Spectrophotometric
method for the estimation of Atorvastatin calcium in pharmaceutical preparation
S. Subramanya Raj Urs*,
Gangambika H.M., Rajashekara Murthy M., Asharani D.R.
Post Graduate Department of
Chemistry, JSS College for Women, Sarawathipuram, Mysuru 570 009
ABSTRACT:
Present study describes
development and validation of UV-Spectrophotometric method for the estimation
of Atorvastatin Calcium in pharmaceutical preparation. During development of
analytical methods, methanol and hydrotropic solubilization reagent is employed
to enhance aqueous solubility of poorly water soluble Atovastatin Calcium in
dosage forms. In the proposed methods 2M Urea and 2M Thiourea solution is used
as hydrotropic solubilizing agent. Absorption maxima was determined with
10μg/ml solution by scanning in the range 200-400nm. Standard stock
solution prepared in methanol (λmax:247nm) and hydrotropic solubilization
agent in water(λmax:240nm). The proposed methods obeys Beer’s law in the
range 5-40 μg/ml. The methods were validated in terms of Linearity,
Precision and Accuracy. Results of analysis were validated statistically and by
recovery studies. It was observed that there is no interference of impurities
or excipients during the estimation of drug. This shows the adoptability of the
methods for routine analysis of drugs in marketed formulations in quality
control laboratories.
KEYWORDS:
INTRODUCTION:
Atorvastatin
is a member of the medication class known as statins, which are used primarily
as a lipid-lowering agent and for prevention of events associated with
cardiovascular disease. Atorvastatin calcium is a member of the drug class
known as statins, used for lowering blood cholesterol chemically, it is (3R,
5R)-7-(2-(4-fluropenyl) -3-phenyl-4- (phenylcarbamoy1)-5-propan- 2ylpyrrol
-1-yl)-3, 5-dihydroxyheptanoicacid, it works by inhibiting 3-hydroxy 3-methyl glutaryl co-enzyme (HMG-CoA) reductase,
an enzyme found in liver tissue that plays a key role in production of
cholesterol in the body.
The primary use of
atorvastatin are for the treatment of dyslipidemia and the prevention of
cardiovascular disease. It is recommended to be used only after other measures
such as diet, exercise and weight reduction have no time proved cholesterol
levels. It is used in hyper cholesterolemia to reduce total cholesterol, low
density lipoprotein-c. Apolipoprotein-B and triglycerides levels.
A survey of literature
revealed that analytical methods like HPLC, HPTLC are reported for
determination of Atorvastatin calcium individually and with other drug
combination. Few HPLC, Mass spectroscopy, HPTLC Methods were reported for
determination of atorvastatin calcium. Several studies have been reported for
the determination of Atorvastatin in pharmaceutical and biological fluids
including spectrophotometric methods (1,2), electrophoresis (3,4),
polarographic methods (5) and chromatographic methods with different detectors
(6,7). There are many reported methods for the determination of Atorvastatin
alone (8,9), in combination with other drugs in pharmaceutical dosage forms
(10,11) ,different LC Methods(12, 13), spectrophotometric methods(14-16),
capillary electrophoresis (17), HPTLC (18) have been reported for the
estimation of the Atorvastatin in their mixture.
Detailed survey of literature
for Atorvastatin revealed several methods based on different techniques (19,
20) like HPLC and LC-MS for its determination in plasma serum and human serum
and pharmaceutical formulation. The reported HPLC method involves costly
sophisticated instrumentation and time consuming process while HPTLC method has
no reproducibility. In the analysis of atorvastatin, major problem is
solubilisation of Atorvastatin in most of solvents during analysis.
Quantitative estimation of poorly water soluble drugs involves use of organic
solvents. Major drawbacks of organic solvents include hige cost volatility and
toxicity. Syed Najmul Hejaz Azmi et al (21) have reported HPLC –UV method for
the determination of atorvastatin and pooja A chawla et al (22) have reported a
review on various analytical methods for the analysis of atorvastatin.
Literature survey revealed
that no simple UV method has been reported to the best of our knowledge. so
emphasis was given to develop simple, sensitive, selective, precise and
accurate UV method for determination of atorvastatin calcium, therefore in the
proposed methods 2M urea and 2M thiourea solution is used as hydrotropic
solubilizing agent to enhance the aqueous solubilities of atorvastatin calcium
in dosage forms.
MATERIALS AND METHODS:
A double beam UV-Visible
Spectrophotometer was used. Absorption spectra of both test and standard
solutions were recorded over the wavelength range of 200-400nm using 1cm quartz
cell. Atorvastatin calcium was supplied as gift sample, all other
chemicals and reagents used were of analytical grade.
Preparation of standard stock
solution:
Method: 1
Accurately weighed 25mg of
Atorvastatin standard powder was transfered in to 25ml volumetric flasks.
dissolved in methanol and volumes were made up to the mark with same solvent,
from the above solutions of Atorvastatin 10ml aliquots were pipetted and
transferred in to 100ml volumetric flasks diluted up to the mark with methanol
to obtained final solutions of 100µg/ml.
Method: 2 and 3
For hydrotropic solubilization
20mg of pure atorvastatin calcium was dissolved in 50ml of 2.0M urea/ thiourea
solution and stirred for 15 minutes and the final volume of both solutions was
made up to 100ml with distilled water, the solution was filtered through
whatmann filter paper No 41, this solution was further diluted with distilled
water to prepare working concentrations of 100mg/ml of atorvastatin calcium.
Detection of absorption
maxima:
For the selection of
analytical wavelength, standard stock solution of atorvastatin calcium prepared
was scanned in the (range of 200 to 400nm in 1cm cell) against suitable solvent
as blank. The UV spectrum obtained exhibits absorption maxima (λmax)
at 246nm (method 1) 240nm (method 2 and 3)
Preparation of sample solution:
Method:1
Twenty tablets were accurately
weighed, their mean weight was determined and were ground to fine powder in a
glass mortar. An amount of powdered mass equivalent to 25mg of atorvastatin
weighed and transferred in to conical flask. The drugs from powder were
dissolved and extracted with methanol. To ensure complete extraction of drug it
was sonicated for 30min. the extract was filtered through whatmann filter paper
No 41, and residue was washed with methanol. The extract and washing were
pooled and transferred. To a 25ml volumetric flask and diluted with methanol.
The obtained solution of atorvastatin was further diluted in 25ml volumetric
flask to achieve final concentration of (30µg/ml).
Method :2 and 3
Tablet powder equivalent to
30mg atorvastatin calcium was weighed and transferred to a 100ml volumetric flask
70 ml of 2.0M urea(or 2.0M thiourea) solution was added to the flask and
stirred for 15 min to dissolve the drug and the final volume was made up to
100ml with distilled water. The solution was filtered through whatmann filter
paper No.41. The filtrate was diluted suitably with distilled water to get 10
µg/ml of atorvastatin calcium.
RESULTS AND DISCUSSION:
The wavelength of absorption
maxima were determined for drug Atorvastatin calcium showed maximum absorbance
at 246nm (method 1), 240nm (method 2 and 3)
Calibration Plot of Absoprtion
Maxima
Calibration curve:
METHOD 1
Standard calibration curve for
atorvastatin, covering the range 5-35 µg/ml, prepared by serial dilution with
methanol for pure drug and tablet formulation were developed and validated. The
procedure was adopted as per desired protocol. The calibration was obtained by
plotting absorbance V/s Analyte concentration. The slope and intercept of the
calibration line was determined by linear regression. The optical
characteristics (table 1) and data related to SD and RSD are given in table 2.
Table: 1
|
S. NO |
Optical characteristics |
Method.1. |
|
1 |
Absorption maxima(nm) |
247 |
|
2 |
Linearity range (µg/ml) |
5-35 |
|
3 |
Standard regression equation |
Y=0.039x+0.015 |
|
4 |
Correlation coefficient(r2) |
r2 = 0.998 |
|
5 |
Accuracy (% recovery) |
99.71 to 99.92 |
|
6 |
Precision |
|
|
7 |
LOD and LOQ |
0.998,3.025 |
Table: 2
|
Atorvastatin calcium (µg/ml) |
Intra-assay precision |
Intra –assay precision |
||
|
Mean ± S.D |
% RSD |
Mean ± S.D |
% RSD |
|
|
10 |
99.73 ± 0.3215 |
0.32 |
99.81 ± 0.2762 |
0.28 |
|
15 |
99.37 ± 0.3215 |
0.32 |
100.33 ± 0.9802 |
0.98 |
|
25 |
99.57 ± 0.6486 |
0.65 |
99.28 ± 0.9302 |
0.94 |
METHOD.2.
Quantitative estimation of
poorly water-soluble drugs involves use of organic solvents. Major drawbacks of
organic solvents include high cost, volatility and toxicity. In the present
investigation, hydrotropic solubilization is employed to enhance the aqueous
solubilities of poorly water- soluble atorvastatin calcium in tablet dosage
forms. The results of solubility studies indicated that enhancement in aqueous
solubility of atorvastatinn calcium in 2.0 M urea solution and was more than
6-7 folds as compared to their solubilities in distilled water. Therefore, this
solution was employed to extract atorvastatin calcium from the fine powder of
tablet formulation and thus analysis will become easier one. The optical
characteristic are given in the table 3
Table: 3 OPTICAL
CHARACTERISTICS
|
Optical characteristics |
Method 2 |
|
Beer’s law limit (µg/ml) |
5 -45 |
|
Regression equation |
Abs =A+B* Conc. |
|
Slope (B) |
0.0317 |
|
Intercept (A) |
0.0998 |
|
Correlation coefficient |
0.9999 |
METHOD .3.
To enhance the solubility of
atorvastatin in water 2.0 M thiourea is employed. Under the experimental
conditions described, calibration curve, precision and recovery studies were
performed. The drugs obey beer’s law in the concentration range 5-45µg/ml for
atorvastatin for all the methods with good correlation co-efficient 0.994 and
0.996 respectively. The results of commercial formulation analysis are
presented. The accuracy and reproducibility is evident from the data as results
are close to 100% and low standard deviation. Optical characteristics are given
in table 4 and analyzing of pharmaceutical formulation are given in table 5 and
6.
Table: 4 OPTICAL
CHARACTERISTICS
|
Optical characteristics |
Method 3 |
|
Beer’s law limit (µg/ml) |
5 -50 |
|
Regression equation |
Abs =A+B* Conc. |
|
Slope (B) |
0.0312 |
|
Intercept (A) |
0.0994 |
|
Correlation coefficient |
0.9994 |
Table: 5
|
Atorvastatin calcium (µg/ml) |
Intra-assay precision |
Intra –assay precision |
||
|
Mean ± S.D |
% RSD |
Mean ± S.D |
% RSD |
|
|
10 |
99.73 ± 0.3215 |
0.32 |
99.81 ± 0.2762 |
0.28 |
|
15 |
99.37 ± 0.3215 |
0.32 |
100.33 ± 0.9802 |
0.98 |
|
25 |
99.57 ± 0.6486 |
0.65 |
99.28 ± 0.9302 |
0.94 |
Table :6 Analysis of
pharmaceutical formulations
|
Methods |
Labeled amount (mg) |
Amount recovered (mg) |
% drug recovered |
Mean |
Standard deviation |
% RSD |
|
Method.1 |
10 |
9.782 |
97.82 |
9.794 |
0.1065 |
1.087 |
|
Method.2 |
10 |
9.694 |
96.94 |
|||
|
Method.3 |
10 |
9.906 |
99.06 |
The proposed
spectrophotometric method is found to be accurate, precise, economic and rapid
for estimation of atorvastatin calcium. It satisfactorily eliminates
interference from excipients. Hence it can be employed for routine analysis of
drugs in marketed formulations in quality control laboratories. The most
striking feature of this method is its simplicity, economy rapidity and
non-requiring consuming sample preparations such as extraction of solvents,
heating, degassing which are needed for HPLC procedure. It could be concluded
that the proposed procedures are simple, do not require sophisticated
techniques or instruments.
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Received on 06.02.2020 Modified on 07.03.2020
Accepted on 29.03.2020
©Asian Pharma Press All Right Reserved
Asian J. Pharm. Ana. 2020; 10(2):77-80.
DOI: 10.5958/2231-5675.2020.00013.7