Stability-Indicating Chromatographic Methods for the Investigation of Ritodrine Hydrochloride Stability and Characterization of the Oxidative Degradation Product

Two simple and sensitive chromatographic methods were developed and validated for quantitative determination of ritodrine hydrochloride in presence of its oxidative degradation product. The first method depends on densitomeric determination of thin-layer chromatograms of the intact drug in presence of its oxidative degradate. Excellent separation was achieved at 220 nm using a mobile phase of dichloromethane-methanol-glacial acetic acid (15 : 5 : 0.25, v/v/v). The second was an HPLC method, in which efficient separation was carried out on C18 column (150 × 4.6 × 5 μm) using a mobile phase consisting of water: acetonitrile (70,30, v/v) at a flow rate of 1 mL min-1 and UV detection at 220 nm. Beer's law was obeyed in the range of 0.025-0.3 μg/spot and 5-40 μg mL-1 of the intact drug using the two methods, respectively. The proposed methods were validated according to International Conference on Harmonization guidelines and successfully applied for the determination of ritodrine hydrochloride in bulk powder, laboratory prepared mixtures and pharmaceutical dosage form with good accuracy and precision. The results obtained were compared with those of the reported method and were found to be in good agreement.

Utility of Europium ion characteristic peak for quantitation of Fenoterol hydrobromide and Salmeterol xinafoate in different matrices; application to stability studies

A simple selective luminescent dependent approach was established for quantitation of two selective β₂ agonists namely; Fenoterol hydrobromide (FEN) and Salmeterol xinafoate (SAL). This approach utilizes the capability of the cited drugs to undergo a complexation reaction with Europium ion (Eu³⁺) in the presence of 1,10-phenanthroline as a co-ligand. The resultant complex leads to a hypersensitive transition and enhancement of the Eu³⁺ emission peak at 615nm (279nm excitation). Under the optimized conditions, the rectilinear concentration plots of both drugs were (70-1500ngmL^-1) and (100-2000ngmL^-1) with limit of quantitation 51.3 and 84.4ngmL^-1 for FEN and SAL, respectively. The luminescence properties of the complex and its optimum formation conditions were carefully investigated according to the regulations of ICH and the method was successfully applied in plasma. The good accuracy and selectivity of the suggested method allowed extending the proposed protocol into stability study of the cited drugs.

New enhanced spectrofluorimetric approach for picogram detection of Fenoterol hydrobromide through Von Pechman synthesis of coumarins

A new, specific, precise and very sensitive spectrofluorimetric methodology has been established and approved for determination of Fenoterol hydrobromide (FEN) in its pharmaceutical forms and spiked plasma. The strategy utilized the phenolic nature of FEN and its capacity to undergo Von Pechman synthesis of coumarin. In this study, Fenoterol hydrobromide reacts with ethyl acetoacetate in presence of concentrated sulfuric acid to form an extremely fluorescent coumarin derivative measured at 480 nm (λ_ex: 420 nm). Different reaction variables affecting development and stability of the formed coumarin derivative were precisely examined and enhanced to guarantee greatest sensitivity of the strategy. The recommended procedure was found to obey Beer's law in concentration range of (300-2000) pg mL^-1 with quantitation limit 130 pg mL^-1, revealing high sensitivity of the suggested method. The proposed procedure was completely examined and approved through the ICH guidelines and was efficiently applied for the determination of the cited drug in spiked plasma and its dosage forms.

Highly sensitive HPLC method for the determination of galantamine in human plasma and urine through derivatization with dansyl chloride using fluorescence detector

A new method based on fluorescence derivatization with 5-(dimethylamino) naphthalene-1-sulfonyl chloride (dansyl chloride) was developed for the quantitative determination of galantamine in human plasma and urine using high-performance liquid chromatography. The reaction between galantamine and dansyl chloride was optimally realized in 30 min at room temperature and pH 10.5, with a reagent to galantamine molar ratio of 2.13. The derivative was extracted with dichloromethane, and the extract was dried under a nitrogen stream and dissolved in the mobile phase. Chromatographic analysis was performed with an Inertsil C₁₈ column and a mobile phase comprising 40% acetonitrile and 60% 10 mM o-phosphoric acid, 1.2 ml/min. The injection volume was 20 μl. The derivatives were detected with a fluorescence detector (excitation 375 nm/emission 537 nm). The retention time for the dansyl derivative of galantamine was 16.8 min. Linearity was observed between 125 and 2000 ng/ml in water, urine and plasma. The limit of detection and limit of quantification for the developed method were 6.27-70.99 and 18.81-212.97 ng/ml, respectively. Per cent recovery was calculated as 95.15 for urine and 95.78 for plasma. Interday repeatability values for urine and plasma samples (n = 6) at three different concentrations were calculated as a per cent relative standard deviation of 0.24-0.59 and 0.35-0.56. The corresponding per cent relative standard deviation values for intraday repeatability were 0.13-0.51 and 0.04-0.15, respectively.

Spectrofluorimetric determination of certain adrenergic agonist drugs in their pure forms and pharmaceutical formulations: Content uniformity test application

A new, simple, sensitive and rapid spectrofluorimetric method has been developed for determination of certain adrenergic agonists such as isoxsuprine hydrochloride, ritodrine hydrochloride and etilefrine hydrochloride in their pure forms and pharmaceutical dosage forms. The method depends on micellar enhancement of the native fluorescence of investigated drugs by using 2% w/v sodium dodecyl sulfate (SDS) as an anionic surfactant. The enhanced fluorescence intensity of investigated drugs was measured at 305 nm after excitation at 278 nm. The interaction of studied drugs with SDS was studied, and the enhanced fluorescence intensity was exploited to develop an assay method for the determination of investigated drugs. The relative fluorescence intensity-concentration plots were rectilinear over the range 0.15-3.00 μg ml^-1 , with low quantification limits of 0.132, 0.123 and 0.118 μg mL^-1 for isoxsuprine, ritodrine and etilefrine, respectively. The proposed method was successfully applied for determination of studied drugs in their pharmaceutical formulations. Moreover, the high sensitivity of the proposed method allows performing the content uniformity testing of the studied drugs in their tablets by using the official United States Pharmacopeia (USP) guidelines. Statistical comparisons of the results with those of the reported methods revealed excellent agreement and indicated no significant difference in accuracy and precision.

Selective spectrofluorimetric method for the determination of perindopril erbumine in bulk and tablets through derivatization with dansyl chloride

Background

Perindopril erbumine is an antihypertensive, which belongs to the category of angiotensin-converting enzyme inhibitors (ACE inhibitors) that inhibit the conversion of angiotensin I to angiotensin II.

Methods

A new, selective, and sensitive spectrofluorimetric method was developed for the determination of perindopril erbumine based on the reaction with dansyl chloride in alkaline medium to give a highly fluorescent derivative which was measured at 496 nm after excitation at 340 nm in dichloromethane. The reaction conditions were studied and optimized.

Results

Under the optimum conditions, the fluorescence intensity was linear over a concentration range of 1.0 to 21.0 μg/mL (R 2 = 0.9997) with a detection limit of 0.242 μg/mL. In order to validate the method, the results were compared with those obtained by a high performance liquid chromatography method.

Conclusions

The proposed method was successfully applied to the analysis of perindopril erbumine in pure form and tablets with good precision and accuracy as revealed by t- and F tests. The mechanism of the reaction has also been discussed.