An Improved Ferrozine-Based Protocol for Safe, Reproducible, and Accurate Quantification of Iron in Biological and Chemical Samples

Accurate quantification of iron is essential in biological, chemical, and nanomaterial research, yet commonly used ferrozine-based assays suffer from safety hazards, inconsistent reduction efficiency, and unstable absorbance readings. To address these issues, we systematically optimized the classical protocol and validated improvements that enhance both operational safety and analytical reproducibility. In this work, samples were digested using perchloric acid and hydrogen peroxide, reduced with hydroxylamine, and complexed with ferrozine, with all steps quantitatively evaluated to identify conditions that minimize variability. The optimized assay introduces three key refinements: combining the two traditional hydroxylamine additions into a single reduction step, extending the post-complexation incubation to 2 h to ensure complete formation of the Fe2+–ferrozine complex, and performing digestion exclusively in 5 mL screw-cap polypropylene tubes to eliminate tube-bursting events frequently observed with flip-cap formats. Kinetic analysis confirmed that absorbance at 562 nm reaches a stable plateau after 2 h, and the resulting standard curve exhibited excellent linearity (R2 = 0.9999). These improvements significantly enhance precision, safety, and ease of implementation. The refined method is broadly applicable and enables reliable quantification of iron in tissues, cultured cells, aqueous solutions, and iron-containing nanomaterials.