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Bull. Pharm. Sci., Assiut University, Vol. 29, Part 1, June 2006, pp. 33-58. SPECTROPHOTOMETRIC AND SPECTRO- FLUORIMETRIC DETERMINATION OF CERTAIN DIURETICS IN PURE FORMS AND IN THEIR PHARMACEUTICAL FORMULATIONS Michael E. El-Kommos1, Ahmad A. Ahmad2, Hesham Salem3* and Mahmoud A. Omar3 1Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Assiut University, Assiut, Egypt 2Department of Organic Chemistry, Faculty of Science, Minia University, Minia, Egypt 3Department of Analytical Chemistry, Faculty of Pharmacy, Minia University, Minia, Egypt ﺘﻬﺎ ( ، ، ، ، ، ، ، ) . ﻋﻠﻰ ٥٠٠ . ٧٢٠ . ٤- - ٧- ﻟﺼﻔﻴﺎ ٤٧٠ . ، ٥٣٥ . Three Simple and selective spectrophotometric and spectrofluorimetric methods were developed for the quantitative determination of certain diuretics (bendroflumethiazide, benzthiazide, chlorthalidone, clopamide, hydrochlorothiazide, hydroflumethiazide, indapamide and xipamide) in pure forms as well as in their pharmaceutical formulations through their hydroxamate formation and subsequent complexation with iron (method I), reaction with potassium ferricyanide (method II) and ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ Received in 11/9/2005 & Accepted in 12/3/2006 * Corresponding author E-mail address: [email protected] Michael E. El-Kommos, et al. reaction with 4-chloro-7-nitrobenzofurazan (method III). The conditions for different reactions were studied and optimized. The methods have been validated and successfully applied to the analysis of bulk drugs and their tablets with good recoveries ranging from 97.93 (±1.46) to 100.6 (±1.75) for method I, 98.49 (±1.43) to 99.86 (±0.87) for method II, and 98.98 (±1.11) to 99.90 (±0.86) for method III. No interference was observed from common pharmaceutical adjuvants. The results obtained compare well with those of reported methods. INTRODUCTION used for assay of chlorthalidone. The most recent methods for Thiazide diuretics are a major determination of clopamide include class of diuretic agents that have been chromatographic23-25 and spectro- used for over 30 years.1 photometric26 methods. Hydrochloro- Subsequently, drugs that are thiazide has been assayed by pharmacologically similar to thiazide chromatographic,27&28 spectrophoto- diuretics but are not thiazides were metric29&30 and spectrofluorimetric31 developed and are called thiazide-like methods. Hydroflumethiazide has diuretics.2&3 been assayed by chromato- Many analytical procedures have graphic32&33 and spectrophoto- been reported for the determination of metric34&35 methods. The most recent the investigated drugs. The British methods for determination of Pharmacopoeia 1998 adopted an indapamide include chromato- electrochemical method for the graphic,36-38 spectrophotometric39&40 analysis of the studied drugs.4 United and fluorimetric41&42 methods. States Pharmacopoeia USP XXV, Xipamide has been assayed by NFXX describes titremetric, spectro- chromatographic43-45 and spectrophotometric and high performance photometric46 methods. liquid chromatographic methods for In continuation, we wish here to the analysis of the studied drugs.5 develop simple and rapid Bendroflumethiazide has been spectrophotometric and spectro- assayed by chromatographic,6-10 fluorimetric procedures for the spectrophotometric11-13 and fluori- determination of thiazide and metric14&15 methods. Benzthiazide has thiazide-like diuretics suitable for been assayed by chromato- quality control purposes. The graphic,16&17 spectrophotometric18 structures of the studied drugs are and electrochemical19 methods. given in Tables 1 and 2. Chromatographic20&21 and spectro- photometric22 methods have been 34 Table 1: The investigated thiazide EXPERIMENTAL diuretics. H Apparatus R6 N R3 A Perken Elmer UV-VIS 6 5 4 3 7 Spectrophotometer (Tokyo,Japan) 8 1 2 N H2NO2S S H with 1 cm quartz cells was used. TM O O Perkin Elmer luminescence Drug R3 R6 spectrometer model LS 45 (Perkin Elmer instruments, USA) connected H C CF Bendroflumethiazide 2 3 to an IBM computer loaded with the TM Hydrochlorothiazide H Cl FLwinlab application software Hydroflumethiazide H CF3 4.00.02 version was used. C l N CH 2SCH 2 All calculations were carried out 5 4 6 3 7 8 1 2 N on IBM computer using statistical H 2N O 2S S H methods in analytical chemistry O O (SMAC) program, designed by Meier Benzthiazide and Zund.47 Materials and reagents Table 2: The investigated thiazide- Hydroxylamine hydrochloride like diuretics. 17.25 g/100 mL in distilled water (2.5 R Cl 1 M) and Potassium ferricyanide 297.74 mg/100 mL in distilled water H2NO 2S R2 (0.01 M). (Loba Chemi Mumbai, India). Sodium hydroxide 32g/100 Drug R1 R2 mL in distilled water (8.0 M), H O hydrochloric acid 70.4 mL/100 mL in Chlor- distilled water (8.0 M), ferric chloride thalidone H H 3 C H N O hexahydrate 14 g/100 mL (0.1 M), in H C H 3 hydrochloric acid (0.5 M), methanol, Clopa- H 3 C N N ethanol, sodium carbonate, sodium mide H O dihydrogen phosphate, disodium H 3 C C H hydrogen phosphate, perchloric acid, H 3 H 3 C N sulphuric acid, nitric acid, dimethyl- Indapa- N H mide formamide, dimethylsulfoxide, O sodium acetate, phosphoric, boric and citric acids (El-Nasr Co. for H 3 C H pharmaceutical chemicals, Egypt) and N Xipa- H 3 C 4-chloro-7-nitrobenzofurazan (NBD- mide OH Cl) 100 mg/100 mL in ethanol and O 7,7,8,8,-tetracyanoquinodimethane H 3 C (Sigma Chemical Co., St. Louis, MO, USA). 35 Michael E. El-Kommos, et al. Pharmaceutical formulations For procedure II Blokium-Diu® tablets (medical Weigh accurately 20.0 mg of each Union Pharmaceutical Co., Abu drug, dissolve in 4.0 mL methanol in Sultan-Ismailia, Egypt), labeled to a 100-mL volumetric flask and contain atenolol (100 mg) and complete to volume with distilled chlorthalidone (25 mg) per tablet. water (0.2 mg/mL). Brinerdine® tablets (Novartis Pharma S.A.E. Cairo, Egypt) [under licence For procedure III from Novartis Pharma AG., Basle, Weigh accurately 20.0 mg of Switzerland], labeled to contain bendroflumethiazide, hydrochloro- reserpine (0.1 mg), clopamide (5 mg) thiazide and hydroflumethiazide or and dihydroergocristine (0.5 mg) per 40.0 mg of clopamide. Dissolve in tablet. Capozide® tablets (Bristol about 10.0 mL absolute ethanol in Myers-Squibb Pharmaceutical Co., 100-mL volumetric flask and Cairo, Egypt), labeled to contain complete to the mark with the same captopril (50 mg) and solvent. hydrochlorothiazide (25 mg) per tablet. Diurex® tablets (Amriya Procedures Pharmaceutical Co., Alexandria, Procedure I Egypt), labeled to contain indapamide Pure drugs (2.5 mg) per tablet. Epilacton X® Accurately measure 1.0 mL of the tablets (Egyptian Pharmaceutical standard stock solution (0.4 mg/mL) Industries Co. [Epico], Tenth of into a test tube, add 1.0 mL of ramadan city, Egypt), labeled to hydroxylamine hydrochloride and 2.0 contain xipamide (20 mg) and mL of sodium hydroxide, heat for 20 spironolactone (100 mg) per tablet. minutes in a boiling water bath, cool, transfer into 10-mL volumetric flask, Standard solutions wash the test tube two times with For procedure I portions of distilled water each of 1 Weigh accurately 20 mg of each mL and transfer the washings into the drug, dissolve in 4.0 ml methanol in a volumetric flask. Add 2.0 mL of 50-mL volumetric flask and complete hydrochloric acid and 1.0 ml of ferric to volume with distilled water. This chloride hexahydrate. Allow to stand stock solution (0.4 mg/mL) is diluted for 20 minutes at room temperature to contain 0.04 mglmL (in case of (25 ± 5°), then dilute with distilled chlorthalidone), 0.08 mg/mL (in case water to volume and mix well. of clopamide, hydroflumethiazide and Measure the absorbance at 500 nm xipamide) or 0.16 mg/mL (in case of against reagent blank treated benzthiazide, bendroflumethiazide, similarly. hydrochlorothiazide and indapamide). 36 Construction of calibration graphs Construction of calibration graphs Dilute the standard stock solution Dilute the standard stock solution (0.4 mg/mL) quantitatively to give a (0.2 mg/mL) quantitatively to give a series of concentrations, suitable for series of concentrations, suitable for constructing the calibration graphs constructing the calibration graphs (final drug concentration; 0.3-4 (final drug concentration; 2-20 μg/mL). Use 1.0 mL of each solution μg/mL). Use 1.0 mL of each solution for the reaction with hydroxylamine for the reaction with potassium and ferric chloride as directed under ferricyanide as directed under the the procedure for pure drugs. general analytical procedure. Stoichiometry Stoichiometry The stoichiometric ratios were The stoichiometric ratios were determined by Job’s method of determined by Job’s method of continuous variation.48 The stability continuous variation.48 constants for formed chelates were calculated. Stability indicating Procedure III properties of the assay as well as Pure drugs spectroscopic investigation of the Accurately measure 1.0 mL of the products using IR and 1H-NMR standard solution into test tube, add spectroscopy were studied. 1.0 mL of 4-chloro-7-nitrobenzofurazan, heat to 60° for 45 minute in Procedure II water bath, cool, transfer into 10-mL Pure drugs volumetric flask, then dilute with Accurately measure 1.0 mL of the ethanol to the volume and mix well. standard stock solution (0.2 mg/mL) The relative fluorescence intensities into test tube, add 1.0 mL of sodium of the resulting solutions were hydroxide and 1.0 mL of potassium measured at room temperature (25 ± ferricyanide, boil for 45 minutes in 5°) against a reagent blank treated water bath, cool and transfer into 10- similarly at (excitation l max 470 nm mL volumetric flask. Wash the test and emission l max 535 nm). tube two times with portions of distilled water each of 1 mL and Construction of calibration graphs transfer the washings into the Dilute the standard stock solution volumetric flask. Add 1.0 mL of quantitatively to give a series of hydrochloric acid, allow to stand for concentrations suitable for 20 minutes at room temperature (25 ± constructing the calibration graphs (2- 5°), then dilute with distilled water to 12 μg/mL).

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