Saeid F. Belal

Spectrophotometric and spectrofluorimetric estimation of ciprofloxacin and norfloxacin by ternary complex formation with eosin and palladium(II)

Spectrophotometric and spectrofluorimetric methods for the determination of two broad-spectrum fluoroquinolone antibacterials (ciprofloxacin and norfloxacin), either in pure form or in tablets, are described. Both methods are based on the formation of a ternary complex between palladium(II), eosin and the fluoroquinolone in the presence of methyl cellulose, as surfactant. Spectrophotometrically, under the optimum conditions, the ternary complexes showed an absorption maximum at 545 nm, with apparent molar absorptivities of 3.4 x 10(4) and 2.7 x 10(4) 1 mol-1 cm-1 and Sandells sensitivities of 1.01 x 10(-2) and 1.12 x 10(-2) micrograms cm-2 for ciprofloxacin and norfloxacin, respectively. The solution of the ternary complex obeyed Beers law in the concentration range 3-10 micrograms ml-1 for both quinolones. The proposed method was applied to the determination of the two drugs in pharmaceutical tablets. A fluorescence quenching method for the determination of both quinolones by forming this ternary complex was also investigated for the purpose of enhancing the sensitivity of the determination. The results obtained by the application of both procedures and the USP XXIII methods were in good agreement and statistical comparison by means of Students t-test and the variance ratio F-test showed no significant differences between the three methods.

Simultaneous determination of enalapril maleate and hydrochlorothiazide by first-derivative ultraviolet spectrophotometry and high-performance liquid chromatography

Two methods are described for the simultaneous determination of enalapril maleate and hydrochlorothiazide in combined pharmaceutical tablets. The first method depends on first-derivative ultraviolet spectrophotometry, with zero-crossing and peak-to-base measurement methods. The first-derivative amplitudes at 224 and 260 nm were selected for the assay of enalapril maleate and hydrochlorothiazide, respectively. The second method is based on high-performance liquid chromatography on a reversed-phase column using a mobile phase of acetonitrile-water (20:80, v/v) (pH 3.8) with programmable detection at 215 and 275 nm. Both methods showed good linearity, precision and reproducibility. The proposed methods were successfully applied to the determination of these drugs in laboratory-prepared mixtures and in commercial tablets.

Spectrophotometric Determination of Etilefrine Hydrochloride, Prenalterol Hydrochloride and Ritodrine Hydrochloride in pharmaceutical dosage form Through Nitrosation and Subsequent Copper Chelation

Abstract A colorimetric method is proposed for the determination of etilefrine hydrochloride, prenalterol hydrochloride and ritodrine hydrochloride, and their dosage forms. The proposed method depends on nitrosation of the phenolic drugs with sodium nitrite in acidic medium with subsequent chelation by copper (II) ions resulted in the formation of stable red color copper chelate which shows a maximum absorbance at 510, 460 and 520 nm for etilefrine, prenalterol and ritodrine chelate, respectively. The experimental conditions leading to optimum color stability and intensity were studied. The proportions of the reactants and the stability constant for the copper chelates were determined. The copper chelates obey Beers law and their absorbance were used for the determination of the three drugs in their pharmaceutical dosage forms. To confirm the validity of the proposed method, recovery studies were carried out using the standard addition method. At the same time, the results of the applications of the meth...

Spectrophotometric and Spectrofluorometric Determination of Heptaminol and mexiletine in Their Dosage Forms

Abstract Two simple, rapid specific methods were developed for the determination of heptaminol and mexiletine and their dosage forms. The methods are based on the reaction of either heptaminol or mexiletine with acetylacetone-formaldehyde reagent to give a yellow chromophore measurable spectrophotometrically at 344 or 338 nm or flurometrically at 480 nm for heptaminol and mexiletine, respectively. The color was stable for at least 1/2 h. Beers law was valid within a concentration range of 15–30 and 8–20 μg ml−1 spectrophotometrically and 0.2–0.8 and 0.4–1.0 μg ml−1 fluorometrically for heptaminol and mexiletine, respectively.

Novel Validated HPTLC Method for the Analysis of Two Binary Mixtures Containing Tamsulosin Hydrochloride with Antimuscarinic Agents

A validated and selective high-performance thin-layer chromatography (HPTLC) method was developed for the analysis of mixures of tamsulosin hydrochloride (TAM) with either tolterodine tartrate (TOL) or solifenacin succinate (SOL) in bulk drug and in combined dosage forms. The proposed method is based on HPTLC separation of the three drugs followed by densitometric measurements of their spots at 224 nm. Separation was carried out on Merck HPTLC aluminum sheets of silica gel 60 F254 using ethyl acetate-methanol-ammonia (6:4:0.05, v/v) as mobile phase. The linear regression analysis data were used for the regression line in the range of 0.1-0.7, 0.4-4 and 1-6 μg band-1 for TAM, TOL and SOL, respectively. The proposed method was validated and successfully applied for the analysis of their pharmaceutical formulations and laboratory-prepared mixtures containing the two bicomponent combinations. The method was validated and showed good performances in terms of linearity, sensitivity, precision, accuracy and stability.

Spectrophotometric and spectrofluorimetric determination of mesna, acetylcysteine and timonacic acid through the reaction with acetoxymercuri fluorescein

Simple, sensitive and specific spectrophotometric (Method I) and spectrofluorimetric (Method II) methods were developed for the determination of three sulfur-containing drugs: mesna (MSN), acetylcysteine (ACT) and timonacic acid (TMN). The methods are based on the suppressive effect of the drugs on the absorbance and the fluorescence intensity of 2′,7′-bis(acetoxymercuri)fluorescein (AMF) in 0.05 M borate buffer. In Method I the decrease in AMF absorbance was measured at 497 nm, while in Method II the fluorescence quenching of the reagent was measured at λem 520 nm (λex 497 nm). All the experimental parameters affecting this reaction were studied and optimized. The selectivity and the stability-indicating aspect of the methods were confirmed and no interference was detected from the oxidation products of the quantified drugs or from other co-administered drugs. Method I was applicable over the concentration ranges 0.5–3, 0.5–2.75 and 0.25–2.75 μg mL−1 for MSN, ACT and TMN, respectively. The reaction sensitivity was enhanced by Method II where the linearity ranges were found to be 0.6–7.2, 0.7–7 and 0.8–10.4 ng mL−1 for MSN, ACT and TMN, respectively. Both methods were applied for the determination of the three drugs in bulk form and in their pharmaceutical preparations without interference from common excipients. The percentage recoveries were satisfactory and they were statistically compared with those obtained from previously reported methods. Moreover, Method II was extended to analyze the drugs in spiked human plasma, by virtue of its high sensitivity.