New Developed Spectrophotometric Visible Analysis for Metformin Hydrochloride in Tablets of a Pharmaceutical

The main aim of this research was to find and develop a new spectrophotometric method for Visible analysis of Metformin hydrochloride in a pharmaceutical. The method was based on the quantitative reaction of metformin hydrochloride with 0.1% beta-naphthol alkaline solution in the presence of 5% sodium nitrite and 15% hydrochloric acid by resting in cold conditions for 25 minutes. The following was observed: the quantitative formation of an intense yellow azo dye with an absorption maximum at λ = 408 nm, which was subsequently dosed in relation to double distilled water as a blank. Method was linear over the studied concentration range between 0,80 μg/mL – 8,00 μg/mL. Linear regression coefficient was R² = 0,9994 , R² ≥ 0,9990 and correlation coefficient R = 0.9997, R > 0.9990; both fit perfectly within the normal limits. Limit of Detection (LOD) = 0,17496 μg/ mL, and limit of quantitation (LOQ) = 0,5832 μg/ mL, LD < 1 and LQ < 1 . Standard Error of the regression line was SE = 0.0065902, SE << 1, which had a very small value that was statistically accepted. Pure Metformin hydrochloride content found was 998.9858 mg in tablet, very close to the official stated amount of 1000 mg pure Metformin hydrochloride on extended-release tablet. The relative percentage deviation of the calculated amount 998.9858 mg was 0.1014% below the official reference value of 1000 mg and fell below the maximum average percentage deviation allowed (± 5%) imposed by the Romanian European Pharmacopoeias Rules.