Background Diflunisal (DIF) has analgesic and anti-inflammatory activity. It is a pharmacopeial drug found in the British Pharmacopoeia, and its major pharmacopeial impurity is biphenyl-4-ol (BPL). Objective Diflunisal was not determined before together with BPL. Presence of BPL could significantly affect the dose of DIF in its dosage forms; hence it is crucial to determine DIF and BPL in presence of each other. Methods Thin layer chromatography (TLC) is the first proposed method, where DIF and BPL are separated on silica gel TLC F254 plates. The eluent is toluene–acetone–acetic acid solution (3.5:6.5:1 by volume). Reversed-phase high-performance liquid chromatography (RP-HPLC) is the second suggested method, where mixture of DIF and BPL are separated on C18 (5 µm ps, 250 mm and 4.6 id) column using phosphate buffer pH = 4 (0.05M)–acetonitrile (40:60, v/v). Detection was done at 254 nm in both methods. Results For TLC method, a concentration range of 0.5–3 and 0.3–1.7 µg/band were used, with mean percentage recoveries 100.22% (SD 0.893) and 100.52% (SD 0.952) for DIF and BPL, respectively. RP-HPLC method was carried out over a concentration range of 5–30 and 2–9 μg/mL, with mean percentage recoveries 100.10% (SD 1.259) and 98.88% (SD 0.822) for DIF and BPL, respectively. Conclusion TLC and RP-HPLC methods were successfully applied for determination of DIF and BPL, quantitatively, whether in bulk powder or in pharmaceutical formulations. Highlights Two chromatographic methods were developed and validated according to ICH guidelines for assay of DIF and its pharmacopeial impurity.
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.
A new sensitive, simple, rapid, accurate and precise spectrofluorimetric method for determination of diflunisal and its impurity is developed. Determination of diflunisal is based on first derivative spectrofluorimetric method, while its impurity can be determined by zero order spectrofluorimetric method. Diflunisal was measured at zero-crossing wavelength 394nm (zero crossing point with its impurity) which was selected for quantification of diflunisal. The impurity was measured directly at 334 nm, using 0.05 M phosphate buffer (pH = 9) as solvent. The analytical signal resulting from first derivative and zero order spectra were measured for diflunisal and its impurity, respectively. Linearity was over the range of 0.1-0.9 μg/mL for both with detection limit of 0.02 and 0.03 μg/mL and quantitation limit of 0.07 and 0.09 μg/mL for diflunisal and its impurity, respectively. The proposed method was validated as per ICH guidelines.The accuracy was checked by applying the proposed method for the determination of the drug and its impurity, the mean percentage recoveries were found to be 99.61±0.911 and 100.41±1.373 for diflunisal and its impurity, respectively. RSD values for repeatability testing were 0.268 and 0.569 and for intermediate precision were 0.224 and 0.259 for diflunisal and its impurity, respectively. The proposed method was effectively applied to analysis of studied drug in its tablet formulation. The results obtained by it were statistically compared with the reported method revealing high accuracy and good precision.
Background Rebamipide (REB) is quinolinone derivative compound, which is used for treatment of stomach ulcers. Objective Four Spectrophotometric methods are developed for quantification of REB and its impurity and degradation product; the debenzoylated isomer of Rebamipide (DER). Methods Method A is ratio difference spectrophotometry (RD) 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 (DD1), where peak amplitude of first derivative of ratio spectra at 261 and 350.2 nm for REB and DER, respectively, are determined. Method C is a second derivative (D2) approach, which allows quantification of both REB and DER at 337 and 340 nm, respectively. Method D is mean centring of ratio spectra (MC), where electronic absorption spectra of REB and DER were recorded and divided by a suitable divisor from DER and REB, respectively, and then mean centre is represented by ratio spectrum so obtained. Results The proposed methods are simple, selective, and sensitive in the quantification of the REB and DER. These methods were validated according to ICH guidelines. Statistical analyses performed on the findings from suggested methods and those obtained from reported method revealed high accuracy and good precision. Conclusion The developed and validated methods are useful methods for quality control assay in routine analysis. Highlights First derivative, second derivative, derivative ratio and mean centring methods for quantification of REM and DER. These methods are useful for analysis of REB in pharmaceutical dosage form.
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