Development Method for Determination of Metronidazole in Pharmaceutical Preparation via Flow Injection Technique Using Phosphotungstic Acid as a Precipitant Agent

The applications of flow injection-turbidimetric technique for the determination of Metronidazole (MTZ) are described. The method is based on the using the phosphotungstic acid as a precipitating agent for MTZ to form a turbid solution of ion pair MTZ-phosphotungstic acid (PTA). Turbidity values were measured via locally made turbidimeter (6SX1-T-2D Solar Cell) that fabricated with flow injection system. Lots of chemical and physical parameters such as precipitant concentration, salts effect, flow rate and sample volume have been investigated. The results of proposed method show a relatively wide range of MTZ concentration (0.1-5.0) mmol. L-1 and correlation coefficient (r) = 0.9982. The detection limit that depends on the dilution of minimum concentration in drug variation curve is 0.946 g/sample while the limit of quantitation (L. O. Q) was 12.05 g/sample. The proposed method has good repeatability of 3.0 and 3.5 mmol. L-1 of MTZ solution and was found less than 1 % for n=6. The paired t-test value at 95 % confidence interval was conducted and the results indicate that there is no significant difference between the proposed and classical methods. The development method can be used for the routine and quantitative assay of MTZ in pharmaceutical dosages.