Determination of Ofloxacin in Tablets by Room-Temperature Phosphorimetry on a Poly(vinyl alcohol) Solid Substrate.

Abstract

Solid substrate room-temperature phosphorimetry (SS-RTP) is widely known as a sensitive and simple analytical technique for determination of trace amounts of organic compounds. Among the utilizable substrate materials, filter paper is the most commonly used. Filter paper does, however, have some drawbacks; e.g., it has considerable background emissions, the removal of which requires labor-intensive treatment, and continuous dry gas flow through the sample compartment of the spectrophotometer is necessary during measurement of RTP emissions because moisture and oxygen can quench emissions of the analytes. To overcome these drawbacks, we have investigated and report herein on a new solid substrate prepared from poly(vinyl alcohol) (PVA).1) The best feature of this substrate is that it does not require any dry gas flush of the sample compartment during RTP measurement because the RTP intensity is very stable, even with atmospheric exposure. Furthermore, PVA has negligibly weak background emissions.2)The presence and/or amount of ofloxacin (OFLX), a new synthetic quinolone antibiotic with a broad spectrum of activity against gram-positive and gram-negative bacteria, is detected primarily by methods of fluorimetry and spectrophotometry, which are easily carried out. [3][4][5][6][7] Up to now, the most common technique for the determination of OFLX in pharmaceutical tablet has been based on HPLC with fluorescence or UV detection. [8][9][10] However, these methods need comparatively large amounts of sample solution. In order to develop a micro and trace analysis of OFLX by an easy method, we applied the PVA-substrate RTP to the analysis of OFLX. ExperimentalMaterials and Reagents PVA, degree of polymerization 2000 and degree of hydrolysis 78-82 mol% (Kanto Chemical); OFLX (Sigma); sodium hydroxide, extra-pure grade (Kanto Chemical); thallium(I) nitrate, extrapure grade (Kanto Chemical); and potassium iodide, extra-pure grade (Kanto Chemical), were used as purchased without further purification. Purified distilled water (Milli-Q, Millipore) was used as the solvent.Solutions The solutions for the RTP measurement were prepared as follows. Stock solutions of OFLX were prepared in water or an aqueous NaOH solution of appropriate concentration. Stock solutions of NaOH, TlNO 3 , and KI were prepared in water. Working solutions of lower concentration were obtained by an appropriate dilution of stock solution with water or the appropriate aqueous NaOH solution.For the UV photometry, a stock solution of OFLX was prepared in water, and working solutions of lower concentration were obtained by appropriate dilution of stock solution with water.For the fluorimetry, a stock solution of OFLX was prepared in a 49.55 mM phthalate buffer solution, and working solutions of lower concentration were obtained by an appropriate dilution of stock solution with the buffer solution.For analysis of the commercial tablet, solutions were prepared as follows. Five tablets were accurately weighed and powdered. An amount of powder equivalent to one ta...