[ICP-MS with octopole reaction system applied to isotopic analysis of iron in human fecal samples]

The study was aimed to evaluate the application of the quadrupole inductively coupled plasma mass spectrometer (ICP-MS) with collision/reaction cell octopole reaction system (ORS) to determine the iron stable isotope ratio in human fecal samples.

In a field trial on human metabolism, 3.0 mg per subject of iron with 57Fe enriched was orally administrated, and feces were collected by fecal monitoring. The isotope ratio of 57Fe to 56Fe in the prepared fecal sample was detected with the ORS-ICP-MS.

With the application of ORS-ICP-MS, interferences from the Ar plasma and the calcium-contained polyatomic ions could be eliminated. When the sample solution properly diluted, interferences from the matrix were too little to be noted. The relative stand deviation (RSD) of the long-term and short-term precision was < 0.3 %. From the changes of 57 Fe/56 Fe in the daily samples, a regularity of fecal iron outputs was presented, and the fractional iron absorption could be evaluated.

The ratio of 57 Fe to 56 Fe in the fecal sample could be accurately determined by the quadrupole ICP-MS with ORS, based on which the dietary iron absorption could be evaluated and the metabolism of iron in the human body could also be traced.