Extractive Visible Spectrophotometric Assay for Sumatriptan Succinate Estimation Based on Ion-Association Complex Formation

 

Buridi Kalyana Ramu* and K. Raghubabu

Department of Engineering Chemistry, AU College of Engineering, Andhra University Visakhapatnam-530003, AP (India)

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

 

ABSTRACT:

Two simple and sensitive extractive visible spectrophotometric methods (A and B) for the assay of sumatriptan succinate in pure and dosage forms based on the formation of colored chloroform soluble ion - association associates under specified experimental conditions are described. Two dyes namely acidic dye Naphthalene blue 12 BR (NB12BR, method A) and basic dye methylene blue (MB, method B) are utilized. The extracts of the ion-associates exhibit absorption maxima at 620nm and 650nm for methods A and B respectively. Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges (4.0 -12) µg/ml for method A, (4.0-20) µg/ml for method B respectively. The proposed methods are applied to commercial available tablets and the results are statistically compared with those obtained by the UV reference method and validated by recovery studies. The results are found satisfactory and reproducible. These methods are applied successfully for the estimation of the sumatriptan succinate in the presence of other ingredients that are usually present in dosage forms. These methods offer the advantages of rapidity, simplicity and sensitivity and low cost and can be easily applied to resource-poor settings without the need for expensive instrumentation and reagents.

 

KEYWORDS: Anti-migraine, Ion-Association method, MB, NB12BR, Statistical analysis, Tablets.

 

 


1. INTRODUCTION:

The Sumatriptan succinate (SUM) (Fig.1) is the most frequently prescribed anti- migraine drug of triptan class. It is chemically known as 3-[2-(Dimethylamino) ethyl] –N-methyl-1H indole -5- methane sulphonamide succinate (1:1) base 1. SUM is a specific and selective 5- hydroxyl tryptamine receptor (5-HT1D) agonist with no effect on the other 5HT receptor (5HT2-5 HT7) sub types. It is used widely for prophylaxis and acute relief of migraine attack with or without aura. SUM undergoes an extensive biotransformation mainly through Mono amino oxidase-A. The drug is official in EP2 and USP3 and suggests chromatographic methods for determination of SUM in bulk and tablet formulations.

 

Several analytical techniques like HPLC 4-10, HPLC-MS-MS 11-14, HPLC- ECD 15-16, HPLC-coulometry 17, capillary LC-MS-MS 18, HPTLC 19,  spectrophotometric with HPTLC20, RP-HPLC with colorimetric21, UV22, voltametry23,  capillary electrophoresis24, and  densitometry with spectrophotometric  detection25 have been reported in the literature. The main purpose of the present study was to establish a relatively simple, sensitive, validated and inexpensive visible spectrophotometric methods for the determination of SUM in pure form and in pharmaceutical dosage forms, since most of the previous methods involve sophisticated equipments which are costly and pose problems of maintenance. So the authors have made some attempts in this direction and succeeded in developing two methods based on the reaction between the drug and dyes namely NB12BR or MB under specified experimental conditions. These methods can be extended for the routine quality control analysis of pharmaceutical products containing SUM.

 

Fig.1: Chemical structure of SUM

As the extraction spectrophotometric procedures are popular for their sensitivity and selectivity in the assay of drugs, the extractive spectrophotometric technique 26 was therefore, utilized in the present work for the estimation of SUM. The present paper describes two simple and sensitive extraction visible spectrophotometric methods for the determination of SUM, based on its tendency to form chloroform extractable ion-associates with acidic dye NB12BR (CI No.20500) belonging to azo category dye (method A) or basic dye belonging to Thiazine category dye methylene blue (CI No.52015) (method B) under experimental conditions by exploiting the basic nature (tertiary nitrogen) and acidic nature (sulfonamide group) of the drug molecule.

 

2. MATERIALS AND METHODS (experimental)

Apparatus and chemicals

A Systronics UV/Visible spectrophotometer model-2203 with 10mm matched quartz cells was used for all spectral measurements. Systronics model-362 pH meter was used for all the pH measurements. A pure drug sample of SUM was provided as a gift sample by Orchid health care Ltd., India. Suminat tablets purchased from local market. All the chemicals used were of analytical grade. Aqueous solution of NB12BR (BDH,0.2%, 3.14x10-3M prepared by dissolving 200mg of NB12BR in 100ml distilled water and subsequently washed with chloroform to remove chloroform soluble impurities), pH 1.5 buffer solution( prepared mixing 289ml of 0.1M glycine solution with 711ml of 0.1M HCl and the pH of the solution was adjusted to 1.5)  Methylene blue (Fluka, 0.01%, 3.12x10-4M prepared by dissolving 10mg of methylene blue in 100ml distilled water and subsequently washed with chloroform to remove chloroform soluble impurities), pH 9.8 buffer solution (prepared by mixing 7g of ammonium chloride with 6.8 ml of liquor ammonia and diluted to 100ml with distilled water and pH was adjusted to 9.8) were prepared for methods A and B.

 

Preparation of Standard stock solution:

Method A: The standard stock solution (1mg/ml) of SUM was prepared by dissolving 100mg of SUM initially in 10ml of 0.1M sodium hydroxide and followed by dilution to 100 ml with distilled water. The working standard solution of SUM (100µg/ml) was obtained by appropriately diluting the standard stock solution with the same solvent.

 

Method B: The standard stock solution (1mg/ml) of SUM was prepared by dissolving 100mg of SUM initially in 10ml of 0.1M hydrochloric acid and followed by dilution to 100 ml with distilled water. The working standard solution of SUM (200µg/ml) was obtained by appropriately diluting the standard stock solution with the same solvent.

 

Sample solution:   About 10 tablets were pulverized and the powder equivalent to 100mg of SUM was weighed, dispersed in 25ml of IPA, sonicated for 30 minutes and filtered through Whatman filter paper No 41.The filtrate was evaporated to dryness and the residue was dissolved as under standard solution preparations.

Assay:  Aliquots of the standard SUM solution [1.0-3.0ml, 100µg/ml (method A) and 0.5-2.5ml, 200µg/ml (method B)] were placed in a series 125ml separating funnels. Then 5.0ml of pH 1.5 buffer and 2.0ml of NB12BR solution 3.17x10-3M(for method A) or  1.0 ml of pH 9.8 buffer solution and 0.5 ml of methylene blue solution (3.12x10-4M)(for method B) were added. The total volume of aqueous phase in each separating funnel was adjusted to 15.0ml with distilled water. Then 10.0ml of chloroform was added to each separating funnel and the contents were shaken for 2 minutes. The two phases were allowed to separate. The absorbances of the separated chloroform layer were measured at 620nm (method A) or 650 nm (method B) (Fig. 2 and 3 showing absorption spectra) against a reagent blank within the stability period (5 minutes to 1hour). The amount of drug was computed from its calibration graph.

 

Fig.2:  Showing Absorption spectra of SUM – NB12BR

 

Fig.3: Showing Absorption spectra of SUM-MB

 

3. RESULTS AND DISCUSSIONS:

Optimum operating conditions used in the procedure were established by adopting variation of one variable at a time (OVAT) method.  The effect of various parameters such as time, volume and strength of NB12BR, methylene blue reagents and pH buffer solutions and solvent for final dilution of the colored species were studied. The water immiscible solvents tested for the extraction of colored complex into organic phase include chloro benzene, dichloromethane, carbon tetra chloride, benzene, n-butanol or chloroform. Chloroform was preferred for its selective extraction of colored drug -dye complex into organic layer from the aqueous phase. The stoichiometric ratio of the dye-drug was determined by the slope ratio method and was found to be 1:2 and 1:1 for methods A and B respectively. The optical characteristics such as Beer’s law limit, Sandell‘s sensitivity, molar absorptivity, percent relative standard deviation, (calculated from the six measurements containing 3/4th of the amount of the upper Beer’s law limits), Regression characteristics like standard deviation of slope (Sb), standard deviation of intercept (Sa), standard error of estimation (Se) and % range of error (0.05 and 0.01 confidence limits) were calculated and the results are summarized in Table-1.  Commercial formulations containing SUM were successfully analyzed by the proposed methods. The values obtained by the proposed and reference methods for formulations were compared statistically by the t-and f-test and found not to differ significantly. As an additional demonstration of accuracy, recovery experiments were performed by adding a fixed amount of the drug to the pre analyzed formulations at three different concentration levels (50%, 75% and 100%). These results are summarized in Table-2.

 

Table - 1 Optical characteristics, precision and accuracy of the proposed methods

Parameters

Method A

Method B

גmax(nm)

620

650

Beer’s law limit(µg/ml)

4- 12

4-20

Sandell’s sensitivity(µg/cm2/0.001 abs. unit

0.020703934

0.036144578

Molar absorptivity (Litre/mole/cm)

19972.05

11440.1667

Regression equation

(Y)= a +b x

 

 

 

Intercept (a)

-0.122

0.001

Slope(b)

0.060

0.027

%RSD

0.640

0.866

% Range of errors(95% Confidence  limits)

0.05 significance level

0.01 significance level

 

 

0.672

 

 

0.909

1.0538

1.426

 

Chemistry of colored species:  In method A the protenated nitrogen (positive charge) of the drug molecule in acid medium is expected to attract the oppositely charged part (negative charge) of the dye and behave as a single unit being held together by electrostatic attraction. In method B the negative charged nitrogen of sulfonamide group of SUM molecule in basic medium is expected to attract the positive charged part of the basic dye methylene blue and form an ion pair held together through electrostatic attraction as given in scheme (Fig.4).

 


 

Fig.4 Scheme of the proposed methods


 

 


Table-2 Analysis of SUM in pharmaceutical formulations

Method

*Formulations

Labeled Amount (mg)

Found by Proposed Methods

Found by Reference Method  ± SD

#% Recovery by Proposed Method ± SD

**Amount found ± SD

t

F

A

Tablet-1

25

24.89±0.104

1.565

4.70

24.78±0.048

99.56±0.417

Tablet-2

50

49.69±0.089

1.157

1.97

49.65±0.125

99.38±0.178

B

Tablet-1

25

24.82 ± 0.078

1.94

2.66

24.78 ± 0.048

99.27 ±  0.314

 

Tablet-2

50

49.66  ± 0.098

0.315

1.62

49.65± 0.125

99.32 ±  0.196

* Tablet- 1 and Tablet-2 from two different companies; **Average ± Standard deviation of six determinations, the t- and f-values refer to comparison of the proposed method with UV reference method. Theoretical values at 95% confidence limits t =2.57 and F = 5.05.

# Recovery of 10mg added to the pre analyzed sample (average of three determinations).

Reference method (reported UV method) using double distilled water (גּ max=220nm).


 

4. CONCLUSION:

A significant advantage of an extraction spectrophotometric determination is that it can be applied to the determination of individual compounds in a multi component mixture. This aspect of spectrophotometric analysis is of major interest in analytical chemistry, since, it offers distinct possibilities in assay of a particular component in a complex dosage formulation. In the present study, SUM was determined successfully as pure compound as well as a component in representative dosage formulations. The proposed methods applicable for the assay of drug and the advantage of wider range under Beer’s law limits. The proposed extractive visible spectrophotometric methods are validated as per ICH guide lines and  possess reasonable precision, accuracy, simple, sensitive and can be used as alternative methods to the reported ones for the routine determination of SUM depending on the need and situation.

 

5. ACKNOWLEDGEMENTS:

One of the authors (B.Kalyana Ramu) is grateful to University Grants Commission, New Delhi, for providing financial assistance under the Teacher Fellowship (ETFAPAN081, under XI plan).  The authors are very much thankful to the m/s orchid health care for providing gift sample of the drug and convey their respectable thanks to retired Prof CSP Sastry,  School of chemistry, Andhra University, for his advice and suggestions given in this work.

 

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Received on 30.04.2011       Modified on 17.05.2011

Accepted on 31.05.2011      © RJPT All right reserved

Research J. Pharm. and Tech. 4(8): Aug. 2011; Page 1212-1215