Development and Validation of UV Spectrophotom-

Omeprazole (Figure 1) chemically (RS)-5-methoxy-2((4-methoxy-3,5-dimethylpyridin-2-yl) methylsulfinyl)-1Hbenzo[d]imidazole[1] is a proton pump inhibitor used is a benzimidazole derivative used in the treatment of dyspepsia, peptic ulcer disease, gastro esophageal reflux disease, laryngopharyngeal reflux and Zollinger–ellison syndrome [2]. In peptic ulcers, it suppresses gastric acid secretion by specific inhibition of the H+/K+-ATPase in the gastric parietal cell. Domperidone (Figure 2) chemically 5-chloro-1-{1-[3-(2-oxo2,3-dihydro-1H-1,3-benzodiazol-1-yl)propyl]piperidin-4-yl}2,3-dihydro-1H-1,3-benzodiazol-2-one is a dopamine antagonist with antiemetic and gastrokinetic properties used to treat nausea and vomiting. Domperidone facilitates gastric emptying and decreases small bowel transit time by increasing esophageal and gastric peristalsis and by lowering esophageal sphincter pressure [3]. Few analytical methods of HPTLC [4], HPLC [5-7] and UV Spectrophotometry [8-10] have been reported for the simultaneous determination of Omeprazole and Domperidone in combined pharmaceutical dosage forms.


Instrument
Shimadzu UV1800 Double Beam UV-Visible Spectrophotometer was used for spectral studies.

Chemicals and reagents
Standard drug samples of Omeprazole (API) and Domperidone (API) were obtained from Yarrow Chem Products, Mumbai, India. The commercial formulation of Omeprazole and Domperidone capsules were procured from the local market.

Preparation of standard stock solution
The standard stock solutions of OMP and DOM were prepared separately by dissolving accurately weighed 100 mg of drug in methanol and volume was made up to 100 mL with methanol to get concentration of 1 mg/mL From the stock solution prepare working standard solution of 100 µg/mL concentration in methanol for both drugs.

Determination of wavelength of maximum absorbance (λ max)
The standard solutions of both OMP and DOM were further diluted to get concentration of 10 µg/mL. These solutions were scanned in the wavelength region of 200-400 nm and the λ max was observed at 301 nm and 287.2 nm for Omeprazole and Domperidone respectively. The wavelength spectra of OMP and DOM in methanol are shown in (Figure 3 & 4) respectively.

Preparation of calibration curve
Working standard solutions were prepared for the Omeprazole and Domperidone from the standard solution of 100 µg/mL. Different aliquots were taken from standard stock solution and diluted with methanol separately to prepare 2 µg/mL, 4 µg/mL, 6 µg/mL, 8 µg/mL 10 µg/mL and 12 µg/mL solutions respectively. The absorbance values of Omeprazole and Domperidone were obtained at 301 nm and 287.2 nm respectively. The calibration curves were plotted with concentrations against absorbance and regression equation was calculated.

Assay of capsule dosage form
For the estimation of drugs in commercial formulations, twenty capsules containing 20 mg of Omeprazole and 10 mg of Domperidone were weighed and average weight was calculated. An accurately weighed portion of powder sample equivalent to one capsule weight was transferred into a 100 mL clean dry volumetric flask containing 70 mL of methanol. The contents of the flask were sonicated for 10 min and the volume was made up to the mark with a further quantity of the methanol to get a stock concentration of Omeprazole and Domperidone. Further pipette 5 mL of the above stock solution into a 10 mL volumetric flask and the volume was made up to the mark with the methanol.  found to be y=0.04736x+0.01546 and y=0.03534X+0.00279 (Table 1) respectively with a correlation coefficient (r2) of 0.99545 for OMP and 0.99680 for DOM. Precision of the method was studied by repeated measurements of drug solution and results showed lower %RSD values. The %RSD for intra-day precision and inter-day precision for OMP were found to be 0.25% and 0.35% respectively. The %RSD for intra-day precision and inter-day precision ( Table 2 & 3) for DOM were found to be 0.28 and 0.37 respectively. The percent recoveries for OMP and DOM were found to be 100.05% (Table 4) and 100.17 % (Table 5) respectively. The limit of detection (LOD) and limit of quantification (LOQ) for Omeprazole were found to be 0.15 µg/ mL and 0.47 µg/mL respectively. The limit of detection (LOD) and limit of quantification (LOQ) for Domperidone were found to be 0.80 µg/mL and 2.45 µg/mL respectively ( Table 6). The percentage purity for the assay of OMP and DOM were found to be 99.84% and 99.15% respectively (Table 7).

Conclusion
The UV spectrophotometric method for the simultaneous determination of Omeprazole and Domperidone in marketed formulations was developed and validated as per ICH guidelines. The satisfying recoveries, low correlation coefficient and assay results confirmed the suitability of proposed method for the routine quality control analysis for simultaneous determination of OMP and DOM in pharmaceutical formulations. The %RSD values for the proposed method reveals high degree of precision of method .The assay and validation results are satisfactory and