Walash et al.: Journal of aoaC InternatIonal Vol. 96, no. 6, 2013 1315 Simultaneous Determination of Floctafenine and its Hydrolytic Degradation Product Floctafenic Acid Using Micellar Liquid Chromatography with Applications to Tablets and Human Plasma MohaMed I. Walash, Fathalla Belal, Nahed el-eNaNy, 1 MaNal eId, and RaNIa N. el-shaheNy University of Mansoura, Faculty of Pharmacy, Department of Analytical Chemistry, 35516, Mansoura, Egypt Received June 11, 2011. Accepted by SW November 13, 2011. 1 Corresponding author’s e-mail: nelenanyl@yahoo.com DOI: 10.5740/jaoacint.11-255 DRUG FORMULATIONS AND CLINICAL METHODS A stability-indicating micellar liquid chromatography (MLC) method was developed and validated for the assay of foctafenine (FLF) in the presence of its degradation product and main metabolite, foctafenic acid (FLA). The analysis was carried out on a CLC Shim-Pack octyl silane (C 8 ) column (150 × 4.6 mm id, 5 µm particle size) using a micellar mobile phase consisting of 0.15 M sodium dodecyl sulfate, 10% n-propanol, and 0.3% triethylamine in 0.02 M orthophosphoric acid (pH = 3). The mobile phase was pumped at a fow rate of 1.0 mL/min with UV detection at 360 nm. The method showed good linearity for FLF and FLA over the concentration ranges of 0.5–25.0 and 0.4–10.0 µg/mL, with LODs of 0.16 and 0.12 µg/mL, respectively. The developed method was successfully applied to the determination of FLF in commercial dispersible tablets, with mean recovery of 98.87 ± 1.37%. Also, the proposed method was specifc for the analysis of FLF in presence of the co-formulated drug thiocolchicoside in laboratory-prepared tablets, with mean recovery of 100.50 ± 1.07%. Statistical comparison of the results obtained by the proposed MLC method with those obtained by a comparison method showed good agreement. Moreover, the method was extended to study the degradation behavior of FLF under different International Conference on Harmonization recommended conditions such as alkaline, acidic, oxidative, thermal, and photolytic. The method was further applied for direct determination of FLA as the main metabolite of FLF in human plasma without prior extraction steps, with mean recovery of 110.50 ± 6.5%. F loctafenine (FLF; Figure 1a), 2,3-dihydroxypropyl N-(8- trifuoromethyl-4-quinolyl) anthranilate, is a nonsteroidal anti-infammatory used in oral doses up to 1.2 g daily for the short-term relief of pain. FLF is absorbed from the gastrointestinal tract; peak plasma concentration is obtained 1 to 2 h after oral administration. Its plasma half-life is about 8 h. It is metabolized in the liver to foctafenic acid (FLA; Figure 1b), which is thought to be responsible for most of the analgesic activity. It is excreted mainly as glucuronide conjugates in the urine and bile (1). A literature survey revealed that a few analytical methods were reported for the determination of FLF either in tablets or biological fuids. These methods include spectrophotometry (2–4), spectrofuorometry (5, 6), polarography (7), LC (8–10), and TLC-densitometry (11). From a QC perspective in the pharmaceutical industry, it is important to develop and validate an analytical method for quantitative analysis of an active pharmaceutical ingredient, QC, and stability testing during pharmaceutical research and development processes (12, 13). International Conference on Harmonization (ICH) guidelines (14) also set a mandatory requirement to develop stability-indicating assays. Micellar liquid chromatography (MLC) is a mode of RP-LC that uses aqueous solutions of surfactants above the critical micellar concentration. This chromatographic system presents some differences with respect to the classical RP chromatography because the stationary phase is modifed by the absorption of surfactant and the mobile phase includes surfactant micelles. This system provides hydrophobic, electronic, and steric sites of interaction for solutes that allow effective separation of compounds of different nature (15, 16). In addition, the solubilization capability of the micellar solutions simplifes the sample preparation step, reduces the consumption of organic solvents, and allows the direct determination of drugs in biological fuids without prior extraction. Many MLC analytical procedures have been developed to determine different kinds of drugs in pharmaceutical preparations and biological fuids (17–20). The aim of this study was to develop a sensitive and accurate MLC method for the quantitative determination of FLF in the presence of its degradation product and main metabolite, FLA. The study was extended to investigate the inherent stability of FLF under different stress conditions such as alkaline, acidic, oxidative, thermal, and photolytic. The developed method was applied to the determination of FLF in its single and combined tablets in the presence of the co-formulated drug thiocolchicoside (TCS). Also, it was applied for direct determination of FLA as the main metabolite of FLF in human plasma without a prior extraction step. Experimental Apparatus (a) HPLC system.—Separations were performed using a Merck (Darmstadt, Germany) Hitachi L-7100 chromatograph Downloaded from https://academic.oup.com/jaoac/article/96/6/1315/5655039 by guest on 26 July 2022