BioChain's iron concentration assay kit is a simple, direct and automation-ready assay for measuring iron in serum without pretreatment. The improved method utilizes chromogen that forms a blue colored complex specifically with Fe2+. Fe3+ in the sample is reduced to Fe2+, thus allowing the assay for total iron concentration. The intensity of the color is directly proportional to the iron concentration in the sample. The optimized formulation substantially reduces interference by substances in the raw samples.