Sayed M. Hassan

Spectrophotometeric determination of someN-substituted phenothiazine derivatives usingN-bromophthalimide

A simple, rapid and sensitive spectrophotometric method is described for the quantitative determination ofN-substituted phenothiazines. The method depends on the formation of a stable phenothiazine free radical cation by the use ofN-bromophthalimide as oxidising agent in a strong acid medium (methanol/ sulphuric acid 1∶ 1 v/v). The produced red or violet color possesses absorption maximum range from 500 to 530 nm. A linear relationship exists between the absorbance at (λmax) and concentration in the range 5 to 40 μg ml−1 with apparent molar absorptivities range from 6 × 103 to 12 × 1031 mol−1 cm−1. The color is developed instantaneously for all the studied phenothiazines except for thioproperazine mesylate, trifluoperazine dihydrochloride and prochlorperazine mesylate that require 25, 15 and 25 min, respectively, for complete reaction. The developed colors are stable over 24 h. The average % recovery is 99.85±0.61 to 100.28±0.95. The method was applied successfully to the microdetermination of chlorpromazine HCl, promethazine HCl, pericyazine, thioproperazine mesylate, perphenazine, prochlorperazine mesylate, trimeprazine tartrate and trifluoperazine 2HCl either in pure form or incorporated in their pharmaceutical preparations. The results of analysis are in good agreement with those of the official B.P. 1988 and USP XXII.

Spectrophotometric assay of retinol via charge-transfer complexes

Simple and sensitive spectrophotometric methods for the assay of retinol have been presented. The first method was based on the reaction of retinol with iodine to give a molecular charge-transfer complex, the retinol acting as n-donor and iodine as σ-electron acceptor. The second method depends on the formation of a highly coloured stable radical anion between retinol and 7,7,8,8-tetracyanoquinodimethane (TCNQ as a π-electron acceptor. The molecular ratios of the reactants in the complexes have been established and the experimental conditions leading to maximum charge-transfer bands were also studied. Beers law is obeyed over the retinol concentration range 2.5–26 µg/ml. The proposed procedures have been applied successfully to the analysis of drug formulation. The average recovery and average standard deviation was 99.99 ±1.13% with retinol-iodine and 100.001 ± 1.31% with retinol-TCNQ. A kinetic study was performed by heating retinol at 50°C for different periods of time, the result obtained by plotting log c against time indicates that thermal decomposition of retinol is of first order. The results obtained by both methods were in good agreement with those obtained by the official method. The developed procedures were found to be simple, accurate and precise and can be used for the determination of retinol in presence of its degradation products.

Colorimetric Determination of Some N-Substituted Phenothiazine Derivatives Using 2-Iodoxybenzoate

Abstract A new, sensitive colorimetric method has been described for the quantitative determination of six N-substituted phenothiazines. the method depends on the formation of stable phenothiazine free radical by the use of 2-iodoxybenzoate as chromogenic reagent. the drug in 50% sulphuric acid is treated with reagent (5×10−4 M). the produced red or purple color possesses characteristic absorption maximum for each of the drugs tested. Beers law is obeyed over the concentration range 2-30 μg.ml−1 with apparent molar absorptivities ranging from 9.4-12.4×10−3 for the studied phenothiazine derivatives. the average % recovery is 99.5±0.96 - 101.6±1.01. the method was applied successfully to the microdetermination of promazine. HCl, chlorpromazine, HCl, promethazine. HCl, perphenazine, levomepromazine HCl and mesoridazine besylate either in pure form or incorporated in their representative pharmaceutical preparations. the stoichiometry of the reaction was assumed and a reaction mechanism was suggested. the pre...

Colorimetric Determination of Phenols in Water Samples

A colorimetric method for determination of phenols in water has been developed. The method, which is a modification of Liebermanns reaction, uses resorcinol as a chromogenic agent. The developed method is more sensitive, and the difficulties encountered in the widely used 4-aminoantipyrine method have been avoided. Application of both the proposed and 4-aminoantipyrine methods to the analysis of natural and tap water samples are presented.

Polarographic and spectrophotometric determination of isocarboxazid and tranylcypromine sulphate through treatment with nitrous acid

Two methods are described for the determination of two widely prescribed antidepressants, namely isocarboxazid and tranylcypromine sulphate as the pure drugs and in dosage forms. Both methods involve prior treatment with nitrous acid. In the Spectrophotometric method, the two derivatives obey Beers law over the concentration range 1–20 μg/ml. The derivatives are polarographically reducible withE1/2 values of −0.84 and −0.73 V for isocarboxazid and tranylcypromine sulphate, respectively. The calibration plots are linear over the range 4.3 × 10−5−3.0 × 10−4 and 1.1 × 10−5−1.65 × 10−4 mol/1 for isocarboxazid and tranylcypromine sulphate, respectively. The results obtained for assays for the two drugs compare satisfactorily with those given by the official methods.

Spectrophotometric Determination of Pyrithioxin in Pharmaceutical Preparations

Abstract Rapid direct and induced difference spectrophotometric methods for determination of pyrithioxin in single dosage forms (tablets and syrups) are reported. The direct methods depend upon measurement of the absorbance of pyrithioxin in different media at λmax i-e at 296 nm in 0.1 M hydrochloric acid, at 328 nm in citric acid-phosphate buffer of pH 7 and at 314 nm in 0.1 M sodium hydroxide. The mean percentage recovery of the authentic samples were 100.55±0.43, 101.21±0.58 and 100.29±0.64 respectively (P=0.05). The absorbance difference methods are based upon either measurement of the difference between the acid and the alkaline solutions i-e. Δ A (Alk-Acid) at 318 nm with an accuracy of 100.72±0.88 or the absorbance difference between the acid and neutral solutions i-e Δ A (pH 7-acid) at 328 nm with an accuracy of 100.31±0.68.

Diazotised 4-Nitroaniline as a Chromogenic Reagent for the Determination of Indole Derivatives in Certain Pharmaceutical Preparations

Abstract A sensitive colorimetric method has been devised for microdetermination of six indole derivatives; ergotamine tartrate, methylergometrine maleate, dihydroergocornine methanesulphonate, dihydroergocristine methanesulphonate, dihydroergocryptine methanesulphonate and pindolol, both in pure form and in pharmaceutical preparations. The method is based on the reaction of indole moiety with diazotised 4-nitroaniline in buffer solution of pH 6 to produce a stable yellow monoazo dye. Beers law is obeyed over final concentration ranges 8–32 μgm1−1 for ergotamine tartrate, 4–48 μgml−1 for methylergometrine maleate, 8–56 μgml−1 for dihydro-ergot alkaloids and 1–10 μgml−1 for Pindolol with apparent molar absorptivity range (7.62 × 103−2.61 × 104) 1.mole−1.cm−1. A study has been made to determine the optimum conditions of the colour reaction.

Simultaneous High-Performance Liquid Chromatographic Determination of Furazolidone and Nifuroxime in Dosage Forms

Abstract A reversed-phase high-performance liquid chromatographic method for the simultaneous determination of furazolidone and ifuroxime in vaginal suppositories is described. A lichrosorb R.P. 18 (4 × 250 mm) 5 μm column and a mobile phase consisting of methanol-water-buffer pH 3 (40 : 55 : 5) were used. Calibration graphs were rectilinear over the concentration range 1–10 μ/ml for both drugs. Separation was achieved in 12 min. at a wavelength of 350 nm. The proposed method was applied to suppositories containing. the two species, and the results obtained were accurate and precise.

The Spectrophotornetric Determination of Inorganic Phosphate in Egypt Water using Resazurine and Para-rosolic acid

Abstract A sensitive method for rapid determination of inorganic phosphate in water samples is described which is based on a reaction between phosphomolybdate and resazurine; phosphomolybdrlte and p-rosolic acid. The molar absorptivities are 2867.5, 2656.9 at 495 and 470 nm with resazurine and p-rosolic acid reagents. Phosphate can be determirled in concentration range of 0.02 to 0.08 ppm, of 0.02 to 0.16 ppm with resazurine and p-rosolic acid reagents respectively.

pH-Induced Difference Spectrophotometric Methods for Drug Analysis. I. Determination of Indomethacin

Abstract On the basis of the spectral changes of indometnacin induced by changing the pH of the solvent medium, a method for its determination has been developed. The latter involves absorbance measurement of both acid and alkaline solutions of the compound at 260 nm: the difference between both values is linearly related to concentration in the range 0.4-1.4 mg/100 ml. The mean percentage recovery of authentic samples equal 100.1±0.42 (p=0.05). The method has been applied to the analysis of pharnaceutical preparations; the results obtained as compared to those of the official method indicate warranty of application in routine analysis.