An analytical method for determination of total iron in pharmaceutical-grade intravenous iron colloidal complexes by Redox-Potentiometry

Iron carbohydrate complexes are colloidal dispersions made up of polynuclear Fe(III)-oxyhydroxide cores surrounded by a carbohydrate shell that stabilizes the complex in iron colloidal formulations. The current study provides an improved method that is precise, accurate, and linear for quantifying total iron in most Iron Carbohydrate Colloid Drug Products.Redox iodometry with a potentiometric determination is used to evaluate total iron in intravenous formulations. The visual indicator approach is more prone to fluctuations at endpoint calculations. Hence, the voltage potential approach is widely accepted as it is more accurate and sensitive. It tracks the actual change in activity that coincides with the equivalence point that is finally considered an endpoint. The principle is based on the idea that ferric iron in formulation reduces to ferrous iron in the presence of the iodide, which oxidizes to iodine. The released iodine is titrated using sodium thiosulfate.The proposed method was precise, with %RSD (relative standard deviation) not more than 1. The method was linear between 80% and 120%, with a linear regression of 0.999. The percent recovery ranged from 98.20 to 99.98 for the concentration ranges of 80-120. The method's robustness was checked by various analysts using different reagent grades.The proposed potentiometric determination method was precise, accurate, linear, and sensitive. The method was successfully validated, and the total iron content determined for commercial batches agrees with the iron claim on the label. Therefore, this method can be adapted widely for total iron content determination in any Intravenous formulation currently available on the market. The proposed method is more accessible at the Quality Control facilities on an industrial scale.