ISSN 0973-0206
Sci. & Soc. 10(2) 147-154, 2012
Simple Spectrophotometric Determination of Buspirone Hydrochloride in Bulk Drug and Pharmaceutical Dosage Forms Jose Kurien, Thomas Kurian and Anny Mathew College of Pharmaceutical Sciences, Govt. Medical College, Kottayam, Kerala, India-686 008. Email:
[email protected] Received on 19 July 2012; Accepted on 6 August 2012
Abstract A simple and sensitive spectrophotometric method was developed for the determination of Buspirone HCl in pharmaceutiucal dosage forms. The method is based on the reaction of Buspirone with bromothymol blue. The complex was quantitatively extracted into chloroform at pH 3.4 followed by spectrophotometric determination at 408 nm. The complex was stable upto 2 days and obeyed Beer’s law over the concentration ranges of 2.5-25μg/ml. No significant interference was observed from excipients, colouring and flavouring agents commonly used in the formulation. The proposed method has been applied successfully for the determination of Buspirone in pharmaceutical dosage forms. Keywords: Spectrophotometry, Buspirone, Bromothymol blue, Ion-pair complex.
1. Introduction Buspirone is chemically 8-[4-(4-pyrimidin-2-ylpiperazin-1-yl)butyl]-8azaspiro[4,5]decane-7,9-dione hydrochloride. It is a nonsedating antianxiety agent. It has dopaminergic, adrenergic and serotonin modulating properties. The USP describes the assay of Buspirone either in pure form or in Tablets by HPLC. Several analytical methods have been reported for the determination of Buspirone in raw material, dosage forms and biological fluids. These methods include spectrophotometry,1-4 HPLC, 5,6 polarography,7,8 GC 9 and capillary zone electrophoresis.10,11 Extractive spectrophotometric procedures are popular for their sensitivity in the assay of drugs. Therefore, ion-pair extractive spectrophotometry has received considerable attention for the quantitative determination of many pharmaceutical compounds. The official HPLC methods12 for the determination of Buspirone are time consuming with laborious procedures or costly equipments for routine analysis. Therefore, development of simple, fast and accurate methods for the analysis of Buspirone in raw material and dosage forms, which can be used in quality control laboratory is a necessity. The aim of the present study was to develop and validate a simple method for determination of Buspirone using spectrophotometric method which can be used as an
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alternative to the official method or other recommended procedures in quality control laboratories.
2. Experimental 2.1 Materials and Methods a) Apparatus
Shimadzu UV-visible recording spectrophotometer (UV-240 Graphicord, Shimadzu Corporation, Japan) with 1cm quartz cells was used for the studies. The pH values of all buffers were adjusted using a Metrohm 692 pH meter. b) Chemicals and Reagents
All chemicals were of analytical reagent grade (Merck, Germany) unless otherwise specified. Double distilled water was used to prepare all solutions. Freshly prepared solutions were always used. USP standard acid phthalate buffer solution (pH 3.4) was prepared by mixing 50 ml of 0.2M potassium hydrogen phthalate solution with 10.4 ml of 0.2M hydrochloric acid solution and the solution was diluted to 200 ml with water. The pH of the solution was checked using a pH meter. Bromophenol blue reagent is prepared by dissolving 100 mg in minimum amount of water, diluted with water and filtered. The solution was made upto 100 ml with water. Buspirone HCl was obtained from Alidac Genetics and Pharmaceuticals, Ahmedabad. c) Standard Solution of the Drug
An accurately weighed amount of 50 mg of Buspirone HCl was dissolved in water and made upto 100 ml with water in standard flask. The solution has a concentration of 500 μg/ml. d) Recommended Procedure
From the Buspirone HCl stock solution 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45 and 0.50 ml portions each were pipette out using a 1.0 ml graduated pipette (1×200) into 10 separating funnels. 1ml of pH 3.4 buffer was added to each of the separating funnels, followed by 2ml of bromophenol blue reagent. The solutions were mixed and volume was adjusted to 10ml by adding appropriate quantities of water. The solutions
Figure 1. Structure of Buspirone Hydrochloride
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Figure 2. Spectral Scan of Buspirone-Bromophenol blue Complex
were extracted twice with 4ml portions of chloroform. The combined chloroform extracts were made upto 10ml with chloroform in 10ml standard flasks. The absorbance of the resulting solutions were measured at 408nm using the reagent blank. The standard calibration curve was prepared to calculate the amount of the analyte drug in unknown samples. e) Procedure for the Dosage Form
Three samples of Buspirone HCl tablets were analysed by the proposed method. i) Extraction of Buspirone HCl Tablets
20 tablets were accurately weighed and powdered in a glass mortar. A quantity of tablet powder equivalent to 50mg of Buspirone HCl was accurately weighed and transferred to a small conical flask. 40ml of water was added and swirled gently for 10 minutes. This aqueous solution was filtered into a 100ml standard flask through a whatmann filter paper. The residue was extracted again with 20ml of water and passed through the filter and the final volume was made upto 100ml with water. ii) Development of the Colour
The colour complex was developed using 2 different concentrations of the extracted Buspirone HCl solution. 0.2 and 0.3ml of the extracted solution was mixed with 1ml of the pH 3.4 buffer and 2ml of bromophenol blue solution in separating funnels. The volume was adjusted to 10ml by adding appropriate quantities of water. It was extracted Table 1. Data for Analysis of Buspirone HCl Tablets Tablet sample Label claim Proposed method Official method % Label claim Sample A 10mg 9.998 9.998 99.98 Sample B 10mg 9.997 9.997 99.97 Sample C 10mg 9.999 9.999 99.99
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Table 2. Data for the comparison of Proposed method with Official method Sl. No. 1 2 3 4 5 6
Official method Tablet Tablet Tablet A B C Buspirone HCl content per 9.998 9.997 9.999 tablet of average weight % Label claim 99.98 99.97 99.99 Standard deviation 0.070 0.073 0.060 Coefficient of variation 0.00065 0.0007 0.0006 Standard error 0.039 0.04 0.035 Limits of error 0.661 0.652 0.657 Analytical data
Proposed method Tablet Tablet Tablet A B C 9.998 9.997 9.999 99.98 0.071 0.00064 0.037 0.663
99.97 0.073 0.00069 0.041 0.648
99.99 0.061 0.00059 0.036 0.627
Table 3. Data for Beer’s Law Plot Sl. No. 1 2 3 4 5 6 7 8 9 10
Volume of Buspirone HCl soln (ml) 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
Concentration in the final soln. (μg/ml) 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 22.5 25.0
Absorbance at 408nm 0.117 0.229 0.343 0.452 0.561 0.678 0.795 0.909 1.017 1.140
with chloroform as in standard solutions. The absorbance of the chloroform extract was measured at 408nm against the reagent blank. Three different samples of Buspirone HCl tablets were analysed by this method. The results are furnished in the table 2. Using the data in the table 2 the content of Buspirone HCl per tablet was determined from the Beer’s law plot.
3. Results and Discussion a) Spectral Characteristics Absorption spectra of the yellow coloured Buspirone-bromophenol blue complex is shown in Fig.2 with a maximum absorbance (λmax) at 408nm. The complex formation was completed immediately after all reagents were added, no heating or standing time was needed. The colour complex was stable for about 48 h at room temperature (25p C).
b) Optimization of Variables and Method Development A number of preliminary experiments were performed to optimize the necessary conditions for rapid and quantitative formation of coloured ion-pair complex to achieve the maximum stability and sensitivity. Optimum conditions were fixed by varying one 150
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parameter at a time while keeping other parameter constant and observing its effect on the absorbance at 408nm.
c) Effect of pH The influence of pH of buffer solution on the development and stability of colour complex was tested using different systems as phthalate, potassium hydrogen phthalate, phosphate and acetate buffers. The acid phthalate buffer solution was the buffer of choice which did not interfere and gave the highest sensitivity for complex formation and extraction. The absorbance of Buspirone-bromothymol blue ion-pair was examined at different pH values range of 1-5. The maximum colour intensity was observed at pH ranges of 2.9-3.9 and maximum absorbance was achieved with 10ml of pH 3.4 buffer solution. This condition was applied throughout the experiment.
d) Selection of the Extracting Solvent As it was mentioned before chloroform was preferred to other solvents (carbon tetrachloride, dichloromethane and ether) because of higher stability of extracted product, almost higher efficiency on colour intensity, selective extraction of the Buspirone-bromo phenol blue complex from the aqueous phase and higher absorbance. Therefore extraction with 2×5ml of chloroform had a good recovery of the complex in a short time.
e) Analytical Data Under the optimized experimental condition, calibration curve was constructed by plotting the absorbance at λmax against the concentration of Buspirone HCl. Beer’s law range, molar absorptivity, Sandell’s sensitivity, regression equation, and correlation co-efficient were determined for the proposed method and are given in table 1. A linear relationship was found between the absorbance at λmax and the concentration of the drug in the range of 2.5-25μg/ml for Buspirone HCl in the final measured volume of 10ml with molar absorption coefficients of 1.97×107 l/mol.cm. Regression analysis of the Beer’s law plot at λmax revealed a good correlation (r 2 =0.997). The graph showed negligible intercept and were described by the regression equation, y = 0.0453 C + 0.0008; where y is the absorbance of 1cm layer, 0.0453 is the slope, 0.0008 is the intercept and C is the concentration of the measured solution in μg/ml obtained by the least squares method. The high molar absorptivity of the resulting coloured complex indicates high sensitivity of the method.
f) Sensitivity The limit of quantification that can be determined with RSD0.83%.
h) Application to Dosage Forms The proposed method was successfully applied to a determination of Buspirone HCl in commercial tablets. The applicability of the proposed method for assay of Buspirone HCl in formulations was examined by analyzing various formulations and the results are tabulated in table 2. Five replicate determinations were made. Satisfactory results were obtained and were in a good agreement with the label claims (table 4) for different batches. The results were reproducible with low RSD values (1.65%).
i) Comparison with Official Method The reliability and validity of the proposed method was established by parallel determination against HPLC method described in United States Pharmacopoeia (2008). The results were indicated in table 1. The results of analysis of the commercial formulation and the recovery study of drug suggested that commonly used additives and experiments do not interfere with the assay procedure. The proposed method is sufficiently sensitive to permit determination of low concentration of Buspirone HCl (2.5μg/ml). Different methods have been reported for determination of Buspirone HCl in pharmaceutical preparations. Nevertheless, most of these techniques utilize sophisticated instruments and reagents that are not available in many laboratories or need well trained personnel. A significant advantage of the extractive spectrophotometric technique is that it can be applied for the determination of individual compounds in a multi-component mixture. The importance of this technique lies in the chemical reactions upon which the procedure based rather than upon the sophistication of the instrument so it offers in the assay of a specific component in a complex dosage formulations. Slight variation in experimental conditions such as temperature, reagent concentration or pH do not affect significantly on this method. The reaction between Busprone and bromophenol blue takes place at only one site that was the nitrogen atom of piperazine ring attached to alkyl side chain. Unlike the standard addition method, the present method is not time consuming. It does not involve procedural steps; does not take much operator time and expertise, and there is no need for any expensive equipments and reagents unlike other methods such as HPLC. The overall advantages of the present method are its simplicity, sensitivity, rapidity and no need for expensive instruments in comparison to reported techniques. This method can be used for routine determination of Buspirone HCl in bulk drug as 152
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well as in pharmaceutical preparations.
4. Conclusion In the present study, an ion-pair formation method is described for determination of Buspirone HCl. This method is simple, rapid, accurate and applicable in different dosage forms in comparison to official method and other time consuming complicated and costly techniques such as GC and HPLC. These advantages encouraged the application of the proposed method in routine quality control laboratories for determination of Buspirone in bulk drug and pharmaceutical preparations. Acknowledgement We extend our sincere thanks to M/s Alidac Genetics and Pharmaceuticals, Ahmedabad for supplying the reference sample of Buspirone hydrochloride for the study.
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