Quantitative colorimetric assay. This assay has high sensitivity and excellent specificity for detection of human FE. No significant cross-reactivity or interference between human FE and analogs was observed. Note: Limited by current skills and knowledge, it is impossible for us to complete the cross-reactivity detection between human FE and all the analogs, therefore, cross reaction may still exist. Sample types: cell lysates, plasma, serum, tissue homogenates. Range: 5 - 120 ng/ml. Precision: Intra-assay: CV%<15% Inter-assay: CV%<15%.