Determination of Clopidogrel Bisulphate from Pharmaceutical Dosage Form by Extractive Ion Pair Complex Colorimetric Method

 

Rele Rajan V.*

Central Research Laboratory, D.G. Ruparel College, Mahim, Mumbai 400 016.

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

 

ABSTRACT:

Simple sensitive and accurate extractive colorimetric method is developed for the assay of clopidogrel bisulphate in pharmaceutical dosage forms. In this method drug molecule forms an ion pair complexes with thiocynate ions. The extraction of such ion pair complexes was done in chloroform with condition of experiment. The optical density of complexes were recorded at wavelength 622 nm respectively. The standard addition method was used by recovery study. The Beer’s law was applicable in the ranges 2-20 μg/ml respectively. The experimental values of percentage RSD and standard deviation showed that the method has high precision. Hence in the routine new assay method can be applied to clopidogrel bisulphate in tablets.

 

KEYWORDS: Clopidogrel bisulphate, Cobalt nitrate, Ammonium thiocynate, 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 drug in pharmaceutical formulations by various HPLC [1-5], spectrophotometric [6-11], TLC [12] methods for assay of drug.

 

Simple, rapid and reliable UV spectrophotometric assay method is suggested for the clopidogrel bisulphate. 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 10mm matched quartz cell was used to measure absorbance of solutions. A Shimadzu analytical balance was used.

Cobalt nitrate, Ammonium thiocynate, and chloroform of A.R. grade were used in the study.

 

Preparation of standard solution and reagents

Stock solution of Clopidogrel bisulphate (100 μg/ml) was prepared in distilled water. From this stock solution working standard (10 μg/ml) was prepared by diluting 10 ml stock solution to 100 ml with distilled water.

 

 

EXPERIMENTAL:

Preparation of solutions:

Stock solutions of Clopidogrel bisulphate (100μg/ml) were prepared in distilled water.

From these stock solutions, working standard solutions (10μg/ml) were prepared by diluting 10 ml stock solution to 100 μg/ ml with distilled water.

 

Preparation of reagents

The 1:2 molar proportions of cobalt nitrate and ammonium thiocynate are mixed to give reagent cobalt thiocynate in distilled water.

 

Experimental:

The different aliquots of working solution were taken in different separating funnels. In each separating funnel 1.6 ml of reagent (cobalt thiocynate) solution were added with 10 ml of chloroform. The each aliquot with reagent and chloroform were shaken for 10 minutes for thorough mixing. After the separation of the two phases, chloroform layer was taken out. The optical density values of the each chloroform layers was measured at λ max 622 nm with chloroform as reagent blank solution.

 

Estimation from Tablets:

The finely crushed powder of drug formulation (tablets) equivalent to 100 mg of was used to prepare 100 μg /ml.   A 10 μg /ml solution was prepared from above formulation solution of 100 μg /ml.  This 10 μg /ml solutions were used for assay of clopidogrel bisulphate respectively. The different aliquots of sample drug solution were used for the determination of drug contents in tablets. The concentration of the drug in the tablets was calculated using calibration curve. Fig. no.1

 

Fig. no: 2. Calibration curve

 

The standard addition method was used for recovery experiment. The values result of different parameters are reported in table no1.

 

Table 1: Values of results of different parameter of drug

Parameter

Values

Detection Wavelength (nm)

622

Optical density Limits (µg/ml)

2-20

Correlation coefficient(r2)

0.9998

Regression equation

 

Slope

0.0101

Intercept

-0.0002

 

RESULT:

The spectrophotometric methods are known for accuracy in quantitative determination of the drug with many pharmaceutical preparations. This suggested assay method is applicable determination of drug from active ingredient as well as formulation. The extractive complexes are formed are very stable. The optimizations of various parameters involved for maximum colour development were studied. The recovery study was statistically studied for the proposed methods. Assay results of recovery studies are given in table no. 2.


Table no 2: Results of recovery studies

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

2.015714

100.7857

0.009759

0.484146

2

2

4.016

100.4

0.012329

0.306993

2

4

6.018571

100.3095

0.006901

0.114656

2

6

8.024286

100.3036

0.012724

0.158571

 

 

 

 

Mean= 0.010428

Mean=0.266091

 


The noninterference from the common excipient used was observed from percent recovery obtained by calculation.

 

DISCUSSION:

The low values of standard deviations indicated good reproduction, and accuracy of such methods. The newly suggested method is simple, precise and reproducible with given range of concentration.  The method is directly used for active ingredient as well as formulation of estimation of clopidogrel bisulphate in bulk and pharmaceutical dosage form even at very low concentration in formulation such as tablets.

 

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Received on 04.10.2025      Revised on 24.12.2025

Accepted on 28.01.2026      Published on 27.05.2026

Available online from May 30, 2026

Asian J. Research Chem.2026; 19(3):182-184.

DOI: 10.52711/0974-4150.2026.00030

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