Magda Y. El-Mammli

Spectrophotometric determination of flucloxacillin in pharmaceutical preparations using some nitrophenols as a complexing agent.

Some nitrophenols are proposed as chromogenic reagents for the spectrophotometric determination of flucloxacillin. The reagent forms a greenish yellow 1:1 complex with flucloxacillin at pH 9.0. This complex is stable for at least 3.0 h after its formation. The greenish yellow charge transfer complex species has an absorption maximum at 446, 435, 442, 473 and 439 nm for p-nitrophenol (I), 2,4-dinitrophenol (II), 3,5-dinitrosalycilic acid (III), picramic acid (IV) and picric acid (V), respectively, with a molar absorptivity between 1.43 x 10(4) and 2.59 x 10(4) l mol(-1) cm(-1). Beers low is valid over the concentration range 2.0-40 microg ml(-1) of flucloxacillin. The detection and quantitation limits as well as relative standard deviation were also calculated. The reagents have been successfully used for the spectrophotometric determination of flucloxacillin in pure form and in pharmaceutical preparations.

Determination of certain antihistamines through ternary complex formation

Abstract Antihistamines, namely terfenadine and chlorphenoxamine hydrochloride, react with cobalt and toxiocyanate ions to give ternary complexes. These complexes are readily extractable in benzene to give a blue colour with maximum absorption at 625nm. which can be used for Quantitative spectrophotometric analysis. The mean recoveries for authentic samples of terfenadine and chlorphenoxamine hydrochloride were 99.9 ± 0.3 S.E. and 99.9 ± 0.3 respectively (P = 0.05). Alternatively, determination of cobalt content of the benzene extract via atomic absorption spectroscopy provides an indirect method for the determination of these antihistamines. The mean recoveries were 99.33 ± 0.3 and 99.19 ± 0.3 respectively. Both methods were applied to the analysis of pharmaceutical preparations, the results obtained agreed well with those obtained by official methods.

Assessment of matrix effects and determination of niacin in human plasma using liquid–liquid extraction and liquid chromatography–tandem mass spectrometry

A simple, sensitive and rapid liquid-liquid extraction method for the analysis of nicotinic acid (niacin) and its labeled internal standard nicotinic acid-d4 (niacin-d4) in human plasma was developed and validated. The analyte and its internal standard were isolated from acidified plasma using a single liquid-liquid extraction procedure with methyl-t-butyl ether. The extracted samples were analyzed by liquid chromatography-tandem mass spectrometry in positive electrospray ionization mode with multiple reaction monitoring. The calibration curves were linear in the measured range between 5 and 1000 ng/mL and the limit of detection was calculated as 122 pg/mL. The method required 250 microL of human plasma and the total run time between injections was 3.5 min. Matrix effects were assessed by post-column infusion experiments, phospholipids monitoring and post-extraction addition experiments. The extraction of phospholipids and niacin from plasma was studied under acidic, neutral and basic conditions. Acidic conditions were optimal for both the recovery of niacin and the removal of phospholipids; the degree of matrix effects for niacin was determined to be 2.5%. It was concluded that effective removal of matrix components can overcome low recovery issues associated with liquid-liquid extractions of polar analytes.

New Spectrophotometric and Conductometric Methods for Macrolide Antibiotics Determination in Pure and Pharmaceutical Dosage Forms Using Rose Bengal

Two Simple, accurate, precise, and rapid spectrophotometric and conductometric methods were developed for the estimation of erythromycin thiocyanate (I), clarithromycin (II), and azithromycin dihydrate (III) in both pure and pharmaceutical dosage forms. The spectrophotometric procedure depends on the reaction of rose bengal and copper with the cited drugs to form stable ternary complexes which are extractable with methylene chloride, and the absorbances were measured at 558, 557, and 560 nm for (I), (II), and (III), respectively. The conductometric method depends on the formation of an ion-pair complex between the studied drug and rose bengal. For the spectrophotometric method, Beers law was obeyed. The correlation coefficient () for the studied drugs was found to be 0.9999. The molar absorptivity (), Sandell’s sensitivity, limit of detection (LOD), and limit of quantification (LOQ) were also calculated. The proposed methods were successfully applied for the determination of certain pharmaceutical dosage forms containing the studied drugs

Development of a Liquid Chromatography-Negative ESI-Tandem Mass Spectrometry Method for Ibuprofen with Minimization of Matrix Effects Associated with Phospholipids

Abstract Phospholipids are known to cause matrix ionization effects during LC/MS/MS analysis of biological samples. Matrix effects involving endogenous phospholipids in the negative ESI mode have been investigated in this work for the determination of ibuprofen in human plasma. Glycerophosphocholines (GPChos) and 2-lysoglycerophosphocholines (2-lyso GPChos) were monitored as markers for endogenous matrix components. Various extraction solvents were evaluated to assess their abilities to remove phospholipids from plasma samples to minimize matrix effects. Post-column infusion experiments were applied to chromatographically resolve matrix effects that resulted from endogenous phospholipids. The resulting method was validated and linearity was obtained over a concentration range of 50 to 10,000 ng/mL.

Validated Stability-Indicating Methods for Determination of Mometasone Furoate in Presence of its Alkaline Degradation Product

Two novel stability-indicating TLC densitometric and chemometric methods were developed for the determination of mometasone furoate (MF) in the presence of its alkaline degradation product (MF Deg). The developed TLC densitometric method (Method A) is based on the quantitative densitometric separation of MF from its alkaline degradation product on silica gel 60 F254 and measurement of the bands at 250 nm. The separation was carried out using hexane-chloroform-methanol-acetonitrile (6:6:1:0.3, by volume) as a developing system. A well-resolved and compact bands for (MF) and (MF Deg) at retention factors 0.36 and 0.66, respectively. Good resolution between (MF) and (MF Deg) assured the specificity of the proposed method. The method showed good linearity in the concentration range 0.5-5 μg/band with r2 = 0.9998. The method validation was performed according to ICH guidelines demonstrating to be accurate, precise, robust and sensitive. The LOD and LOQ were found to be 0.21 and 0.63 μg/band for MF, respectively. The developed TLC-densitometric method can be applied for identification and quantitative determination of MF in bulk drug and pharmaceutical dosage forms without any interference from excipients and degradates. Method B is a multivariate chemometric-assisted spectrophotometry, where classical least squares, principal component regression and partial least squares were applied. Statistical analysis of the results has been carried out revealing high accuracy and good precision.

Spectrophotometric Determination of Desloratadine, Fexofenadine HCL, Etodolac, Moexipril HCL and Thiocolchicoside in Pure and Pharmaceutical Formulations

Desloratadine (I), an orally active major metabolite of the nonsedating antihistamine loratadine, is a selective, potent, peripheral H1 receptor antagonist1. Very few visible spectrophotometric methods have been described for determination of Desloratadine2,3. To analyze this drug in tablets, reversed-phase column liquid chromatography4-7 and gas chromatography8 techniques have also been described.

Application of Cobalt (II)-EDTA Complex as a Reductant for Molybdophosphoric Acid Used for the Spectrophotometric Assay of Aciclovir, Fluconazole, Ramipril and Secnidazole

A new spectrophotometric method has been described for the assay of aciclovir, fluconazole, ramipril and secnidazole based on formation of insoluble molecular complexes with molybdophosphoric acid (MPA) under acidic conditions. As a second step, a colour reaction has been combined to determine MI’A, released from the complex (and the studied drugs in turn), using a chromogenic reductant; cobalt (Ⅱ)-EDTA complex to produce molybdenum blue Mo(subscript 5+). The colour of the produced Mo(subscript 5+) is measured at 700-710 nm. Appropriate conditions were established for the precipitation and the colour reactions to obtain maximum sensitivity. Under the proposed conditions, this method is applicable over concentration range of 40-580μg ML^(-1). The results demonstrated that the proposed method is equally accurate, precise and reproducible as the official or reported methods thus it is recommended for quality control and routine analysis where time, cost effectiveness and high specificity of analytical techniques are of great importance.