Mean slope from a set of 8 standard curves for hepcidin-25. The standard curves using synthetic hepcidin-25 were made using serial dilutions from a 100-mM stock concentration. Highly linear relationships between the peak intensities of 2789 m/z and the concentration of synthetic hepcidin-25 were obtained in a range from 4 nM to 256 nM in intra-assay. Eight replicates were done within-day. Dots and bars indicate means and SDs, respectively.