Zero order and area under curve spectrophotometric methods for determination of Omeprazole capsules in pharmaceutical formulation

Simple, fast and reliable spectrophotometric methods were developed for determination of Omeprazole in bulk and pharmaceutical dosage forms. The solutions of standard and the sample were prepared in Methanol. The quantitative determination of the drug was carried out using the zero order derivative values measured at 303 nm and the area under the curve method values measured at 300-305 nm (n=2). Calibration graphs constructed at their wavelengths of determination were linear in the concentration range of Omeprazole using 210μg/.ml (r2=0.9985 and r2=0.9959) for zero order and area under the curve spectrophotometric method. All the proposed methods have been extensively validated as per ICH guidelines. There was no significant difference between the performance of the proposed methods regarding the mean values and standard deviations. Developed spectrophotometric methods in this study are simple, accurate, precise and sensitive to assay of Omeprazole in tablets.


Introduction
Omeprazole is chemically known as 6methoxy-2-[(4-methoxy-3, 5-dimethylpyridin-2-yl) methylsulfinyl]-1Hbenzimidazole. Omeprazole is a used as an antiulcer drug and against other acidrelated diseases. [1] This blocks the final and common step in gastric acid secretion. Literature survey reveals that USP 2007 and IP 2007 [2] [3] report HPLC method for assay of omeprazole. Analytical methods reported for the estimation of omeprazole is HPLC [4][5][6][7][8][9], LC-MS [10][11]. To our notice, noUVspectrophotometric method using Zero Order and Area under Curve (AUC) has been reported for the determination of Omeprazole in bulk and tablets.Hence an attempt has been made to develop new Zero Order and Area under Curve Spectrophotometric method for estimation of Omeprazolein bulk and pharmaceutical formulations with good accuracy simplicity, precision and economy.

Area under curve (Area calculation)
Area under curve method involves the calculation of integrated value of absorbance with respect to the wavelength between two selected wavelengths such as λ1 and λ2 representing start and end point of curve region. The area under curve between λ1 and λ2 was calculated using UV probe software. In this study area was integrated between wavelength ranges from 300 to 305 nm.
Where, α is area of portion bounded by curve data and a straight line connecting the start and end point, β is the area of portion bounded by a straight line connecting the start and end point on curve data and horizontal axis, λ1 and λ2 are wavelength range start and end point of curve region [12].

Assay Procedure
Twenty tablets each containing 20mg of Omeprazole were weighed crushed to powder and average weight was calculated. Powder equivalent to 10mg of Omeprazole was transferred in 100 ml of volumetric flask. A 50 ml of Methanol was added and sonicated for 15minutes. Then solution was further diluted up to the mark with Methanol. The solution was filtered using Whatmann filter paper no. 41; first 5 ml of filtrate was discarded. This solution was further diluted to obtain 15µg/mL solution with water subjected for UV analysis using Methanol as blank. Appropriate dilutions were made with methanol from stock solution for both zero order and area under the curve spectrophotometric methods. www.ssjournals.com

Results and Discussion
The zero order and area under the curve spectra for Omeprazolewere recorded at the wavelength of 303nm and 300-305nm respectively [ Fig. 2 and 3].

Linearity and Range
Under the experimental conditions described, the graph obtained for zero order and area under the curve spectra showed linear relationship.
Regression analysis was made for the slope, intercept and correlation coefficient values. The regression equations of calibration curves were y=0.0056x+0.0097(r 2 =0.9985) at 303nm for zero order derivative spectrophotometry and y=0.0005x-0.0009 (r 2 =0.9959) at 300-305nm for area under the curve spectrophotometry. The range was found to be 2-10μg/ml for both zero order and area under the curve spectrophotometric methods. Abs.

Accuracy
To study the accuracy of the proposed methods, and to check the interference from excipients used in the dosage forms, recovery experiments were carried out by the standard addition method. The accuracy for the analytical method was evaluated at 80%, 100% and 120% levels of 15µg/ml standard solution. For Area under curve (AUC) was measured in wavelength range 300-305 nm and For Zero order derivative at 303nm and results were obtained in terms of percent recovery. Three determinations at each level were performed and % RSD was calculated for each level.  IJASR|VOL 01|ISSUE 02|2015 www.ssjournals.com

Precision
To determine the precision of the method, Omeprazole solutions at a concentration of 10μg/ml were analysed each three times for both zero order and area under the curve spectrophotometric methods. Solutions for the standard curves were prepared fresh everyday (Table 4).

Sensitivity
The limit of detection (LOD) and limit of quantification (LOQ) were calculated by using the equations LOD = 3xσ/ S and LOQ = 10xσ/S, where σ is the standard deviation of intercept, S is the slope. The LOD and LOQ were found to be 0.4731μg/ml and 1.4339μg/ml respectively for zero order derivative and The LOD and LOQ were found to be 0.7691µg/ml &2.3307µg/ml for area under the curve methods respectively.

Analysis of the Marketed Formulation
There was no interference from the excipients commonly present in the tablets. The drug content was found to be 99.50% and 97.94% zero order and area under the curve spectrophotometric methods respectively. It may therefore be inferred that degradation of Omeprazole had not occurred in the marketed formulations that were analysed by this method. The low % R.S.D. value indicated the suitability of this method for routine analysis of Omeprazole in pharmaceutical dosage form (Table 4).

Conclusion
No UV or Area under Curve spectrophotometric methods have been described for the determination of Omeprazole. Therefore simple, fast and reliable derivative spectrophotometric methods were developed for the routine determination of Omeprazole. The developed methods can be concluded as accurate, sensitive and precise and can be easily applied to the pharmaceutical formulation.