1. INTRODUCTION:

Bupropion hydrochloride (BUP), (±)-2-(tert-butylamino)-3´-chloropropiophenone hydrochloride (Figure 1), is an aminoketone derivative with a pKa of 7.9 ⁽¹⁾. It is a second generation antidepressant agent with neurochemical properties different from common tricyclic antidepressants. It has been reported that Bupropion hydrochloride is a selective inhibitor of the neuronal reuptake of catecholamines (noradrenalin and dopamine) with minimal effect on the reuptake of indolamines (serotonin) and no inhibitory effect on monoamine oxidase ⁽²⁾.

Figure 1.The chemical structure of Bupropion hydrochloride

Bupropion hydrochloride in sustained release form is used in smoking cessation as the first licensed non-nicotine pharmacological therapy. Although its exact mechanism in smoking cessation is not known, it is thought to be related to reduced reuptake of dopamine in the mesolimbic system and reduced reuptake of noradrenalin in the locus coeruleus, because nicotine is known to produce activation of the mesolimbic system, resulting in dopamine release in the nucleus accumbens⁽²⁾.

Several chromatographic methods have been reported for the determination of Bupropion hydrochloride, in biological fluids including, high performance liquid chromatography (HPLC)^(1,
3-6) and liquid chromatography-tandem mass spectrometry (LC/MS/MS) ⁽⁷⁾ and in pharmaceutical preparations including HPLC⁽⁸⁾ and TLC⁽⁹⁾. Also chiral separation of Bupropion hydrochloride enantiomers on an ovomucoid column is described ⁽¹⁰⁾. Besides, using Cooper’s method, Bupropion hydrochloride stability in human plasma and pharmacokinetic profiles in different animal models were studied ^{(11, 12)}. A TLC method isalso available for the determination ofm-chlorobenzoic acid and related impurities in Bupropion hydrochloride monograph of USP XXIX ⁽¹³⁾.

The aim of this study is to develop spectrophotometric methods, which could be used for the determination of Bupropion hydrochloride in the pharmaceutical preparations. Spectrophotometry is well known and convenient method for the active drug content in the pharmaceutical analysis ^{(14, 15)}. It has superiorities regarding simplicity, low expense of operation and reduced analysis time providing the technique suitable for satisfying the increasing demand for control and routine analysis in many fields of analytical chemistry. The validation of original UV, zero, first and second order derivative UV spectrophotometric methods was investigated with respect to precision, linearity range, accuracy, limit of detection and limit of quantification obeying the suggestions of ICH guidelines ⁽¹⁶⁾.

2. EXPERIMENTAL:

2.1. MATERIALS AND METHODS:

Buproprionhcl was a gift sample by Wockhardt pharmaceutical Pvt. Ltd., India and was used without further purification. All chemicals and reagents used were of analytical grade and were purchased from Merck Chemicals, India.

2.2. INSTRUMENTATION:

For all the spectrophtometric methods, Shimadzu model 1800 double beam UV-VIS spectrophotometer with spectral bandwidth of 2 nm, wavelength accuracy of 2 nm and a pair of 1 cm matched quartz cells of 10 mm optical path length was used.

2.3. PREPARATION OF STANDARD AND SAMPLE SOLUTIONS:

Stock solution of 1000 μg/ml of Buproprionhcl was prepared in water for zero order, first order and second derivative spectrophotometric analysis. The standard solutions were prepared by dilution of the stock solution with water in a concentration range of 10,20,30,40 and 50 μg/ml with water for zero order, first order and second derivative spectrophotometric methods. Water was used as a blank solution.

2.3. ASSAY PROCEDURE:

A total of 10 tablets of Buproprionhcl were opened and the contents were weighed and mixed. Accurately weighed and powdered. An aliquot of powder equivalent to the weight of 1 tablet was accurately weighed and transferred to volumetric flask and was dissolved in 100 ml of water and made up to the volume with water. The solutions were filtered through a 0.45 μm nylon filter and sonicated for about 15 min and then volume made up with water. This solution was filtered to remove any insoluble matter. The filtrate was collected in a clean flask. Appropriate dilutions were made to obtain 50 μg/ml with water from stock solution for zero order, first order and second order derivative spectrophotometric methods.

3. RESULTS AND DISCUSSION:

The zero order, first order and second order derivative spectra for Buproprionhcl were recorded at the wavelength of 251 nm, 240 nmand 224 nm respectively.(Fig. 2,3,4)

Figure 2. Zero order derivative spectrum of 10-50 μg/ml of Buproprionhcl in water

Figure 3. First order derivative spectrum of 10-50 μg/ml of Buproprionhclhcl in water

Figure 4.Second order derivative spectrum of 10-50 μg/ml of Buproprionhcl in water

3.1. LINEARITY AND RANGE:

Under the experimental conditions described, the graph obtained for zero order, first order and second order derivative spectra showed linear relationship. Regression analysis was made for the slope, intercept and correlation coefficient values. The regression equations of calibration curves were y = 0.0364x - 0.0237 (r² = 0.9955) at 251 nm for zero order derivative spectrophotometry, y = 0.00017x - 0.001 (r² = 0.9955) at 240 nm for first order derivative spectrophotometry andy = 922.25x – 1.1304 (r² = 0.996) at 224 nm for second order derivative spectrophotometry.(Fig. 5,6,7) The range was found to be 10-50 μg/ml for zero order, first order and second order derivative spectrophotometric methods. (Table I).

Fig. 5 : Linearity Garph of Zero order derivative of Buproprionhcl

Fig. 6 : Linearity Garph of First order derivative of Buproprionhcl

Fig. 7 Linearity Garph of Second order derivative of Buproprionhcl

Table I :Stastical data for the calibration graph for determination of Buproprionhcl by proposed method

Parameters

Zero order derivative

First order

dwrivative

Second order derivative

Linearity range

10-50 μg/ml

r²± S.D.

0.9955

0.996

3.2. PRECISION:

To determine the precision of the method, Buproprionhcl solutions at a concentration of 50μg/ml were analyzed each six times for zero order, first order and second order derivative spectrophotometric methods. Solutions for the standard curves were prepared fresh everyday (Table II)

Table II: Results of Intra and Inter Day Precision

Methods	Intra Day Precision		Inter Day Precision
Methods	S.D	% RSD	S.D	% RSD
Zero derivative	0.195	0.194	0.206	0.206
First derivative	0.675	0.669	0.681	0.670
Second derivative	1.045	1.032	1.050	1.076

3.3. RECOVERY:

To study the accuracy of the proposed methods and to check the interference from excipients used in the dosage forms, recovery experiments were carried out by the standard addition method. This study was performed by addition of known amounts of Buproprionhcl to reanalyzed solutions of commercial tablets (Table III).

Table III: Data of recovery studies Zero order derivative spectrophotometric method

Actual concentration (μg/ml)	Observed concentration (μg/ml)	Recovery (%)	% RSD
8	7.99	99.92	0.206
10	10.01	100.01	0.216
12	12.03	100.03	0.218

3.4. ANALYSIS OF THE MARKETED FORMULATION:

There was no interference from the excipients commonly present in the tablets. The drug content was found to be 99.98% with a % R.S.D. of 0.213, 101.56% with a % R.S.D. of 0.670 and 99.79% with a % R.S.D. of 1.043 for zero order, first order and second derivative spectrophotometric methods respectively. It may therefore be inferred that degradation of Buproprionhcl had not occurred in the marketed formulations that were analyzed by this method. The low % R.S.D. value indicated the suitability of this method for routine analysis of Buproprionhcl in pharmaceutical dosage form (Table IV). The summary of the validation parameters is depicted in (Table V).

Table IV : Assay results for the determination of Buproprion HCl in pharmaceutical formulation

Parameters	Drug Content (%)	% RSD
Zero order derivative	99.98	0.213
First order derivative	101.56	0.670
Second order derivative	99.79	1.043

n=6, Average of three concentrations 50 μg/ml.

Table V : Summary of validation parameters

Parameter	Zero order derivative method	First order derivative method	Second order derivative method
Wavelength (nm)	251	240	224
Linearity range (μg/ml)	10-50	10-50	10-50
Correlation coefficient	0.9955	0.9955	0.996
Mean recovery %	99.98	100.78	99.79
Precision(%±RSD)
(a) repeatability	0.194	0.669	1.032
(b) Inter day	0.206	0.670	1.076

4. CONCLUSION:

Simple, fast and reliable derivative spectrophotometric methods were developed for the routine determination of Buproprionhcl. The developed methods can be concluded as accurate, sensitive and precise and can be easily applied to the pharmaceutical formulation.

5. ACKNOWLEDGEMENT:

It gives me immense pleasure to express my gratitude towards my Guide Dr. (Mrs.) M.D. Game for her continuous guidance and Vidyabharati college of Pharmacy for providing the facility for the research work.

6. REFERENCES:

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Received on 29.02.2013 Modified on 20.02.2013

Asian J. Research Chem. 6(6): June 2013; Page 573-576