Spectrofluorimetric Quantification of Furazolidone and Nitrazepam in Tablet Formulations – Development of Sensitive Fluorescence Techniques for Non Fluorescent Drugs by Quenching Approach.

Fluorescence is a photoluminescence process in which atoms or molecules are excited by absorption of electromagnetic radiation. The excited species then relax to the ground state, giving up their excess energy as photons. One of the most attractive features of molecular fluorescence is its inherent sensitivity, which is often one to three orders of magnitude better than absorption spectroscopy .For selected species under controlled conditions, single molecules have been detected by Fluorescence spectroscopy. Another advantage is the large linear concentration range of fluorescence methods, which is significantly greater than those encountered in absorption spectroscopy. An electronically excited molecule, that does not undergo any chemical reaction, has to get rid of its excess energy in order to return to the ground state. The ways of energy release are divided in to two categories; Radiative and non-radiative transitions according as energy is released as light. The energy of the emitted radiation is usually lower than the excitation energy since in solution the energy resulting in vibrational excitation is rapidly absorbed by the solvent. When the molecules arrives at the lowest vibrational level and the solvent is not capable of accepting such a big quantum of energy as would be necessary in order to return to the ground state, the energy is emitted as photons. Furazolidone and Nitrazepam were selected for the indirect fluorimetric determination. Furazolidone is official in IP, BP, and USP. Determination of furazolidone in official method is based on the measurement of absorbance in aqueous DMF at 367nm and use of specific extinction coefficient value. Literature review reveals that, different technique such as second-derivative spectrophotometry, quenchofluorimetric methods, ELISA and chromatographic methods like HPLC and GC have been utilised for the determination of furazolidone in formulations and in biological matrix. Nitrazepam is official in IP and in BP. Pharmacopoeial methods use UV spectrophotometric method, absorbance being measured at 280nm in methanolic HCl medium. The literature survey reveals that, different analytical techniques for the determination of nitrazepam in pure form, formulated drugs and the drug in biological samples by PCFA, UV, colorimetric method, chromatographic methods such as HPLC, GC and hyphenated techniques like LC-MS, UPLC- MS/MS are available. Furazolidone and nitrazepam were selected for the quenchofluorimetric determination. It is an indirect spectrofluorimetric method. The method has been found to be sensitive one, as the technique is being a type of spectrofluorimetric method These developed methods could be used in establishing the quality control of furazolidone tablet and nitrazepam tablet