis.

Keywords: Mixed-solvency concept, metronidazole, phenol, spectrophotometric analysis.