Estimation of Clopidogrel bisulphate by Extractive Colorimetric Methods in Bulk and Pharmaceutical Dosage Form

 

Rajan V. Rele

Central Research Laboratory, D.G. Ruparel College, Matunga, Mumbai 400016, Maharashtra, India.

*Corresponding Author E-mail: drvinraj@gmail.com

 

ABSTRACT:

Simple sensitive and accurate extractive spectrophotometric methods have developed for the estimation of Clopidogrel bisulphate in pharmaceutical dosage form. The methods are based on the formation of coloured complexes by the drug with reagents like bromophenol blue, solochrome dark blue and bromocresol green in acidic medium. The ion associated complexes were formed and quantitatively extracted under the experimental condition in chloroform. The absorbance values were measured at 420 nm, 495 nm and 430 nm respectively. The proposed methods were validated statistically. Recoveries of methods were carried out by standard addition methods. The linearity was found to be 1-10 μg/ml, 2 -12μg/ml, 1-14 μg/ ml for methods 1, 2 and 3 respectively. The low values of standard deviation and percentage RSD indicate high precision of methods. Hence these methods are useful for routine estimation of Clopidogrel bisulphate in tablets.

 

KEYWORDS: Clopidogrel bisulphate, Bromophenol blue, Solochrome dark blue, Bromocresol green, Chloroform.

 

 

INTRODUCTION:

In this communication a new colorimetric method is developed for assay of Clopidogrel bisulphate in pharmaceutical dosage form. Clopidogrel bisulphate, chemically (+)-(S) -(2-chlorophenyl)- 6,7-dihydrothieno [3,2-c] pyridine- 5(4H)-acetic acid methyl ester sulphate is a potent oral anti-platelet agent often used in the treatment of coronary artery disease, peripheral vascular disease and cerebro vascular disease.

 

The mechanism of action of clopidogrel is irreversible blockade of the adenosine di-phosphate (ADP) receptor P2Y12 and is important in platelet aggregation, the cross-linking of platelets by fibrin.

 

 

The blockade of this receptor inhibits platelet aggregation by blocking activation of the glycoprotein IIb/ IIIa pathway. It Literature survey reveals the assay of Clopidogrel bisulfate in pharmaceutical formulations by various HPLC 1-5, spectrophotometric 6-11, TLC 12 methods for assay of clopidogrel bisulphate.

 

Simple, rapid and reliable UV spectrophotometric methods are developed for the determination of Clopidogrel bisulphate. These methods can be used for the routine analysis. In the proposed methods optimization and validation of this method are reported.

 

 

Fig. 1: Chemical Structure of Clopidogrel

 

 

 

MATERIALS AND METHODS:

A Shimadzu -160 A double beam UV-Visible recording spectrophotometer with pair of 10mmmatched quartz cell was used to measure absorbance of solutions. A Shimadzu analytical balance was used. Bromophenol blue, solochrome dark blue, bromocresol green, hydrochloric acid, potassium hydrogen phthalate and chloroform of A.R. grade were used in the study.

 

Preparation of standard solution and reagents:

Stock solution of Clopidogrel bisulphate (100μg/ml) was prepared in distilled water. From this stock solution working standard (10μg/ml) was prepared by diluting 10 ml stock solution to 100ml with distilled water. 0.6% w/v solution of bromophenol blue, 0.25% w/v solochrome dark blue and 0.2% w/v bromocresol green were prepared in distilled water respectively.

 

Potassium hydrogen phthalate buffer solution of pH 4.01 was prepared in distilled water. Dilute hydrochloric acid was used to adjust desired pH of buffer solution.

 

EXPERIMENTAL:

Method 1 (with bromophenol blue):

Into a series of separating funnels appropriate amount of the working standard drug solutions were pipetted out. To each funnel 1.0ml of buffer (pH= 4.0) and 6ml of 0.6 %w/v bromophenol blue were added. 10ml of chloroform was added to each funnel. The solutions were shaken for thorough mixing of the two phases and were allowed to stand for clear separation of the layers. The absorbance values of the chloroform layers were measured against their respective reagent blank at the wavelength of the maximum absorbance (λ max 420 nm).

 

Method 2 (with solochrome dark blue):

Into a series of separating funnels appropriate amount of the working standard drug solutions were pipetted out. To each funnel 4.0ml of buffer (pH = 1.20) and 4ml of 0.25% w/v solochrome dark blue were added. 10ml of chloroform was added to each funnel. The solutions were shaken for thorough mixing of the two phases and were allowed to stand for clear separation of the layers. The absorbance values of the chloroform layers were measured against their respective reagent blank at the wavelength of the maximum absorbance (λ max=495 nm).

 

Method 3 (with bromocresol green):

Into a series of separating funnels appropriate amount of the working standard drug solutions were pipetted out. To each funnel 1.0ml of buffer (pH= 3.8) and 5.0ml of 0.02% w/v bromocresol green were added. 10ml of chloroform was added to each funnel. The solutions were shaken for thorough mixing of the two phases and were allowed to stand for clear separation of the layers. The absorbance values of the chloroform layers were measured against their respective reagent blank at the wavelength of the maximum absorbance (λ max =430 nm).

 

Estimation from tablets:

Twenty tablets were weighed accurately and average weight of each tablet was determined. Powder equivalent to 10mg of Clopidogrel bisulphate was weighed and transferred in 100ml of volumetric flask. A 30ml of distilled water was added and sonicated for 15 minutes and filtered. The filtrate and washing were diluted up to the mark with distilled water to give concentration as 100μg/ml. Such solution was used for analysis.

 

Table 1: Values of results of optical and regression of drug

Parameter

Bromophenol blue

Solochrome dark blue

Bromocresol green

Detection Wavelength (nm)

420

495

430

Beer Law Limits (µg/ml)

01-Oct

02-Dec

Jan-14

Correlation coefficient (r2)

0.9999

0.9996

0.9998

Regression equation (y=b+ac)

Slope (a)

0.0601

0.0154

0.0251

Intercept (b)

0.0011

-0.0003

0.0014

 

RESULTS:

The extractive spectrophotometric methods are popular due to their sensitivity in assay of the drug and hence ion pair extractive spectrophotometric methods have gain considerable attention for quantitative determination of many pharmaceutical preparations. These proposed methods are extractive spectrophotometric methods for the determination of Clopidogrel bisulphate by using chloroform as solvent from its formulations i.e. tablets. The colour ion pair complexes formed is very stable. The working conditions of these methods were established by varying one parameter at time and keeping the other parameters fixed by observing the effect produced on the absorbance of the colour species. The various parameters involved for maximum colour development for these methods were optimized. The proposed methods were validated statistically and by recovery studies. The molar absorptivity show the sensitivity of methods while the precision was confirmed by %RSD (relative standard deviation). The optical characteristics such as absorption maxima (nm), molar absorptivity (l -mole-1 cm-1), co-relation coefficient (r) were calculated and are also summarized. Assay results of recovery studies are given in table 2 (A, B, C).

Table No. 2: A (Bromophenol blue)

Amount of Sample Added in (µg/ml)

Amount of Standard Added in (µg/ml)

Total amount recovered

Percentage recovery (%)

Standard deviation

Percentage of relative standard deviation (C.O.V.)

1

0

1.001925

100.1925

0.001127

0.112485

2

1

2.003091

100.1546

0.002066

0.103135

3

2

3.004918

100.1639

0.002677

0.089089

4

3

4.003888

100.0972

0.002352

0.058752

 

Mean= 0.002056

Mean= 0.090865

 

Table No 2: C (Bromocresol Green)

Amount of Sample Added in (µg/ml)

Amount of Standard Added in (µg/ml)

Total amount recovered

Percentage recovery (%)

Standard deviation

Percentage of relative standard deviation (C.O.V.)

2

0

2.006551

100.3275

0.003891

0.193905

2

2

4.006969

100.1742

0.003838

0.095784

2

4

6.010035

100.1672

0.004566

0.075975

2

6

8.014495

100.1812

0.004859

0.060633

 

Mean= 0.004289

Mean= 0.106574

Results are in good in agreement with labelled value.

 

DISCUSSION:

The percent recovery obtained indicates noninterference from the common excipients used in the formulation. The reproducibility, repeatability and accuracy of these methods were found to be good, which is evidenced by low standard deviation. The proposed methods are simple, sensitive, accurate, precise and reproducible. They are directly applied to drug to form chromogen. Hence they can be successfully applied for the routine estimation of Clopidogrel bisulphate, in bulk and pharmaceutical dosage form even at very low concentration and determination of stability of drug in formulation such as tablets. The strong recommendation is made here for the proposed methods for determination of Clopidogrel bisulphate from its formulation.

 

ACKNOWLEDGMENT:

Authors express sincere thanks to the Principal, of D. G. Ruparel college.

 

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Received on 02.11.2025      Revised on 17.11.2025

Accepted on 01.12.2025      Published on 31.01.2026

Available online from February 07, 2026

Asian J. Research Chem.2026; 19(1):6-8.

DOI: 10.52711/0974-4150.2026.00002

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