Development and Validation of Four Spectrophotometric Methods for Assay of Rebamipide and its Impurity: Application to Tablet Dosage Form.

BACKGROUND: Rebamipide (REB) is quinolinone derivative compound, which is used for the treatment of stomach ulcers. OBJECTIVE: The development of four spectrophotometric methods for quantification of REB and its impurity and degradation product: the debenzoylated isomer of REB (DER). METHODS: Method A is ratio difference spectrophotometry where 254 and 291 nm were selected for REB and 320 and 355 nm were selected for DER, allowing spectral discrimination for both. Method B is derivative ratio spectrophotometry, where the peak amplitudes of the first derivative of ratio spectra at 261 and 350.2 nm for REB and DER, respectively, are determined. Method C is a second derivative approach, which allows quantification of both REB and DER at 337 and 340 nm, respectively. Method D is mean centering of ratio spectra, where electronic absorption spectra of REB and DER were recorded and divided by a suitable divisor from DER and REB, respectively, and then the mean center is represented by the ratio spectrum so obtained. RESULTS: The proposed methods are simple, selective, and sensitive in the quantification of REB and DER. These methods were validated according to International Conference on Harmonization guidelines. Statistical analyses performed on the findings from the suggested methods and those obtained from reported methods revealed high accuracy and good precision. CONCLUSION: The developed and validated methods are useful for quality control assay in routine analyses. HIGHLIGHTS: First derivative, second derivative, derivative ratio, and mean centering methods for quantification of REM and DER. These methods are useful for analysis of REB in pharmaceutical dosage form.

Separation and Determination of Diflunisal and its Impurity by Two Chromatographic Methods: TLC-Densitometry and HPLC.

BACKGROUND: Diflunisal (DIF) has analgesic and anti-inflammatory activity. It is a pharmacopeial drug found in the British Pharmacopoeia (BP), and its major pharmacopeial impurity is biphenyl-4-ol (BPL). OBJECTIVE: DIF has not previously been determined together with BPL. The presence of BPL could significantly affect the dose of DIF in its dosage forms; hence it is crucial to determine DIF and BPL in each other's presence. METHODS: TLC is the first proposed method, where DIF and BPL were separated on silica gel TLC F254 plates. The eluent was toluene-acetone-acetic acid solution (3.5:6.5:1, v/v). Reversed-phase (RP) HPLC is the second suggested method, where a mixture of DIF and BPL was separated on a C18 (5 µm ps, 250 mm and 4.6 id) column using phosphate buffer pH 4 (0.05 M)-acetonitrile (40:60, v/v). Detection was carried out at 254 nm in both methods. RESULTS: For the TLC method, concentration ranges of 0.5-3 and 0.3-1.7 µg/band were used, with mean percentage recoveries of 100.22% (SD 0.893) and 100.52% (SD 0.952) for DIF and BPL, respectively. The RP-HPLC method was carried out over a concentration range of 5-30 and 2-9 µg/mL, with mean percentage recoveries of 100.10% (SD 1.259) and 98.88% (SD 0.822) for DIF and BPL, respectively. CONCLUSION: The TLC and RP-HPLC methods were successfully applied for the determination of DIF and BPL, quantitatively, whether in bulk powder or in pharmaceutical formulations. HIGHLIGHTS: Two chromatographic methods were developed and validated according to International Council on Harmonization guidelines for the assay of DIF and its pharmacopeial impurity.

TLC-Densitometric and RP-HPLC Methods for Simultaneous Determination of Dexamethasone and Chlorpheniramine Maleate in the Presence of Methylparaben and Propylparaben.

Validated simple, sensitive, and highly selective methods are applied for the quantitative determination of dexamethasone and chlorpheniramine maleate in the presence of their reported preservatives (methylparaben and propylparaben), whether in pure forms or in pharmaceutical formulation. TLC is the first method, in which dexamethasone, chlorpheniramine maleate, methylparaben, and propylparaben are separated on silica gel TLC F254 plates using hexane-acetone-ammonia (5.5 + 4.5 + 0.5, v/v/v) as the developing phase. Separated bands are scanned at 254 nm over a concentration range of 0.1-1.7 and 0.4-2.8 µg/band, with mean ± SD recoveries of 99.12 ± 0.964 and 100.14 ± 0.962%, for dexamethasone and chlorpheniramine maleate, respectively. Reversed-phase HPLC is the second method, in which a mixture of dexamethasone and chlorpheniramine maleate, methylparaben, and propylparaben is separated on a reversed-phase silica C18 (5 µm particle size, 250 mm, 4.6 mm id) column using 0.1 M ammonium acetate buffer-acetonitrile (60 + 40, v/v, pH 3) as the mobile phase. The drugs were detected at 220 nm over a concentration range of 5-50 µg/mL, 2-90 µg/mL, 4-100 µg/mL, and 7-50 µg/mL, with mean ± SD recoveries of 100.85 ± 0.905, 99.67 ± 1.281, 100.20 ± 0.906, and 99.81 ± 0.954%, for dexamethasone, chlorpheniramine maleate, methylparaben paraben, and propylparaben, respectively. The advantages of the suggested methods over previously reported methods are the ability to detect lower concentrations of the main drugs and to show better resolution of interfering preservatives; hence, these methods could be more reliable for routine QC analyses.