Journal of Analytical Atomic Spectrometry, 26(2), p. 334-340 (2011); doi:10.1039/C0JA00053A
Since its discovery the role of hepcidin as key regulator of iron homeostasis has been stressed by many authors. This peptide hormone of 25 amino acids, out of which 8 are cysteines, holds promise as a novel biomarker in iron metabolism disorders. In this work, we illustrate the progress of a new method for the analysis of hepcidin via sulfur detection using inductively coupled plasma mass spectrometry (ICP-MS) after capillary liquid chromatography for separation of the species. Three different ICP-MS-based strategies have been evaluated to overcome S polyatomic interferences: (1) a collision/reaction cell instrument with Xe as collision gas; (2) the monitoring of SO+ by adding O2 to the reaction cell and (3) a double focusing system (DF-ICP-MS). The latter one provided best limits of detection for S (7 ng mL−1) and good precision and accuracy to monitor S isotope ratios so it was used for hepcidin determination in urine samples by online isotope dilution. Quantitative recoveries of the peptide standard (101.7 ± 1.4%) are obtained with the proposed setup after controlling the column temperature (50 °C) and using the X-skimmer cone. Different sample clean-up procedures were studied in order to apply the developed quantitative methodology to urine samples. Multidimensional (dialysis + solid phase extraction) procedures provided best results yielding a 12-fold preconcentration factor. The obtained extracts were analyzed simultaneously by the developed capLC-ICP-MS setup and also by capLC-ESI-q-TOF for confirmation purposes. The results obtained revealed that ESI-q-TOF detection is more suitable for hepcidin determination in urine samples regarding both selectivity and sensitivity.