J. Chil. Chem. Soc, 55, N° 1 (2010), pág: 94-96

 

A VALIDATED DENSITOMETRIC METHOD FOR ANALYSIS OF TELMISARTAN AND ATORVASTATIN CALCIUM IN FIXED DOSE COMBINATION

 

U. P. PATIL, S. V. GANDHI* M. R. SENGAR, V. S. RAJMANE

Department of Pharmaceutical Analysis, AISSMS College of Pharmacy, Kennedy Road, Pune - 411 001, MH, India
Santosh V. Gandhi
AISSMS College of Pharmacy Kennedy road, Near R.T.O., Pune. 411 001. Maharashtra, India.

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ABSTRACT

A simple, specific, accurate and precise high-performance thin-layer chromatographic method for analysis of Telmisartan and Atorvastatin calcium in fixed dose combination has been developed. The method uses aluminium plates coated with silica gel 60 F254 as stationary phase and toluene: methanol (7: 3, v/v) as mobile phase. Densitometric evaluation of the separated bands was performed at 280 nm. The two drugs were satisfactorily presolved with Rf values 0.50 ± 0.01 and 0.29 ± 0.00 for Telmisartan and Atorvastatin calcium, respectively. The respective cahbration plots were found to be linear over the range 200-1000 and 200-700 ng/band for Telmisartan and Atorvastatin calcium, respectively. This method has been successfully validated and applied for the analysis of drugs in pharmaceutical formulation.

Keywords: High-performance thin-layer chromatography, telmisartan, atorvastatin calcium

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INTRODUCTION

Atorvastatin calcium (ATV), (ßR,dR)-2-(4-fluorophenyl)-ß,d-dihydroxy-5-(1-methylethyl)-3-phenyl-4-[(phenylamino)carbonyl]-1H-pyrrole-1-heptanoic acid, calcium salt, is a synthetic cholesterol-1owering agent¹ and is official mlndianPharmacopoeia. Official assay method is by HPLC². Literature surveyreveals spectroscopic method for determination of ATV in combination with amlodipine besylate³. HPTLC methods have been reported for estimation of ATV in biological sample as a single drug⁴ and in pharmaceutical sample in combination with ezetimibe⁵. Several HPLC methods are reported for determination of ATV in bulk drugs and tablets^6-7. Stability indicating HPLC methods are also reported for estimation of ATV in combination with other drugs^8-10.

Telmisartan (TEL) is described chemically as 4[(1, 4-dimethyl-2-ßRopyl (2, 6-bi-1H-benzimidazol]-1-yl) methyl] [1, l-biphenyl]-2-carboxylic acid¹¹. TEL is useful in the treatment of mild to moderate hypertension¹². Few spectrophotometric methods have been reported for estimation of TEL in pharmaceutical dosage form as a single drug or in combination with other drugs^12-13. HPTLC methods are also reported for the determination of TEL in formulation^14-15.

Extensive literature survey reveals that no HPTLC method is available for determination of Atorvastatin Calcium and Telmisartan in combined tablet dosage form. Aim ofpresent work was to develop a simple,precise, accurate and economical HPTLC method for determination of binary drug formulation.

EXPERIMENTAL

Reagents and Chemicals

Methanol, toluene (all AR grade) were obtained from Thomas Baker (chemicals) Pvt. Ltd. (Mumbai, India). Standard bulk drug samples of TEL (99.65 % pure) and ATV (99.83 % pure) wereprovided as gift sample by Glenmark Pharmaceuticals Ltd. (Nasik, India) and Hetero Drugs Ltd. (HP, India),respectively. The pharmaceutical dosage form used in this study was Tele Act ST 20 film coated tablets (Hetero Drugs Ltd. HP, India) labeled to contain telmisartan 20 mg and atorvastatin calcium IP equivalentto atorvastatin 10 mg per tablet.

Instrumentation and Chromatographic Conditions

Chromatography was performed on 20 cm X 10 cm aluminum platesprecoated with silica gel 60 F₂₅₄ (E. Merck, Darmstadt, Germany). Before use the plates wereprewashed with methanol and activated at 110 °C for 5 min. Samples were applied to the plates as bands 6 mm wide and 6.8 mm apart by means of a Camag (Switzerland) Linomat 5 sample applicator equipped with a 100 uL syringe (Hamilton, Bonaduz, Switzerland). Linear ascending development was performed in a 20 cm X 10 cm twin trough glass chamber (Camag) using toluene: methanol (7: 3, v/v) as mobile phase after saturation

of the chamber with mobile phase vapor for 30 min. The development distance was 9 cm and the development time aproxiimately 30 min. After chromatography the plates were dried in a current of air by use of a hair dryer Densitometric scanning was performed with a Camag TLC Scanner 3 at 280 nm for all measurements. The scanner was operated by Wincats software Versión 1.4.2. The source of radiation was a deuterium lamp emitting a continuous UV spectrum between 200 and 400 nm. The slit dimensions were 5 mm X 0.45 mm and the scanning speed was 20 mm/s.

Preparation of Standard Stock Solutions

A standard stock solution of TEL and ATV wereprepared by dissolving 10 mg drug in 10 mL methanol to furnish a concentration of 1 mg/mL. From this stock solution 1 mL was further diluted to 10 mL with methanol to get working standard solution of 100 µg/mL of each drug.

VALIDATION

Theproposed method was optimized and validated in accordance with International Conference on Harmonization (ICH) guidelines¹⁶.

Linearity

The working standard solutions of TEL (100 µg/mL ) and ATV (100 µg/ mL) were applied by overspotting on a TLC plate, in the range 2-10 uL, by use of the Linomat 5 sample applicator and 100 µL syringe. The plate was developed and scanned under the conditions described above. Each amount was analyzed five times and peak areas wereprecorded. Cahbration plots of peak area againstrespective amount were established separately for TEL and ATV.

LOD and LOQ

LOD and LOQ were calculated, in accordance with ICH guidelines, as 3.3 σ/S and 10 σ/S, respectively, where o is the standard deviation of theresponse (y-intercept) and S is the slope of the cahbration plot.

Precisión

To study intra-day variation, solutions of TEL and ATV wereprepared and applied to the TLC plates in linearity range (3 concentrations x 3replicates). All the solutions were analyzed on the same day toprecord any intra day variation in thepresults. To study inter-day variation, analysis of three standard solutions in triplícate in linearity range was performed on different days.

Robustness

The effect of small, deliberate variation of the analytical conditions on the peak areas of the drugs was examined. Time from application to development (0, 10, 20, 30 min), from development to scanning (0, 30, 60, 90 min), volume of mobile phase (±10 %) and development distance (±10 %) were varied. One factor at a time was changed to study the effect.

Accuracy

To check the accuracy of the method,precovery studies were carried out by addition of standard drug solution topre-analyzed sample solution at three different levels 80, 100, and 120 % topre-analyzed sample solution. Three replicates were analyzed for each level.

RESULTS AND DISCUSSION

Selection of Detection Wavelength

After chromatographic development, bands were scanned over the range 200—400 nm (spectram sean speed 100 nm/s) and the spectra were overlain. At 280 nm, TEL as well as ATV has considerable absorbance so this wavelength was selected as detection wavelength (Fig. 1).

Method Development

Different mobile phases containing toluene, methanol, chloroform, ethyl acétate, and triethylamine in differentproportions were examined (results not shown). Toluene: methanol (7:3, v/v) was finally selected because itpresulted in acceptablepresolution of the bands with Rf values of 0.50 ± 0.01 for TEL and 0.29 ± 0.00 for ATV. The densitogram obtained from an overspotting solution of TEL and ATV is shown in Fig. 2.

Analysis of Tablet Formulation

Twenty tablets were weighed accurately and finely powdered. A quantity of powder equivalent to 10 mg ATV was weighed and transferred to a 10 mL volumetric flask containing aproxiimately 5 mL methanol. The mixture was ultrasonicated for 5 min and diluted to volume with methanol. The solution was filtered using Whatman no. 41 paper. From stock solution 1 mL was taken and diluted to 10 mL with methanol. 3 µL of this stock solution was applied to a TLC plate. After chromatographic development the peak areas of the bands were measured at 280 nm and the amount of each drag in sample was determined from therespective calibration plots. The analyticalprocedure wasprepeated six times for the homogenous powdered sample. Thepresults of commercial formulation analysis are shown in Table 1.

The calibration plots were found to be linear over the ranges 200-1000 and 200-700 ng/band for TEL and ATV, respectively. Results of validation parameters are shown in Table 2.

The results ofprecovery studies are shown in Table 3.

CONCLUSION

The validated HPTLC method employed hereproved to be simple, rapid, acurate, precise, sensitive and robust and can thus be used for routine analysis of TEL and ATV in a combined tablet dosage form.

ACKNOWLEDGMENTS

The authors wish to express their gratitude to Glenmark Pharmaceuticals Ltd., Nasik, India) for the sample of pure telmisartan, and to Hetero Drags Ltd. (HP, India) for the sample of pure atorvastatin calcium. The authors are also thankful to Dr. K. G. Bothara, Principal, AISSMS College of Pharmacy forproviding necessary facilities and his constant support.

 

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(Received: June 1, 2009 - Accepted: July 28, 2009)

* e-mail: santoshvgandhi@rediffmail.com