Y. M. Issa

Ion-selective electrode for the determination of metoclopramide

A metoclopramide (MCP) ion-selective PVC membrane electrode based on the ion-pair complex of MCP with sodium tetraphenylborate was prepared with dioctyl phthalate as a plasticiser. The electrode exhibits a linear response with an approximate Nernstian slope (50 mV decade–1 at 20 °C) within the concentration range 10–1.7–10–5.6M MCP. The effects of ionic strength and pH of the test solution on the electrode performance were studied. The electrode exhibited very good selectivity for MCP with respect to a large number of inorganic and organic cations of biological importance. The standard additions method and potentiometric titration were used to determine the MCP in pure solutions and in pharmaceutical preparations with satisfactory results.

Utility of certain π-acceptors for the spectrophotometric determination of norfloxacin

Simple, rapid, accurate and sensitive spectrophotometric methods are described for the determination of norfloxacin. The methods are based on the reaction of this drug as a π-electron donor with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), 7,7,8,8-tetracyanoquinodimethane (TCNQ), p-chloranil (CL) or chloranilic acid (CLA) as π-acceptors to give highly coloured complex species. The coloured products are measured spectrophotometrically at 460, 843, 550 and 531 nm for DDQ, TCNQ, CL and CLA, respectively. Optimization of the different experimental conditions is described. Beers law is obeyed in the range 10–400 µg ml–1 and colours were produced in non-aqueous media and were stable for at least 3 h. Applications of the suggested methods to representative pharmaceutical dosage forms are presented and compared with the official method. Interferences from additives and common degradation products were investigated.

Spectrophotometric Determination of Ofloxacin and Lomefloxacin Hydrochloride with Some Sulphonphthalein Dyes

Abstract Three spectrophotometric methods for the determination of ofloxacin and lomefloxacin hydrochloride are proposed, which are based on their extraction into chloroform as ion pairs with Bromophenol Blue (BPB), Bromothymol Blue (BTB) and Bromocresol Purple (BCP). The calibration graphs generated were linear over the range 5–25, 2–15 and 2–20 μg ml−1 of drug in chloroform, using three dyes, respectively. The composition of the ion pair was established by continuous variation and molar ratio methods. The described methods were utilized for assaying ofloxacin and lomefloxacin hydrochloride in pharmaceutical preparations.

Conductimetric determination of reproterol HCl and pipazethate HCl and salbutamol sulphate in their pharmaceutical formulations

A simple and sensitive conductimetric method for the determination of salbutamol sulphate and reproterol and pipazethate hydrochlorides is presented based on their ion associates with phosphotungstic and phosphomolybdic acids. The effect of solvent, molar ratio, reagent concentration and temperature were studied, and the solubility products of the formed ion associates were calculated. The method was applied to the determination of the drugs in their pure state or pharmaceutical preparations with mean recovery values of 99.82-100.54, 99.75-100.12 and 99.95-100.40%, and coefficient of variation 0.28-0.52, 0.16-0.36 and 0.19-0.33 for salbutamol sulphate, reproterol HCl and pipazathate HCl, respectively.

Spectrophotometric determination of sildenafil citrate in pure form and in pharmaceutical formulation using some chromotropic acid azo dyes.

Two simple and highly sensitive spectrophotometric methods were developed for the quantitative determination of the drug sildenafil citrate (SC), Viagra, in pure form and in pharmaceutical formulations, through ion-associate formation reactions (method A) with mono-chromotropic acid azo dyes, chromotrope 2B (I) and chromotrope 2R (II) and ion-pair reactions (method B) with bi-chromotropic acid azo dyes, 3-phenylazo-6-o-carboxyphenylazo-chromotropic acid (III), bis-3,6-(o-hydroxyphenylazo)-chromotropic acid (IV), bis-3,6-(p-N,N-dimethylphenylazo)-chromotropic acid (V) and 3-phenylazo-6-o-hydroxyphenylazo-chromotorpic acid (VI). The reaction products, extractable in methylene chloride, were quantitatively measured at 540, 520, 540, 570, 600 and 575 nm using reagents, I-VI, respectively. The reaction conditions were studied and optimized. Beers plots were linear in the concentration ranges 3.3-87.0, 3.3-96.0, 5.0-115.0, 2.5-125.0, 8.3-166.7 and 0.8-15.0 microg mL(-1) with corresponding molar absorptivities 1.02 x 10(4), 8.34 x 10(3), 6.86 x 10(3), 5.42 x 10(3), 3.35 x 10(3) and 2.32 x 10(4)Lmol(-1) cm(-1) using reagents I-VI, respectively. The limits of detection and Sandells sensitivities were calculated. The methods were successfully applied to the analysis of commercial tablets (Vigoran) and the recovery study reveals that there is no interference from the common excipients that are present in tablets. Statistical comparison of the results was performed with regard to accuracy and precision using Students t- and F-tests at 95% confidence level. There is no significant difference between the reported and proposed methods with regard to accuracy and precision.

Spectrophotometric determination of ciprofloxacin in pure form and in tablets through charge-transfer complexation reactions

Three simple, quick and sensitive spectrophotometric methods are described for the determination of ciprofloxacin. The methods are based on the reaction of this drug as ann-electron donor with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), 7,7,8,8,-tetracyanoquinodimethane (TCNQ) andp-chloranil (CL) as π-acceptors to give highly coloured complex species. The coloured products are quantitated spectrophotometrically at 460, 843 and 550 nm for DDQ, TCNQ and CL, respectively. Optimization of the different experimental conditions is described. Beers law is obeyed in the concentration ranges 5–50, 1.5–15 and 20–200 μg ml−1 ciprofloxacin, but the concentration ranges for best accuracy are 10–48, 2.5–15 and 35– 195 μg ml−1 of drug for DDQ, TCNQ and CL, respectively. The relative standard deviations are less than 1.5%. Applications of the suggested methods to ciprofloxacin tablets are presented and compared with the USP method. The stability constants of the 1∶1 DDQ and CL complexes were 1.086 × 104 and 2.581 × 104 lmol−1, respectively, whereas for the 1∶2 TCNQ complex it was 3.62 × 1081. mol−1.

Application of Ion-Pairs in Pharmaceutical Analysis. Atomic Absorption Spectrometric Determination of Promazine, Chlorpromazine, Promethazine, Imipramine and Ciprofloxacin Hydrochlorides with Sodium Cobaltinitrite

ABSTRACT Ion-association complexes of promazine HCl (I), chlorpromazine HCl (II), promethazine HCl (III), imipramine HCl (IV) and ciprofloxacin HCl (V) with [Co(NO2)6]3− were precipitated at their optimum conditions of pH and ionic strength (NaCl-HCl/NaOH) and the excess unreacted cobalt complex was determined using atomic absorption spectrometry (AAS). The applicability of the method for determination of the above drugs in pure solution, pharmaceutical preparations and urine was examined. The drugs can be determined in the ranges 0.485-4.854, 1.619-16.197, 1.441-14.410, 1.415-14.154 and 0.578-5.787 mg/25 ml of I, II, III, IV and V, respectively, with mean relative standard deviations 1.05-1.53% and recovery values of 98.85±0.31-100.09±0.54% indicating high precision and accuracy. The sensitivities of the proposed method were 11.73, 23.00, 30.00, 38.00 and 12.69 μg/ml for the drugs I, II, III, IV and V, respectively; and the detection limits for determination of the investigated drugs were 3.10, 7.20, 13....

Spectrophotometric determination of meclozine HCl and papaverine HCl in their pharmaceutical formulations.

A simple, accurate and highly sensitive spectrophotometric method is proposed for the rapid determination of meclozine and papaverine hydrochlorides using chromotrope 2B (C2B) and chromotrope 2R (C2R). The method consists of extracting the formed ion-associates into chloroform in the case of meclozine HCl and into methylene chloride in case of papaverine HCl. The ion-associates exhibit absorption maxima at 536 and 524 nm for C2B and C2R with meclozine HCl and at 540 and 528 nm with papaverine HCl, respectively. Meclozine can be determined up to 4.0 and 2.6 mg ml(-1), using C2B and C2R, respectively, while papaverine can be determined up to 1.68 and 1.37 mg ml(-1), respectively. The effect of acidity, reagent concentration, time, solvent and stoichiometric ratio of the ion-associates were studied. The molar absorptivity and Sandell sensitivity of the reaction products were calculated. The method was applied to the determination of the drugs in their pure state or pharmaceutical preparations with mean recovery values of 99.63-100.80 and 99.75-100.08% and coefficient of variation 0.945-2.210 and 1.020-1.268 for meclozine HCl and papaverine HCl, respectively.

Colorimetric determination of amoxycillin in pure form and in pharmaceutical preparations

A simple and selective method for the determination of amoxycillin in pure form and in pharmaceutical preparations is described. The procedure is based on the reaction of amoxycillin with 4-nitrophenol (I), 2,4-dinitrophenol (II), 3,5-dinitrobenzoic acid (III) or 3,5-dinitrosalicylic acid (IV) in alkaline medium. The method has been used for the determination of 1-24 mug/ml of amoxycillin trihydrate in solution. The method is selective for the determination of amoxycillin in the presence of its degradation products, other antibiotics and different amines that are normally encountered in dosage forms.

Spectrophotometric Determination of Trimethoprim in Pure Form and in Pharmaceutical Preparations using Bromothymol Blue, Bromocresol Green and Alizarin Red S

ABSTRACT Simple, sensitive and selective methods for the determination of trimethoprim (TMP) in pure form and in pharmaceutical formulations are described. The methods are based on the reaction of TMP as a π-electron donor with bromothymol blue (BTB), bromocresol green (BCG) and alizarin red S (ARS) as electron acceptors. The coloured products are quantified spectrophotometrically at their corresponding λmax. Beers law is obeyed in case of BTB in the range 2.9-23.2 μg/ml (CHCl3), 2.9-20.0 μg/ml (CH2Cl2) and 5.0-29.0 μg/ml (ClC6H5), in the case of BCG 2.9-27.5 μg/ml (H2O/alc.), 2.9-18.3 μg/ml (CHCl3) and 2.9-20.3 μg/ml (CH2Cl2) and for ARS in the range 3.0-12.0 μg/ml in H2O/alc medium. The specific absorptivities, molar absorptivities, Sandell sensitivities, standard deviations and percent recoveries are evaluated. Application of the suggested methods to dosage forms is presented and compared with the pharmacopoeial method. The interference from additives and sulfa compounds, especially sulfamethoxazole, ...