Spectrophotometric Method for Analysis of Metformin Hydrochloride

Indian Journal of Pharmaceutical Sciences 100 January February 2009 The limit of detection and limit of quantitation for artemisinin were calculated to be 25 ng/spot and 75 ng/spot respectively. The accuracy of the method was evaluated by % recovery (standard addition method) of the drug. The average recovery was found to be 99.60 with average % RSD. value of 0.27 (Table 3). The developed HPTLC method was applied to the analysis of artemisinin in capsule dosage form (Table 4). The mean % recovery value of 99.34 was obtained with % RSD value of 0.19. The values of S.D. or % RSD and coefficient of correlation were within the prescribed limit of 2% showing the high precision of the method. Hence, this indicates the suitability of the method for the routine analysis of artemisinin in bulk and pharmaceutical dosage forms. The developed HPTLC method was compared with HPLC method. The HPLC[10] method gave a mean % recovery of 99.68 ± 0.18, which agrees with values obtained by the proposed method. ACKNOWLEDGEMENTS

The limit of detection and limit of quantitation for artemisinin were calculated to be 25 ng/spot and 75 ng/spot respectively.The accuracy of the method was evaluated by % recovery (standard addition method) of the drug.The average recovery was found to be 99.60 with average % RSD.value of 0.27 (Table 3).The developed HPTLC method was applied to the analysis of artemisinin in capsule dosage form (Table 4).The mean % recovery value of 99.34 was obtained with % RSD value of 0.19.The values of S.D. or % RSD and coefficient of correlation were within the prescribed limit of 2% showing the high precision of the method.Hence, this indicates the suitability of the method for the routine analysis of artemisinin in bulk and pharmaceutical dosage forms.The developed HPTLC method was compared with HPLC method.The HPLC [10] method gave a mean % recovery of 99.68 ± 0.18, which agrees with values obtained by the proposed method.Metformin hydrochloride, chemically 1, 1-dimethylbiguanide hydrochloride [1] (C 4 H 11 N 5 .HCl) is white crystalline powder, hygroscopic and freely soluble in water, used as a hypoglycemic drug [2] .Literature survey reveals that only few methods like HPLC and GC have been reported for estimation of the metformin hydrochloride in pharmaceutical formulations and biological fluids [3][4][5][6][7][8][9] .Official method includes UV spectrophotometric method for estimation of the drug from the tablets [1] .However no colorimetric methods are reported for estimation of metformin hydrochloride in bulk and in formulations.
The present work describes a new simple spectrophotometric method based on the reaction between amino group of metformin hydrochloride with ninhydrin to form a violet colored complex, which shows absorption maxima at 570 nm.
The reference standard of metformin hydrochloride was procured as gift sample from Micro Labs, Bangalore and tablets (Obimet 500 mg, Kare Labs Pvt. Ltd.Goa) were utilized for the study.Ninhydrin and all other chemicals, solvents utilized were of AR grade.A double beam spectrophotometer (Shimadzu-UV-1601) was employed for measurement of absorbance.
A standard solution of metformin hydrochloride was prepared by dissolving 100 mg of the drug in 100 ml of distilled water and further diluted with water to get concentration of 100 μg/ml.Twenty tablets were weighed, powdered and the powder equivalent to 100 mg of metformin hydrochloride was accurately weighed, dissolved in 100 ml of distilled water, filtered through Whatmann filter paper No: 41 and diluted further to get a concentration of 100 μg/ml.
To a series of (S 1 , S 2 , S 3 , S 4 , S 5 ) 25 ml volumetric flasks, aliquots of 2.0 to 4.5 ml of the standard solution of metformin hydrochloride, 1.5 ml of 5M NaOH, 2.2 ml of 1% ninhydrin solution and 10 ml of water was added, heated on a water bath for 30 min, cooled and volume adjusted to 25 ml with water and the absorbance of the solution in each flask was measured at 570 nm against reagent blank.The absorbance of sample solution was also measured and the amount of metformin hydrochloride present in tablet formulation was determined by extrapolating from the calibration curve.The results are shown in the Table 1.In order to ascertain the suitability and reproducibility of the proposed method, recovery studies were carried out by adding known quantities of standard metformin hydrochloride to the previously analyzed sample and the mixtures were reanalyzed by the proposed method.The results are shown in the Table 2.The percentage recovery of metformin hydrochloride was found in the range of 97-100% indicating that there is no interference by the excipients in the method.

TABLE 4 : ANALYSIS OF MARKETED FORMULATION OF ARTEMISININ BY HPTLC AND HPLC METHOD
The developed HPTLC method was compared with HPLC method.The mean % recovery after analysis by HPLC agrees with values obtained by developed HPTLC method.(n=3)

TABLE 2 : RECOVERY STUDIES OF METFORMIN HYDROCHLORIDE
Table showing % recovery of metformin hydrochloride by the proposed method.*Average of three determination