Simultaneous UV Spectrophotometric Method for Estimation of Sitagliptin phosphate and Metformin hydrochloride in Bulk and Tablet Dosage Form

Two simple, precise and economical UV methods have been developed for the simultaneous estimation of Sitagliptin phosphate and Metformin hydrochloride in bulk and pharmaceutical dosage form. Method A is Absorbance maxima method,which is based on measurement of absorption at maximum wavelength of 266nm and 232nm for Sitagliptin phosphate and Metforminhydrochloride respectively.Method Bis area under curve(AUC),in the wavelength range of 244-279 nm for Sitagliptin phosphate and 222-240nm for Metformin hydrochloride. Linearity for detector response was observed in the concentration range of 25-225µg/ml for Sitagliptin phosphate and 2-12µg/ml for Metformin hydrochloride. The accuracy of the methods was assessed by recovery studies and was found to be 99.64% and 98.98% for Sitagliptin phosphate and Metforminhydrochloride .The developed method was validated with respect to linearity,accuracy(recovery),precision and specificity.The results were validated statistically as per ICH Q2 R1 guideline and were found to be satisfactory. The proposed methods were successfully applied for the determination of for Sitagliptin phosphate and Metforminhydrochloride in commercial pharmaceuticl dosage form.

A comprehensive literature research reveals the lack of a spectrophotometric analytical method for simultaneous estimation of Sitagliptin and Metformin HCl in pharmaceutical formulations.
A successful attempt was made to develop accurate, precise and simple method of analysis for estimation of both the drugs in combined dosage form.

Materials:
Sitagliptinphosphate and Metforminhydrochloride was generous gift samples from Matrix Laboratory Limited (Hyderabad, India). Commercial Janumet tablets containing 50mg of Sitagliptin phosphate and 500mg of Metforminhydrochloride were purchased from local market and used within their shelf-life period. All other chemicals used were of analytical grade.

Instrumentation:
A Jasco double beam UV-visible spectrophotometer, Model:V-630, with affixed band width (2nm) and1-cm quartz cell was used for Spectral and absorbance measurements. In addition, electronic balance, micropipette and sonicator were used in this study.

Procedure:
Preparation of standard stock solution-Volume 4, Issue 6, November-December 2022 3 Standard stock solutions of each STG and MET was prepared by dissolving 100 mg of standard MET and 10 mg of standard STG separately in 10ml distilled water with vigorous shaking. A liquot in the range of 25-225µg/ml for STG and 2-12µg/ml for MET was prepared using this stock solution.

MethodA:Absorption Maxima Method
For the selection of analytical wavelength ,standard solution of STG and MET were scanned in the spectrum mode from 400 nm to 200nm separately.From the spectra of drug λ max of STG,266nm[ Fig

Simultaneous estimation of Sitagliptin phosphate and Metforminhydrochloride:
The wavelength maxima of Metformin HCl and Sitagliptin were determined and found to be 232 nm (λ 1 ) and 266nm (λ 2 ) respectively where there was no interference among the drugs. The over lain spectrum is shown in Fig.4. calibration curves were plotted as absorbance against concentration of STG and MET. The coefficient of correlation (r), slope and intercept values of this method are given in Table 1.

Application of the proposed methods for the determination of STG and MET in tablet dosage form:
For the estimation of drugs in the tablet formulation, 20 tablets were weighed and weight equivalent to 50mg of STG and 500mg of MET was transferred to 50ml volumetric flask and ultrasonicated for 20 minutes and volume was made up to the mark with distilled water. The solution was then filtered through a Whatmann filter paper (No.42) .The filtrate was appropriately diluted further. In Method-A, the concentration of STG and MET was determined by measuring the absorbance of the sample at 266nm and 232nm respectively in zero order spectrum mode. By using the calibration curve, the concentration of the sample solution was determined.

Validation of the developed methods 18 :
The methods were validated with respect to accuracy,linearity,precision and selectivity.
Accuracy:Accuracy of an analysis was determined by systemic error involved.Accuracy may often be expressed as % Recovery by the assay of known, added amount of analyte. It is measure of the exactness of the analytical method. Recovery studies carried out for both the methods by spiking standard drug in the powdered formulations 80% ,100%, 120% amount of each dosage content as per ICH guidelines.
Linearity:The linearity of measurement was evaluated by analyzing different concentration of the standard solution of STG and MET.Result should be expressed in terms of correlation co-efficient.

Precision:
The reproducibility of the proposed method was determined by performing tablet assay at different time intervals (morning, afternoon and evening) on same day (Intra-day assay precision) and on three different days(Inter-dayprecision). Result of intra-day and inter-day precision is expressed in% RSD.

RESULTS AND DISCUSSION
The methods discussed in the present work provide aconvenient and accurate way for analysis of Sitagliptin phosphate and Metformin hydrochloride in its bulk and pharmaceutical dosage form. Absorbance maxima of STG at266nm and MET at 232nm were selected for the analysis. Linearity fordetector response was observed in the concentration range of 25-225µg/ml for STG and 2-12µg/ml for MET.Percent label claim for STG andMET in tablet analysis was found in the range of 99.58% and 99.98% [

CONCLUSION
UV spectrophotometric method sfor Sitagliptin phosphate and Metforminhydrochloride were developed separately in bulk and tablet dosage form by, Absorbance maxima method and Areaunder curve method. Further,UV spectrophotometric methods for the simultaneous estimation of Sitagliptin phosphate and Metformin hydrochloride were in bulk and combined dosage form. The methods were validated as per ICH guidelines. The standard deviation and % RSD calculated for these methods are <2, indicating high degree of precision of the methods. The results of the recovery studies showed the high degree of accuracy of these methods. In conclusion, the developed methods are accurate, precise and selective and can be employed successfully for the estimation of STG and MET in bulk and pharmaceutical dosage form.