M. E. K. Wahba

Validated stability-indicating spectrofluorimetric methods for the determination of ebastine in pharmaceutical preparations

Two sensitive, selective, economic, and validated spectrofluorimetric methods were developed for the determination of ebastine (EBS) in pharmaceutical preparations depending on reaction with its tertiary amino group. Method I involves condensation of the drug with mixed anhydrides (citric and acetic anhydrides) producing a product with intense fluorescence, which was measured at 496 nm after excitation at 388 nm.Method (IIA) describes quantitative fluorescence quenching of eosin upon addition of the studied drug where the decrease in the fluorescence intensity was directly proportional to the concentration of ebastine; the fluorescence quenching was measured at 553 nm after excitation at 457 nm. This method was extended to (Method IIB) to apply first and second derivative synchronous spectrofluorimetric method (FDSFS & SDSFS) for the simultaneous analysis of EBS in presence of its alkaline, acidic, and UV degradation products.The proposed methods were successfully applied for the determination of the studied compound in its dosage forms. The results obtained were in good agreement with those obtained by a comparison method. Both methods were utilized to investigate the kinetics of the degradation of the drug.

Validated stability indicating liquid chromatographic determination of ebastine in pharmaceuticals after pre column derivatization: Application to tablets and content uniformity testing

An accurate, simple, sensitive and selective reversed phase liquid chromatographic method has been developed for the determination of ebastine in its pharmaceutical preparations. The proposed method depends on the complexation ability of the studied drug with Zn2+ ions. Reversed phase chromatography was conducted using an ODS C18 (150 × 4.6 mm id) stainless steel column at ambient temperature with UV-detection at 260 nm. A mobile phase containing 0.025%w/v Zn2+ in a mixture of (acetonitril/methanol; 1/4) and Britton Robinson buffer (65:35, v/v) adjusted to pH 4.2, has been used for the determination of ebastine at a flow rate of 1 ml/min. The calibration curve was rectilinear over the concentration range of 0.3 - 6.0 μg/ml with a detection limit (LOD) of 0.13 μg/ml, and quantification limit (LOQ) of 0.26 μg/ml. The proposed method was successfully applied for the analysis of ebastine in its dosage forms, the obtained results were favorably compared with those obtained by a comparison method. Furthermore, content uniformity testing of the studied pharmaceutical formulations was also conducted. The composition of the complex as well as its stability constant was also investigated. Moreover, the proposed method was found to be a stability indicating one and was utilized to investigate the kinetics of alkaline and ultraviolet induced degradation of the drug. The first-order rate constant and half life of the degradation products were calculated.

Liquid Chromatographic Determination of Roxithromycin: Application to Stability Studies

A simple, stability-indicating, reversed-phase liquid chromatographic method has been developed for the determination of roxithromycin in the presence of its forced alkaline, oxidative and ultraviolet degradation products. Reversed-phase chromatography was conducted using an ODS C18 (150 × 4.6 mm i.d.) column at ambient temperature with ultraviolet detection at 215 nm. A mobile phase consisting of 0.03 M potassium dihydrogen phosphate buffer-methanol (40:60, v/v) adjusted to pH 4.5 was used for the separation of the studied drug and its degradation products at a flow rate of 1 mL/min. The method showed good linearity over the concentration range of 10.0-150.0 µg/mL with a detection limit of 2.5 µg/mL and quantification limit of 8.4 µg/mL. The proposed method was successfully applied for the analysis of roxithromycin in its commercial tablets; the obtained results were favorable compared with those obtained by the official method. Furthermore, content uniformity testing of the studied tablets was also conducted. The method was also utilized to investigate the kinetics of the different degradation products of the drug. The first-order rate constant, half-life time and activation energy of the degradation reactions were calculated.

Simultaneous Liquid Chromatographic Determination of Ebastine with Two Sympathomimetic Drugs Using a Monolithic Column

Ebastine (EBS) has been assayed in its laboratory-prepared co-formulated tablets with either pseudoephedrine hydrochloride (PSU) or phenylephrine hydrochloride (PHR) using isocratic reversed-phase chromatography. Separation was conducted using a 50 mm × 4.6 mm i.d., Chromolith® SpeedROD RP-18 end-capped column at ambient temperature. A mobile phase composed of water:acetonitrile in a ratio of 25:75 having a pH of 3.2, has been utilized at 1 mL/min with UV detection at 254 nm for both EBS and PSU and 274 nm for PHR which in turn increased the sensitivity of the proposed method significantly. Symmetric well-separated peaks resulted in a short chromatographic run; <5 min. The proposed method was subjected to detailed validation procedures and proved to be highly sensitive as shown from limit of quantification values which were 4.7, 39.4 and 10.2 μg/mL for EBS, PSU and PHR, respectively. The proposed method was used to analyze EBS in its laboratory-prepared co-formulated tablets; the obtained results were comparable to those resulting from the reference method.

Validation of a Micellar Liquid Chromatographic Method for Determination of Caffeine and Non-Steroidal Anti-Inflammatories

An accurate, simple, sensitive and selective micellar liquid chromatographic method has been developed for the simultaneous determination of caffeine (CAF) and two non-steroidal anti-inflammatory drugs, namely ibuprofen (IBU) and ketoprofen (KET). The chemometric approach was applied to the optimization of separation of the studied drugs. To optimize their separation, the effect of six experimental parameters on retention was investigated by means of multivariate analysis. Separation was conducted using an ODS C18 (150 × 4.6 mm i.d.) stainless steel column at ambient temperature with UV detection at 260 nm. A mobile phase composed of 40 mM sodium dodecyl sulphate (SDS), 10% 1-propanol and 0.3% tri-ethylamine in 0.02 M phosphoric acid adjusted to pH 3 has been used at a flow rate of 1 mL/min. Regression models were characterized by both descriptive and predictive ability (R(2) ≥ 97.9% and R(cv)(2) ≥ 96.2%) and allowed the chromatographic separation of the drugs with a good resolution and a total analysis time within 15 min. The calibration curves were rectilinear over the concentration ranges of 2.0-25.0, 1.5-15.0 and 1.0-10.0 µg/mL for IBU, KET and CAF, respectively, with detection limits of 1.2, 1.0 and 0.6 µg/mL, and quantification limits of 1.6, 1.2 and 0.8 µg/mL, respectively. The results obtained were in good agreement with those obtained by the comparison method.

Micellar liquid chromatographic method for the simultaneous determination of citalopram hydrobromide with its two demethylated metabolites. Utility as a diagnostic tool in forensic toxicology

Highlightscitalopram and metabolites.post mortem re distribution.micellar liquid chromatography.detailed validation procedure.pharmaceutical applications. Abstract A micellar liquid chromatographic method has been developed for the simultaneous determination of citalopram hydrobromide (CTA) with its two demethylated metabolites namely; desmethyl citalopram hydrochloride (DCTA) and didesmethyl citalopram tartrate (DDCTA). Separation was conducted on a C18 column using a mobile phase composed of 0.18 M sodium dodecyl sulphate (SDS), 15% 1‐propanol, 0.3% tri‐ethylamine, adjusted to pH 4 with 0.2 M o‐phosphoric acid and adopting UV detection at 240 nm. Analysis was performed at 60 °C applying a flow rate of 2 mL/min. The proposed method was linear over the concentration ranges of 1.0–200.0, 0.6–200.0, and 0.5–200.0 &mgr;g/mL for CTA, DCTA, and DDCTA respectively, with corresponding limits of detection (LOD) of 0.5, 0.4, and 0.3 &mgr;g/mL and limits of quantification (LOQ) of 0.8, 0.5, and 0.4 &mgr;g/mL. The method was fully validated which allowed its application for the determination of CTA in its tablets. Moreover, the proposed method was extended to assay CTA with its metabolites in rat tissue organs samples which allowed the method to be used as a diagnostic tool in forensic toxicology.

Novel validated spectrofluorimetric methods for the determination of taurine in energy drinks and human urine

Two sensitive, selective, economic and validated spectrofluorimetric methods were developed for the determination of taurine in energy drinks and spiked human urine. Method Ι is based on fluorimetric determination of the amino acid through its reaction with Hantzsch reagent to form a highly fluorescent product measured at 490 nm after excitation at 419 nm. Method ΙΙ is based on the reaction of taurine with tetracyanoethylene yielding a fluorescent charge transfer complex, which was measured at λex /em of (360 nm/450 nm). The proposed methods were subjected to detailed validation procedures, and were statistically compared with the reference method, where the results obtained were in good agreement. Method Ι was further applied to determine taurine in energy drinks and spiked human urine giving promising results. Moreover, the stoichiometry of the reactions was studied, and reaction mechanisms were postulated.