Simultaneous Estimation of Telmisartan and Indapamide in Bulk and Capsule Dosage Form by Reverse Phase High Performance Liquid Chromatography

 

Jawed Akhtar*, B. Srivastava and Parth Bhatt

School of Pharmaceutical Sciences, Jaipur National University, Jagatpura, Jaipur, Rajasthan.

*Corresponding author: jawed_pharma@yahoo.com

 

ABSTRACT:

A selective and sensitive reverse phase high performance liquid chromatography (RP-HPLC) method has been developed for the separation and quantification of telmisartan and indapamide in capsule dosages form has been fist developed and validated. Quantification carried out using Stainless Steel C₁₈ 130 x 4.6, 5µm column as a stationary phase and mobile phase comprised of 50mM KH₂PO₄, Acetonitrile and methanol in proportion of 50:20:30 (v/v/v) with pH adjusted to 3.0 ± 0.1 by using o-phosphoric acid. The flow rate was 1.0 ml/min and monitored at 280 nm. The retention time for telmisartan and indapamide were 11.1 and 4.458 minutes, respectively. The method was validated in terms of linearity, precision, accuracy, ruggedness, and specificity, limit of detection and limit of quantification. The linearity (r2) and percentage recoveries of telmisartan and indapamide were 0.9998 and 99.85 μg/ml and 0.9988 and 99.91 % respectively. The proposed method is suitable for simultaneous determination of telmisartan and indapamide in capsule dosage form.

 

 

1. INTRODUCTION:

Telmisartan, 2-(4-{[4-methyl-6-(1-methyl-1H-1,3-benzodiazol-2-yl)-2-propyl-1H-1,3-benzodiazol-1-yl] methyl} phenyl) benzoic acid, is a white crystalline powder, slightly soluble in water but freely soluble in alcohol and 1N NaOH solution. Telmisartan is an angiotensin II receptor antagonist used for hypertension. Indapamide is a benzamide- Sulfonamide-indole. It is a thiazide-like diuretic and it is used as an antihypertensive and a diuretic. Chemically it is known as 4-chloro-N-(2-methyl-2,3-dihydroindol-1-yl)-3-sulfamoyl-benzamide. Even though various methods reported in the literature for estimation of Telmisartan^1-9 and Indapamide^10-17 individual or in combination with other drugs no method had been reported so far for simultaneous estimation of these two drugs using HPLC in capsule dosage forms. The present study was aimed at the simultaneous estimation of telmisartan and indapamide by HPLC method. This method was validated according to the ICH guidelines¹⁹.

 

2. EXPERIMENTAL:

2.1. Instrument:

A HPLC (LC-20AD, Shimadzu, Japan) connected to computer loaded with spinchrom chromatographic software. System was coupled with SPD-20A prominence UV/Vis detector. All weights were taken on semi microbalance (Shimadzu -AX -200 electronic balances)

 

2.2. Reagents and chemicals;

Telmisartan and Indapamide were obtained as gift sample from Zydus Cadila Healthcare Ltd., Ahmedabad (Gujarat). Potassium dihydrogen phosphate, and potassium hydroxide were A.R. grade from Merck chemicals Mumbai, India. Acetonitrile and milli Q water were HPLC grade supplied by Merck chemicals Mumbai, India.

 

2.3. Chromatographic conditions:

A Stainless Steel C₁₈ 130 x 4.6, 5µm column was used as the stationary phase. The mobile phase comprised of 50mM KH₂PO₄, Acetonitrile and methanol in proportion of 50:20:30 (v/v/v) with pH adjusted to 3.0 ± 0.1 by using o-phosphoric acid. Injection volume was 20 µl and run time was 15min and flow rate 1.0 ml/min. The column was maintained at ambient temperature and the eluent detected at 280 nm.

 

2.4. Standard preparation:

Standard stock solution (300µg) of Telmisartan and (150µg) of Indapamide were prepared separately in methanol. The Working standard solutions were prepared and further diluted in methanol to contain a mixture of Telmisartan and Indapamide in over the linearity range from 18- 42 μg/ml and 9-21 μg/ml respectively.

 

Figure 1: Typical chromatogram of Telmisartan and Indapamide

 

Table No.1: System Suitability

S. No.	Parameter	Telmisartan	Indapamide
1	Theoretical Plate	5862	4475
2	Asymmetry of the peak	1.03	1.01
3	Retention time	11.105	4.42

 

2.5. Sample preparation:

Twenty capsules weighed and the average weight taken. Tablets of telmisartan  and indapamide were separately crushed. Powder of telmisartan tablets equivalent to 75 mg of Telmisartan was weighed and transferred to 100ml volumetric flask. Few ml of methanol was added, mixed and made up the volume with methanol (solution A). powder of indapamide tablets equivalent to 7.5 mg of indapamide was  separately weighed and transferred to a 20 ml volumetric flask. 10 ml of methanol was added to dissolve and mixed. volume was made up the with methanol (solution B). 10 ml of solution A and solution B were transferred to a 250 ml flask. 100 ml of methanol was added, mixed and the volume made up to 250 ml with methanol. The solution was filtered through 0.45µ nylon filter.

 

3. RESULTS AND DISCUSSION:

The proposed HPLC method required fewer reagents and materials, and it is simple and less time consuming. This method could be used in quality control test in pharmaceutical industries. The chromatograms of Telmisartan and Indapamide were shown in (fig. 1).There was clear resolution between Telmisartan and Indapamide with retention time of 11.1 and 4.458 minutes respectively.

 

3.1. Validation of the method:

3.1.1. System suitability:

The R_t values, capacity factor, resolution, theoretical plates/meter, and peak symmetry were calculated for the standard solutions. The values obtained demonstrated the suitability of the system for the analysis of the above drug combinations System suitability parameters might be fall within ± 3% standard deviation range during routine performance of the method. The summary of the system suitability results were showed in the (table 1).

 

3.1.2. Linearity:

The response for the detector was determined to be linear over the range of 18-42 μg/ml (18, 24, 30, 36, and 42) for Telmisartan and 9-21 μg/ml (9, 12, 15, 18, and 21) for Indapamide. Each of the concentration was injected in duplicate to get reproducible response. The calibration curve was plotted as concentration of the respective drug versus the response at each level. The proposed method was evaluated by its correlation coefficient and intercept value calculated in the statistical study. They were represented by the correlation co-efficient in (table 2).

 

3.1.3. Precision and accuracy:

The accuracy of the method was determined by recovery experiments. The recovery studies were carried out 6 times and the percentage recovery and % relative standard deviation was calculated. From the data obtained, recoveries of standard drugs were found to be accurate (table 2).The %RSD of interday and intraday precision obtained was less than 2% for both the drugs. The intraday and interday precision of Telmisartan was 0.031 and 0.0486 and Indapamide was 0.049 and 0.039 respectively. From the data obtained, the developed HPLC method was found to be precise and accurate.

 

3.1.4. Specificity of the method:

The chromatograms of the telmisartan and indapamide in standard and placebo were recorded. In the chromatograms of the formulations, some additional peaks were observed which may be due to excipients present in the formulations. These peaks however did not interfere with the standard peaks, which demonstrate that the assay method is specific. Furthermore, the purity of the peaks was studied by peak purity studies. The results revealed that the peak is free from interferences, which shows that the HPLC method is specific.

 

3.1.5. Detection and Quantification limits:

The limit of detection (LOD) and limit of quantification (LOQ) of the developed method was determined by injecting progressively low concentrations of the standard solutions using the developed method. The LOD is the lowest concentration of the analyte that can be detected with signal to noise ratio (1:3) and LOQ is the lowest concentration that can be quantified with acceptable precision and accuracy with signal to noise ratio (1:10). The LOD of telmisartan and indapamide found to be 0.006 μg/ml and 0.078 μg/ml respectively. The LOQ of telmisartan and indapamide found to be 0.0197 μg/ml and 0.236 μg/ml respectively.

Table No.2: Summary of analytical method validation

S. No	Parameters	Acceptance criteria	Telmisartan	Indapamide
1	Linearity	R2 = 0.995 to 1.0	0.9998	0.9988
2	Specificity	No interference with placebo	Specific	Specific
3	Accuracy (Recovery Studies)	Recovery : 98.0 to 102.0%	99.85%	99.91%
4	Precision
	Intraday (n=6)	RSD NMT 2.0 %	0.031	0.049
	Interday (n=6)	RSD NMT 2.0 %	0.048	0.039
5	Robustness (pH)	NMT + 1.0 %	0.3%	0.5%
6	Limit of detection (μg/ml)	.....................................	0.006	0.078
7	Limit of quantitation (μg/ml)	.....................................	0.019	0.236

 

 

3.1.6. Robustness:

The robustness of the method was studied by deliberate changes in the method like percentage organic content, alteration in pH of the mobile phase, changes in the wavelength. It was observed that there was no marked changes in the chromatograms demonstrate that the HPLC methods have developed are robust.

 

4. CONCLUSION:

This method is simple, specific and easy to perform and requires short time to analyze the samples. Low limit of quantification and limit of detection makes this method suitable for use in quality control. This method enables simultaneous determination of telmisartan and indapamide because of good separation and resolution of the chromatographic peaks. The method was found to be linear, precise, accurate, rugged and robust.

 

5. ACKNOWLEDGEMENTS:

The authors are thankful to Zydus Cadila Healthcare Ltd., Ahmedabad (Gujarat) for providing the gift samples of telmisartan and indapamide.

 

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Received on 20.05.2011          Modified on 07.06.2011

Accepted on 06.12.2011         © RJPT All right reserved