Spectrophotometric Estimation of Risedronate Sodium in Bulk and Pharmaceutical Formulations using Multivariate Technique
S. Kathirvel, V. Sahiti and A. Suneetha*
Department of Pharmaceutical Analysis, Hindu College of Pharmacy, Amaravathi Road, Guntur-2, A.P, India.
*Corresponding Author E-mail: asstprofsuneetha@gmail.com
ABSTRACT:
A sensitive, accurate and economical UV spectrophotometric method with multivariate calibration technique for the determination of risedronate sodium in bulk drug and pharmaceutical formulation has been described. This technique is based on the use of the linear regression equations by using relationship between concentration and absorbance at five different wavelengths. The results were treated statistically and were found highly accurate, precise and reproducible. The method is accurate, precise and linear within the range 10-60µg/ml. There was no interference from the excipients. This statistical approach gives optimum results for the eliminating fluctuations coming from instrumental or experimental conditions.
KEYWORDS: UV Spectrophotometry; Multivariate Calibration; Pharmaceutical Formulation.
INTRODUCTION:
Risedronate sodium (sodium trihydrogen [1-hydroxy-2-(3-pyridyl) ethylidene] diphosphonate) is a pyridinyl bisphosphonate that induces remission in patients with Paget's disease. It is given in bone disorders in which excessive bone resorption is a problem, such as Paget's disease of bone and osteoporosis. The clinical utility of bisphosphonates resides in their ability to inhibit bone resorption. The mechanism by which this antiresorptive effect occurs is not completely known, but it is thought that the bisphosphonate becomes incorporated into bone matrix and is imbibed by osteoclasts during resorption1- 2. Several methods have been applied in the literature for the determination of risedronate. The techniques used in this connection include spectrophotometry3, liquid chromatography-tandem mass spectrometry4, enzyme linked immunosorbent assay5 and ion-pair high-performance liquid chromatography6-9.
Risedronate sodium
Present study involved development of a simple UV spectrophotometric method for the estimation of risedronate sodium in bulk and tablet dosage forms by using multivariate technique. Method for the determination of metformin using multivariate technique10 has been reported. The proposed method is based on the direct determination of risedronate sodium with a high degree of accuracy and sensitivity. The method is easy, least expensive and is applicable to the bulk drug and dosage formulations. This paper describes the application of UV spectral multivariate calibration technique having simple mathematical content for the quantitative determination of risedronate sodium in pharmaceutical formulation. The solubility of risedronate sodium was determined in a variety of solvents, from the solubility studies drug was found to be freely soluble in water. An absorption maximum was found to be 262 nm, when the spectrum was scanned for the drug dissolved in water.
EXPERIMENTAL:
Materials and Methods:
Reference standard of risedronate sodium was procured from Orchid Pharmaceuticals Ltd., Chennai. The tablet formulation was procured from local pharmacy. Spectroscopic analysis was carried out on a Systronics UV-Visible spectrophotometer – 117 with 1cm matched quartz cells.
Mutivariate Technique:
The basis of this method i.e. multivariate spectral calibration contains the use of linear regression functions obtained at five different wavelength set. This approach is based on the reduction of multi-linear regression functions to univariate data set, which provides more sensitive determination than the classical UV method. In case of single wavelength UV spectrophotometry, some errors may occur because of instrumental variations and other sources. Under optimized conditions the applied statistical method provides considerable resolving power, sensitivity, rapidity and low cost for the quantitative analysis, quality control and routine analysis of subject compounds. The mathematical algorithm of this approach is based on following summation of multivariate to univariate data sets.
FIGURE- 1: THE ABSORPTION SPECTRUM OF RISEDRONATE SODIUM AT 262nm
If the absorbance of an analyte (Z) is measured at five wavelengths set (λ = 258, 260, 262, 264 and 266 nm), straight line equation can be written as Aλ = a×(Cz+k).. . (1) Where Aλ represent the absorbance of the analyte, a is the slope and k is the intercept of linear regression function of the analyte. C Z represents the concentration of analyte. At five selected wavelengths, the equation system can also be summed as; A T = a× (C Z + b) × (C Z +c) × (C Z + d) × (C Z +e) × (C Z +K T). . (2) which can be simplified to A T = C Z (a+b+c+d+e) +K T. . .(3) where a, b, c, d, e are the slopes, A T and K T represents the sum of absorbance obtained and sum of intercepts of regression equations at five-wavelength set respectively. The concentration of the Z analyte in a mixture can be calculated by using the Equation C Z = A T -K T / (a+b+c+d+e). (4)
Preparation of standard solution:
Standard stock solution of risedronate sodium reference standard (100 μg/ml) in 100 ml calibrated flask was prepared with distilled water. A validation set consisting of solutions in working range of 10-60 μg/ml were freshly prepared and scanned in the UV region. The absorption maxima observed at 262 nm was recorded and plotted against concentration, which followed the Beer and Lambert's law and gave a straight line (r=0.9999). In order to improve this correlation and minimize instrumental fluctuations, absorbance of these solutions was measured over a range surrounding 262 nm. The five linear regression functions at the wavelengths of 258, 260, 262, 264 and 266 nm for reference standard was calculated using relationships between the absorbance and concentration
FIGURE- 2: CALIBRATION CURVES OF RISEDRONATE SODIUM AT DIFFERENT WAVELENGTHS.
TABLE- 1: REGRESSION CHARACTERISTICS OF PROPOSED METHOD
Wavelength (nm) |
Regression equation |
r |
LOD |
LOQ |
% RSD |
258 |
A=0.0164x+0.0085 |
0.9999 |
2.49 |
7.562 |
0.637 |
260 |
A=0.0166x+0.01 |
0.9995 |
1.299 |
3.93 |
0.517 |
262 |
A=0.0175x+0.0149 |
0.9988 |
2.42 |
7.35 |
0.580 |
264 |
A=0.0171x+0.0097 |
0.9997 |
1.866 |
2.621 |
0.408 |
266 |
A=0.0163x+0.0059 |
0.9993 |
2.26 |
6.875 |
0.501 |
r is correlation coefficient; LOD is Limit of Detection; LOQ is Limit of Quantitation; RSD is Relative Standard Deviation.
TABLE 2: CONCENTRATION OF RISEDRONATE SODIUM IN FOUND IN SAMPLE SOLUTIONS
Concentration (mcg/ml) |
wavelength |
Multi UVa
|
||||
258nm |
260nm |
262nm |
264nm |
266nm |
||
10 |
11.37 |
9.93 |
9.93 |
9.875 |
9.75 |
9.9 |
20 |
19.56 |
20.125 |
21.25 |
20.43 |
19.62 |
20.2 |
30 |
30.625 |
30.625 |
31.85 |
31.61 |
30.62 |
30.01 |
40 |
40.68 |
41.37 |
41.93 |
41.75 |
41.25 |
40.06 |
50 |
50.93 |
50.81 |
51.62 |
52.31 |
50.25 |
50.58 |
60 |
59.625 |
60.5 |
61.125 |
60.81 |
59.625 |
60.537 |
a Multivariate UV data, concentration in mcg/ml
TABLE 3: ASSAY RESULTS OF RISEDRONATE IN TABLETS
S. No. |
Drug Name |
Label Claim |
Amount found in mg * |
% Purity * |
1. |
Risofos |
35 mg |
34.98 |
99.94 |
2. |
Genfos |
35 mg |
34.99 |
99.97 |
* Means value of six determination.
TABLE 4: INTRA AND INTER DAY PRECISION OF THE DEVELOPED METHOD
Drug concentration (µg/ml) |
Intraday Concentration found* |
% R.S.D |
Inter day Concentration found* |
% R.S.D |
10 |
10.01 |
0.758 |
9.99 |
0.222 |
20 |
20.66 |
0.196 |
20.82 |
0.459 |
30 |
30.27 |
0.939 |
30.0 |
0.884 |
* Average of three determinations
TABLE 5: ACCURACY OF THE PROPOSED METHOD
Concentration of drug in formulation (µg/ml) |
Concentration of Pure drug added (µg/ml)* |
Total concentration of drug found (µg/ml)* |
%Analytical recovery* (± SD) |
10 |
24 |
33.61 |
99.73±0.041 |
10 |
30 |
40.19 |
100.47±0.035 |
10 |
36 |
46.52 |
101.13±0.050 |
* average of three determinations
Estimation of risedronate sodium in tablets:
Twenty risedronate sodium tablets were powdered in a mortar and an amount equivalent to 10 mg of drug was dissolved in 100 ml distilled water to make a solution (100 μg/ml), which was further diluted in the working range of 10-60 μg/ml. This study showed the applicability of multivariate linear regression approach to the UV data obtained at different wavelengths for the better calibration and tablet analysis. Statistically, the use of infinite number of data measured for a sample analysis makes the results closer to the real result. The unknown concentration of risedronate sodium in tablets of two different brands was determined by the Eqn. 4 using the sum of absorbance obtained at above wavelengths for samples.
Method validation:
The method was validated according to International conference on Harmonization complete reference guidelines in order to determine the linearity, sensitivity, accuracy and precision.
Accuracy of the method was determined by recovery studies. Different concentrations of pure drug (24, 30, 36 mcg/ml) were added to a known pre-analysed formulation sample and the total concentration was determined. The percent recovery of the added pure drug was calculated as follows
% Recovery= [(Cv-Cu)/Ca] ×100,
Whereas, Cv, the total drug concentration measured after standard addition, Cu, drug concentration in the formulation and Ca, drug concentration added to the formulation.
Precision of the method was done by performing Inter-day and Intraday analysis over a period of one week. LOD is the lowest concentration of an analyte that an analytical process can reliably detect; LOQ is defined as the lowest concentration of the standard that can be measured. The LOD and LOQ were calculated according to ICH guidelines as LOD=3.3σ/S and LOQ= 10σ/S where σ is the standard deviation of the lowest standard concentration and S is the slope of the standard curve.
RESULTS AND DISCUSSIONS:
The proposed method for the estimation of risedronate sodium in pharmaceutical dosage form was found to be simple, economic, accurate and more precise. The absorption spectrum of risedronate sodium in distilled water was scanned over the range of 200-350 nm, which shows an absorption maximum at 262 nm (Fig.1) and obeyed Beer’s law in the range of 10-60µg/ml with a correlation coefficient of 0.9999. The calibration curves of risedronate sodium at different wavelengths are shown in Fig-2. The regression characteristic of the proposed method for standard drug is incorporated in Table-1. The amount of risedronate present in the sample solutions were calculated by using multivariate technique. The results are shown in Table- 2 and 3. The method was validated in terms of accuracy and precision. The accuracy of the proposed method was determined by performing recovery studies in sample solution. The % recovery was found to be 99.73-101.13 indicates that the method is accurate. The results are given in Table-4. Precision of the method was checked by intra and inter day studies. The calculated % RSD for precision was found to be less than 2%. The results are presented in Table-5.
CONCLUSION:
Concept behind this effort was to minimize the uncertain hindrances caused during the observation. In this Paper, statistical analysis with multivariate spectral technique was used. The data obtained for the estimation of risedronate sodium in bulk and drug formulation evidenced the high level accuracy and precision after multivariate calibration. Percent recovery and found concentration of active ingredient in pharmaceutical formulations showed that the amount of drug present is consistent with the label claim. Hence, this method is very useful with very simple mathematical contents, is more reliable than the other spectrophotometric methods and strongly recommends the application in calibration models for a routine analysis.
ACKNOWLEDGMENT:
The authors are thankful to Orchid Pharmaceuticals, Chennai for providing the gift sample of risedronate sodium and the Management of Hindu College of Pharmacy, for providing the necessary facilities to carry out the research work.
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Received on 12.05.2010 Modified on 28.05.2010
Accepted on 13.06.2010 © RJPT All right reserved
Research J. Pharm. and Tech.3 (4): Oct.-Dec.2010; Page 1209-1212