ParacetamolGuaifenesin Oxomemazine Sodium benzoate a b s t r a c tThe aim of the present work was to develop simple, accurate, sensitive and selective methods for the simultaneous determination of oxomemazine (Ox), sodium benzoate (SB), guaifenesin (Gu), andparacetamol (Par). Two methods were described and validated for the simultaneous determination of the four drugs in syrup and suppositories. The first method was a reversed phase HPLC and UVdetection at 220 nm. The assay was performed using C 18 column and an isocratic elution using acetonitrile e methanol e 35 mM KH2PO4 (20: 5: 75; by volume, pH was adjusted to 2.9 ± 0.1) as the mobile phase. The flow rate was 1.5 mL/ min and separation was achieved in less than 15 min. The second method was a TLCspectrodensitometric method, used to separate, identify and quantify the four drugs when present in combination. The drugs were applied on silica gel plates and development was made using methylene chloride-methanol-acetic acid-33% ammonia (89: 8.4: 2: 0.6, by volume) as a mobile phase. The bands of the four drugs were quantified by scanning spectrodensitometricaly at 270 nm. The suggested chromatographic methods were validated and applied successfully to the analysis of the syrup and suppositories.

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A sensitive, accurate and selective high performance thin layer chromatography (HPTLC) method was developed and validated for the simultaneous determination of paracetamol (PAR), its toxic impurity 4-aminophenol (4-AP), pseudoephedrine HCl (PSH) and loratidine (LOR). The proposed chromatographic method has been developed using HPTLC aluminum plates precoated with silica gel 60 F254 using acetone-hexane-ammonia (4:5:0.1, by volume) as a developing system followed by densitometric measurement at 254 nm for PAR, 4-AP and LOR, while PSH was scanned at 208 nm. System suitability testing parameters were calculated to ascertain the quality performance of the developed chromatographic method. The method was validated with respect to USP guidelines regarding accuracy, precision and specificity. The method was successfully applied for the determination of PAR, PSH and LOR in ATSHI(®) tablets. The three drugs were also determined in plasma by applying the proposed method in the ranges of 0.5-6 µg/band, 1.6-12 µg/band and 0.4-2 µg/band for PAR, PSH and LOR, respectively. The results obtained by the proposed method were compared with those obtained by a reported HPLC method, and there was no significance difference between both methods regarding accuracy and precision.

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.

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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.