INTRODUCTION:

Pantoprazole is white to off white powder. Chemically it is 6-(difluoromethoxy)-2-{[(3,4-dimethoxypyridin-2-yl) methane]sulfinyl}-1H-1,3-benzodiazole. It is a proton pump inhibitor drug used for short-term treatment of erosion and ulceration of the esophagus caused by gastro esophageal reflux disease. Diclofenac Sodium 2-{2-[(2,6-dichlorophenyl)amino]phenyl}acetic acid. It is non-steroidal anti-inflammatory agent (NSAID) with antipyretic and analgesic actions. It is primarily available as the sodium salt. Diclofenac Sodium is official in IP¹ and USP². Literature survey revealed that simultaneous estimation of Domperidone and Pantoprazole by UV Spectrophotometery³, Three wavelength Spectrophotometric⁴ and HPLC⁵ methods.

First - order UV-derivative Spectrophotometery⁶ in the analysis of Omeprazole and Pantoprazole sodium salt and corresponding impurities. No Derivative spectrophotometric method for Simultaneous estimation of Pantoprazole and Diclofenac Sodium in combined pharmaceutical dosage form has so far been reported. The review of literature prompted us to develop a precise simultaneous method for the estimation of Pantoprazole and Diclofenac Sodium in combined dosage.

EXPERIMENTAL METHOD:

A double-beam UV-Visible spectrophotometer, model UV-1800 (Shimadzu, Japan) having two matched cells with 1-cm light path, was used to measure absorbance of the resulting solutions. Pantoprazole (Lincoln pharmaceutical limited) and Diclofenac Sodium (Torrent pharmaceutical limited) were produced from the market. Methanol was used as solvent.

Preparation standard stock solution (100μg/ml):

Accurately weighed 10 mg of Pantoprazole and 10 mg of Diclofenac sodium were transferred to two separate 100 ml volumetric flask. 50 ml methanol was added to the flask. The drug was dissolved with sonication and the final volume was adjusted with methanol up to the mark to prepare a 100 µg/ml stock solution of both drugs.

Preparation working standard solution:

Standard stock solution (100 µg/ml) of Pantoprazole and Diclofenac sodium were used as working standard solutions.

ANALYSIS OF FORMULATION:

Preparation of sample solution:

Twenty capsules were weighed accurately and emptied. Quantity of the powder equivalent to 2 mg of Pantoprazole and 7.5 mg of Diclofenac sodium was transferred into 100 ml measuring flask and dissolve it in methanol and sonicated for 20 minutes. The solution was filtered through Whatman filter paper No. 41 and the residues were washed thoroughly with methanol. The filtrate and washings were combined in a 100 ml volumetric flask and diluted to the mark with methanol to obtain final solutions of 20 µg/ml of Pantoprazole and 75 µg/ml of Diclofenac sodium.

Determination of wavelengths of maximum absorbance and wavelength of ZCP (Zero Crossing Point) for Pantoprazole and Diclofenac Sodium:

The working standard solutions were scanned in the range of 200 nm to 400 nm against methanol as a blank. Maximum absorbance was obtained at 291 nm and 282 nm and the ZCP were found to be at 291 nm and 282 nm for Pantoprazole and Diclofenac sodium, respectively in Figure 1 and Figure 2.

Fig 1: First order spectra for Pantoprazole

METHOD OF VALIDATION:

Calibration curve (Linearity):

Accurately measured working standard solution of Pantoprazole (0.5, 1.0, 1.5, 2.0 and 2.5 ml) and Diclofenac sodium (1.0, 1.5, 2.0, 3.0, and 5.0 ml) was transferred to separate 10 ml volumetric flasks and diluted up to the mark with methanol. Absorbance was measured at ZCP of Pantoprazole (291 nm) and ZCP of Diclofenac sodium (282 nm) for Diclofenac sodium and Pantoprazole respectively using methanol as a blank. The calibration curve was constructed by plotting absorbance versus concentration corresponding to each working standard solutions. Each reading was average of three determinations. A calibration curve was plotted over a concentration range from 5-25 µg/ml for Pantoprazole and 10-50 µg/ml for Diclofenac sodium.

Fig 2: First order spectra for Diclofenac Sodium

Table 1: Recovery studies of Pantoprazole and Diclofenac - Sodium

Drug	Amount taken (μg/ml)	Amount added (μg/ml)	Amount found (μg/ml) ± S.D (n=3)	% recovery ± S.D (n=3)
Panto-prazole	10	5	15.04 ± 0.29	100.27 ± 1.93
	10	10	19.87 ± 0.25	99.37 ± 1.25
	10	15	25.21 ± 0.80	100.84 ± 1.00
Diclo-fenac- Sodium	10	5	15.14 ± 0.32	100.98 ± 1.74
	10	10	20.74 ± 0.17	103.70 ± 0.85
	10	15	25.94 ± 0.10	103.77 ± 0.39

Table 2: Method validation parameters for Pantoprazole and Diclofenac Sodium

Parameters	Pantoprazole	Diclofenac Sodium
Calibration range	5-25μg/ml	10-50μg/ml
Detection limit	0.34μg/ml	0.42μg/ml
Quantitation limit	1.02μg/ml	1.30μg/ml
Slope	0.0008	-0.0009
Intercept	0.0001	-0.0013
Mean	99.79	103.98
Standard deviation	0.51	0.65
% RSD	0.51	0.63
Correlation coefficient r²	0.9987	0.9988
Intraday RSD, %	0.25-1.46	0.46-1.65
Interday RSD, %	0.25-1.96	0.067-1.18

Accuracy and Precision:

The accuracy of the method was determined by calculating percentage recoveries of Pantoprazole and Diclofenac sodium by the standard addition method. Known amounts of standard solutions of Pantoprazole and Diclofenac sodium (50, 100, and 150% level) were added to previously analyzed sample solutions.

The amount of Pantoprazole and Diclofenac sodium was analyzed by applying these values to the regression equation of the calibration curve. Method precision of the instrument was checked by repeatedly (n=6) measuring the absorbance of Pantoprazole (20 µg/ml) and Diclofenac sodium (20 µg/ml). The results were reported in term of %RSD which should not be more than 2%. Intermediate precision was evaluated in terms of intraday and interday precision by analyzing drug solutions 3 times on the same day and on different days over entire concentration range for both drugs. Results were reported in terms of %RSD.

Estimation of Pantoprazole and Diclofenac Sodium in Formulation:

Test solution from capsules which contain Pantoprazole (8.0, 10.0 and 12.0 µg/ml) and Diclofenac sodium (30.0, 37.5 and 45.0 µg/ml) were prepared and solutions were analyzed at the ZCP of Pantoprazole and Diclofenac sodium. Concentrations of both drugs were calculated from corresponding calibration curves which are shown in fig 1 and fig 2 respectively.

Recovery studies:

Accuracy of the method was assured by use of the standard addition technique, involving analysis of formulation samples containing 10 mg of both Pantoprazole and Diclofenac sodium to which certain amounts of authentic drugs were added. The resulting mixtures were assayed and the results obtained for both drugs were compared to those expected. Good recoveries with the standard addition method (Table 1) prove the accuracy of the proposed method.

RESULT AND DISCUSSION:

Absorbance for Pantoprazole and Diclofenac sodium were recorded at 291 nm (ZCP of Pantoprazole) and 282 nm (ZCP of Diclofenac sodium). The developed method was validated as per ICH guideline, data for which are shown in the table 1 and table 2.The method was applied for the determination of both drugs in pharmaceutical dosage form and its result is given in table 3.

CONCLUSION:

A validated derivative spectrophotometric method has been developed for estimation of Pantoprazole and Diclofenac sodium in combined pharmaceutical dosage form. The proposed method is simple, accurate and precise and the method is suitable for routine analysis of Pantoprazole and Diclofenac sodium in combined pharmaceutical dosage form. Detection and quantification limits achieved, describe that the method is sensitive. High recoveries and acceptable %RSD values confirms accuracy and precision of developed method. Assay results show that the method can be successfully applied for routine analysis of Pantoprazole and Diclofenac sodium in combined pharmaceutical dosage form.

REFERENCE:

1. Indian Pharmacopoeia, 1996; vol-1; 242.

2. United State Pharmacopoeia, National Formulary, USP 24, Asian Edition, 2006; 683.

3. Ravikumar P, Bhanuprakash P, Muralikrishna M, Santha MY, Asha CD. Simultaneous estimation of Domperidone and Pantoprazole in solid dosage form by UV Spectrophotometery. E- Journal of Chemistry 2006; 2(12): 142-145.

4. Kakde RB, Gedam SN, Chaudhary NK, Barsagade AG, Kale DL, Kasture AV. Three-wavelength spectrophotometric method for simultaneous estimation of Pantoprazole and Domperidone in pharmaceutical preparations. International Journal of Pharmtech Research 2009; 1(2): 386-389.

5. Reddy PB. Simultaneous HPLC estimation of Pantoprazole and Domperidone from tablet. International Journal of Chem Tech Research 2009; 1(2): 275-277.

6. Karlijkovic RK, Novovik D, Agbaba D. First-order UV-derivative Spectrophotometery in the analysis of Omeprazole and Pantoprazole sodium salt and corresponding impurities. Journal of Pharmaceutical and Biomedical Analysis 2003; 32(4-5): 1019-1027.

Received on 18.05.2012 Modified on 20.06.2012

Asian J. Research Chem. 5(7): July, 2012; Page 893-895