Q-ABSORBANCE RATIO SPECTROPHOTOMETRIC METHOD FOR THE SIMULTANEOUS ESTIMATION OF AMLODIPINE BESYLATE AND CANDESARTAN CILEXETIL IN SYNTHETIC MIXTURE

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ABOUT AUTHORS:
Kotecha B*, Pambhar M, Zala G, Faldu S
Department of Quality assurance, Smt. R.D. Gardi B.Pharmacy College,
Nyara, Rajkot-360 110, Gujarat, India
kotecha_bijal29@yahoo.com

ABSTRACTS:
The present manuscript describe simple, sensitive, rapid, accurate, precise and economical q-absorbance method for the simultaneous determination of Amlodipine besylate and Candesartan cilexetil in synthetic mixture. Absorbance ratio method uses the ratio of absorbance at two selected wavelengths, one which is an Isoabsorptive point at 242 nm in Methanol. The second wavelength is used 255 nm, which is λmax of Candesartan cilexetil in Methanol. The linearity was obtained in the concentration range of 5-25 μg/mlof both drugs. The concentration of drugs was determined by using ratio of absorbance at isoabsorptive point and at the λ-max of Candesartan cilexetil. The method was successfully applied to pharmaceutical dosage form because of no interference. The result of analysis has been validated by recovery studies.

REFERENCE ID: PHARMATUTOR-ART-2156

PharmaTutor (ISSN: 2347 - 7881)

Volume 2, Issue 5

Received On: 11/03/2014; Accepted On: 18/03/2014; Published On: 01/05/2014

How to cite this article: B Kotecha, M Pambhar, G Zala, S Faldu; Q-Absorbance Ratio Spectrophotometric Method for the Simultaneous Estimation of Amlodipine Besylate and Candesartan Cilexetil in Synthetic Mixture; PharmaTutor; 2014; 2(5); 167-178

INTRODUCTION: [3, 11, 12, 14, 15, 16, 19]
Amlodipine besylate (AB) (fig. 1a) is the besylate salt of amlodipine, chemically known as, 2-[(2-aminoethoxy)methyl]-4-(2-chlorophenyl)-1,4-dihydro-6-methyl3,5pyridinedicarboxylic acid3-ethyl, 5-methyl ester (±) monobenzenesulfonate[1]. It is a long-acting, calcium channel blocker. It is used in the treatment of hypertension and anginal [12, 16]. Candesartan cilexetil a potent [4], orally active and selective angiotensin II type 1 receptor blocker, belongs to benzimidazole class with chemical name1-[[(cyclohexyloxy) carbonyl] oxy] ethyl2-ethoxy-1-[[2'(1H-tetrazol-5-yl) [1, 1'-biphenyl]-4yl] methyl]-1H-benzimidazole-7-carboxylate1-3. It is an anti hypertensive drug and is used in treatment of angina. AB is official in USP, BP, EP & IP whereas CC is official in JP [14, 15, and 19]. The chemical structures of AB & CC are shown in Fig. 1.Combination drug products of AB and CC are widely marketed and used in the treatment of hypertension and cardiac disorders [12, 16]. Several analytical methods like UV spectrophotometry, HPLC, HPTLC, UPLC have been reported for estimation of AB & CC by single drug and also by combining with other drugs [9, 10, 17, 20, 23, 25, and 26]. However no method has been reported till date for the simultaneous estimation of AB & CC using the UV spectrophotometric method. The present paper describes the development and validation of two analytical methods for simultaneous estimation of AB & CC by UV spectrophotometry in tablet dosage form; the methods include absorbance ratio method. The proposed methods are optimized and validated as per the ICH guidelines [6].

Fig. 1 Chemical structures of the analytes (1a) AB & (1b) CC [3, 11]

MATERIALS AND METHODS
SITE OF EXPERIMENTATION:
Smt. R. D. Gardi B. Pharmacy College, Nyara, Rajkot

INSTRUMENTATION:UV visible spectrophotometer Helios Alpha, Thermo Scientific, (model UV A 1002E) with 1 cm matched quartz cells were used for all absorbance measurements. Contech, EIE instrument pvt. Ltd. (model CA 34) balance was used for weighing the samples.

REAGENTS: Double distilled water and Whatmann filter paper (0.45μm) were used for filtration. Active pharmaceutical ingredient (API) working standards of amlodipine besylate (AB), candesartan cilexetil (CC) were obtained as gift sample from Alembic Pharma limited, Baroda, India and test samples (tablets with composition CC-8 mg and AB (equivalent to amlodipine-5 mg) were procured from the local market.

CHEMICAL: Methanol obtained from Chemdyes co. Rajkot.

FOR Q-ABSORPTION RATIO METHOD [2, 5, 8, 13]
Mode
: Scan
Scan speed
: Intelli scan
Wavelength range
: 200 - 400 nm
Absorbance scale
: 0.00 - 2.00 A
Initial base line correction
: Methanol [27]

PREPARATION OF STANDARD SOLUTION IN METHANOL

(A)Amlodipine besylate standard stock solution: (1000 μg/ml)
A 100 mg of Amlodipine besylate was weighed and transferred to a 100 ml volumetric flask. Mix with half quantity of Methanol and volume was made up to the mark.

Amlodipine besylate working standard solution: (100 μg/ml)
Pipette out 10 ml from the standard stock solution in other 100 ml volumetric flask and volume was made up to the mark with Methanol.

(B)Candesartan cilexetil standard stock solution: (1000 μg/ml)
A 100 mg of Candesartan cilexetil was weighed and transferred to a 100 ml volumetric flask. Mix with half quantity of Methanol and volume was made up to the mark.

Candesartan cilexetil working standard solution: (100 μg/ml)
Pipette out 10 ml from the standard stock solution in other 100 ml volumetric flask and volume was made up to the mark with Methanol.

PREPARATION OF SYNTHETIC MIXTURE [21, 22, 28]
The synthetic mixture of Candesartan cilexetil and Amlodipine besylate was prepared in ratio of 8:5. Accurately weighed 8 mg of Candesartan cilexetil and 5 mg of Amlodipine besylate were transferred to 100 ml volumetric flask, and 70 ml of Methanol was added. Excipients, such as Mannitol, glycerol, povidone, Mg-stearate and corn starch which were used in tablet formulation, were added in this mixture and mechanically stirred for 20 minutes. This solution was filtered through the Whatmann filter paper No. 41 and filtrate was collected. Residues were washed with Methanol. The volume of filtrate and washing was combined and volume was made up to 100 ml with Methanol.

PROCEDURE FOR DETERMINATION OF WAVELENGTH FOR MEASUREMENT
1.5 ml of working standard stock solution of AB (100 μg/ml) and 1.5 ml of working standard stock solution of CC (100 μg/ml) were pipetted out into two separate 10 ml volumetric flask and volume was adjusted to the mark with Methanol to get 15 μg/ml of AB and 15 μg/ml of CC. Each solution was scanned between 200 - 400 nm against Methanol as a reagent blank. Isoabsorptive point was selected from the overlay spectra of AB and CC.

PREPARATION OF CALIBRATION CURVE

(A) Calibration curve for AB
Calibration curve for AB consists of different concentrations of standard AB solution ranging from 5 - 25 μg/ml. The solutions were prepared by pipetting out 0.5, 1, 1.5, 2.0, and 2.5 ml of the working standard solution of AB (100 μg/ml) into series of 10 ml volumetric flasks and the volume was adjusted to mark with Methanol. The absorbance of the solutions was measured at 242 nm (λ1) and 255 nm (λ2) against Methanol as a reagent blank. Calibration curve was plotted at both wavelengths and two equations were constructed using the absorptivity.

(B) Calibration curve for CC
Calibration curve for PAM consisted of different concentrations of standard CC solution ranging from 5 - 25 μg/ml. The solutions were prepared by pipetting out 0.5, 1.0, 1.5, 2.0, and 2.5 ml of the working standard solution of CC (100 μg/ml) into series of 10 ml volumetric flasks and the volume was adjusted to mark with Methanol. The absorbance of the solutions was measured at 242 nm (λ1) and 255 nm (λ2) against Methanol as a reagent blank. Calibration curve was plotted at both wavelengths and two equations were constructed using the absorptivity.

VALIDATION OF PROPOSED METHOD [6]

Parameters to be considered for the validation of method are:
A) Linearity and Range

The linearity response was determined by analyzing 6 independent levels of calibration curve in the range of 5 - 25 μg/ml and 5 - 25 μg/ml for AB and CC respectively (n = 3).

The calibration curve of absorbance vs. respective concentration was plotted and correlation coefficient (r2) and regression line equations for AB and CC were calculated.

B) Precision

I) Repeatability
Aliquots of 1.5 ml of working standard solution of AB (100 μg/ml) were transferred to a series of 10 ml volumetric flask. Aliquots of 2.0 of working standard solution of CC (100 μg/ml) were respectively transferred to the same above series of 10 ml volumetric flask. The volume was adjusted up to mark with Methanol to get 15 μg/ml solution of AB and 20 μg/ml solution of CC. The absorbance of solutions was measured spectrophotometrically three times and coefficient of variance (% C.V.) was calculated.

II) Intraday precision
Aliquots of 0.5, 1, and 1.5 ml of working standard solution of AB (100 μg/ml) were transferred to a series of 10 ml volumetric flask. Aliquots of 0.5, 1.0, and 1.5 ml of working standard solution of CC (100 μg/ml) were respectively transferred to the same above series of 10 ml volumetric flask. The volume was adjusted up to mark with Methanol to get 5, 10 and 15 μg/ml solution of AB and 5, 10, and 20 μg/ml solution of CC.

The absorbance of solutions was measured spectrophotometrically three times and coefficient of variance (% C.V.) was calculated.

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