Simultaneous Estimation of
Aspirin and Atorvastatin Calcium in Capsule Dosage Form by Spectrophotometric
Method
R.K. Nanda1*, S.E.
Potawale1, V.V. Bhagwat1, S.C.Hamane1 and R.
S. Deshmukh2
1D.Y.Patil Pratishthan’s Padmashree Dr. D. Y.
Patil Institute of Pharmaceutical, Sciences and Research, Pimpri, Pune-411018,
India.
2Sinhgad College of Pharmacy, Vadgaon,
Pune-411041, India.
*Corresponding Author E-mail: rabindrananda@rediffmail.com
ABSTRACT:
A simple, precise and economical
procedure for the simultaneous estimation of Aspirin and Atorvastatin Calcium
in capsule formulation has been developed. The first method employs
simultaneous equations (Method I) which involve absorbance measurement at 225.5
nm (λ max of Aspirin) and 246.0 (λ max of Atorvastatin Calcium).
Second method involves absorbance ratio (Method II), which uses the ratio of
absorbances measured at two selected wavelengths, one at isoabsorptive point (232.5
nm) and other being the max of one of the two compounds. Third method involves
measurement of area under curve (AUC). For this method wavelength ranges were chosen between 223.5-227.5 nm
and 244-248 nm for Aspirin and Atorvastatin Calcium
respectively. Results of analysis for methods were tested and validated for
various parameters according to ICH guidelines, hence can be adopted for the
routine analysis of Aspirin and Atorvastatin Calcium in tablet dosage form.
KEYWORDS: Aspirin, Atorvastatin Calcium,
simultaneous equation method, absorbance ratio method, area under curve method.
INTRODUCTION:
Aspirin (ASP) the well known
antithrombotic, antipyretic, analgesic agent1-2, official in USP-NF3,
BP4 and IP5. Atorvastatin Calcium (ATO) ([R-(R*,R*)]-(2-(4-fluorophenyl)-β,δ-dihydroxy-5-(1-methylethyl)-3-phenyl-4(phenyl
amino) carbonyl]-1H-pyrrole-1-heptanoic acid, calcium salt, (2:1) trihydrate),
a synthetic lipid-lowering agent is official in IP6. It is a
selective competitive inhibitor of the enzyme HMG-CoA reductase, which
catalyses the conversion of HMG-CoA to mevalonate, an important rate-limiting
step in cholesterol biosynthesis7.
Literature review reveals that
variety of methods have been reported for analysis of ASP by high-performance
liquid chromatography (HPLC)8-12, high-performance thin-layer
chromatography (HPTLC)13,14 and spectroscopy15.
Chromatographic16-22 and spectroscopic23, 24 methods have
been reported for determination of ATO, in combination with other drugs, in
bulk and pharmaceutical dosage forms.
The purpose of this study was to
develop and establish a simple, accurate, economical, and reproducible
procedure for the simultaneous HPLC analysis of Aspirin, Atorvastatin Calcium
as the bulk drug and in their combined dosage forms and validate it, in
accordance with ICH guidelines25.
EXPERIMENTAL:
Chemicals and Reagents:
Working standards of pharmaceutical grade
Aspirin, Atorvastatin Calcium were obtained from Torrent Pharmaceuticals
(Gujarat, India). Commercially available Ecosprin AV capsules [Aspirin (75mg),
Atorvastatin Calcium (10 mg)] were used. The chemicals used were of Analytical
Grade.
Instrument used:
A Shimadzu 1700 UV/Visible
spectrophotometer with 10 mm quartz cells was used.
Method I, II and III:
Standard stock solutions of 100 µg ml-1 of
Aspirin and Atorvastatin Calcium were prepared by dissolving 10 mg of each in
100 ml of methanol separately. Working standard solutions having concentrations
20 µg ml-1 each were prepared by appropriate dilutions.
They were scanned in the wavelength range
of 400-200 nm and the overlain spectra were obtained (Fig.1). Two wavelengths
225.5 nm (lmax
of Aspirin) and 246.0 nm (l max of Atorvastatin Calcium) for the formation of simultaneous
equation. For area under curve method wavelength ranges were chosen between 223.5-227.5 nm and 244-248 nm for Aspirin and Atorvastatin Calcium respectively and 246.0
nm (l max
of Atorvastatin Calcium), 232.5 nm (Isobestic point) for absorption ratio
method. The calibration curves were found to be linear in the concentration
range of 4-32 µg ml-1 for Aspirin and 4-30 µg ml-1 for Atorvastatin Calcium.
The absorptivity coefficients of each drug at above wavelengths were
determined.
Fig.1: UV overlay spectra of Aspirin and
Atorvastatin Calcium.
Simultaneous UV determination was performed
for Aspirin, Atorvastatin Calcium using commercial capsule (Ecosporin AV):
label claim: Aspirin (75 mg) Atorvastatin Calcium (10 mg), per capsule.
Ecosporin AV capsule was dissolved in 100 ml of methanol to get stock solution.
The above stock solution was further diluted to get sample solutions
concentrations of 30 and 4 µg ml-1 of Aspirin and Atorvastatin Calcium
respectively and absorbances were recorded on selected wavelengths. The
concentrations of two drugs in the mixture were calculated using equations
(Table 1).
1) Simultaneous equation method (Method
I):
Casp = A2ay1-A1ay2 / ax2ay1-ax1ay2
Cato = A1ax2-A2ax1 / ax2ay1-ax1ay2
Where, A1 and A2 are absorbance of
mixture at 225.5 nm and 246.0 nm; ax1 and ax2 absorptivities of Aspirin at
225.5 nm and 246.0 nm respectively. ay1 and ay2 are absorptivities of
Atorvastatin Calcium at 225.5 nm and 246.0 nm respectively. Casp. and Cato.
are concentrations of Aspirin and Atorvastatin Calcium.
2) Absorption ratio method (Method II):
Casp = Qm - Qy / Qx- Qy x A1
/ ax1
Cato = Qm - Qx / Qy- Qy x A1
/ ay1
Where, Qm is ratio of absorbances A1 and A2
of mixture at 246.0 nm and 232.5 nm; Qx is ratio of absorptivities ax1 and ax2
at 246.0 nm and 23.5 nm. Qy is ratio of absorptivities ay1 and ay2 at 246.0 nm
and 232.5 nm. Casp. and Cato. are concentrations of Aspirin and Atorvastatin
Calcium.
3) Area under curve method (Method III):
XATO244-248 ´ AUC 223.5-227.5 – XATO223.5-227.5 ´ AUC244-248
CASP =
XASP 223.5-227.5 ´ XATO
244-248 - XASP
244-248 ´ XATO 223.5-227.5
XASP 223.5-227.5 ´ AUC 244-248 –
XASP244-248 ´ AUC223.5-227.5
CATO =
XASP 223.5-227.5´ XATO 244-248 –
XASP 244-248 ´ XATO223.5-227.5
The stock solution was further diluted to
get sample solutions concentrations of 30 and 4 µg ml-1 of Aspirin and
Atorvastatin Calcium respectively and area under curve were recorded on
selected wavelength range(Fig.2). The concentrations of two drugs in the
mixture were calculated using equations.
Fig.2: Area under curve (AUC) spectra of
Aspirin and Atorvastatin Calcium.
Table 2: Linearity data of
Aspirin and Atorvastatin Calcium.
|
Parameters
|
Aspirin
|
Atorvastatin Calcium
|
|
Linearity range
|
4-32 µg/ ml
|
4-30 µg/ ml
|
|
r2 ± SD
|
0.998±0.28
|
0.998±0.64
|
|
Slope ± SD
|
0.044±0.038
|
0.043±0.50
|
|
Intercept ± SD
|
0.002±0.66
|
0.006±0.24
|
|
LOD (µg/ ml )
|
0.180
|
0.2475
|
|
LOQ (µg/ ml )
|
0.552
|
0.750
|
In all above methods concentration was
calculated by above mentioned formulae and percent purity was calculated. The
results obtained by proposed methods were close to the label claim of both
drugs. Linearity for Aspirin and Atorvastatin Calcium were in the range of 4-32
µg ml-1 for Aspirin and 4-30 µg ml-1 for
Atorvastatin Calcium (Table 2). The low value of standard deviation
indicates that the methods are accurate. The accuracy and reproducibility of
proposed method was checked by performing recovery studies using standard
addition method (Table 3). All the methods were found to be accurate, simple,
and rapid for simultaneous estimation of marketed formulation.
CONCLUSION:
Thus the proposed methods for
simultaneous estimation of Aspirin and Atorvastatin Calcium in capsule dosage
forms was found to be rapid, sensitive, simple, accurate and flexible. High
percentage of recovery shows that the method is free from the interference of
excipient(s) used in formulation. Therefore the method can be useful in routine
quality control of these drugs.
ACKNOWLEDGEMENTS:
The authors express their
gratitude to Dr. A. D. Deshpande, Director, Padm. Dr. D. Y. Patil Institute of
Pharmaceutical Sciences and Research, Pune, Maharashtra, India, for providing
necessary facilities. The authors are also thankful to Torrent Pharmaceuticals
Pvt. Ltd. (Gujarat) India for providing Aspirin, Atorvastatin Calcium as gift
samples.
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