Kinetics of interaction of Cr(VI) and Cr(III) with serum constituents and detection of Cr species in human serum at physiological concentration levels.

A novel analytical method, based on monolithic convective interaction media (CIM) chromatography coupled to UV and inductively coupled plasma mass spectrometry (ICP-MS) detectors, was developed to investigate the kinetics of interactions of Cr(VI) and Cr(III) with serum constituents, and perform Cr speciation at physiological concentration levels. Cr(VI) was separated from Cr-transferrin (Cr-Tf) and Cr-albumin (Cr-HSA) on a CIM diethylamino (DEAE) column using linear gradient elution from 100% buffer A (50 mM Tris-HCl + 10 mM NaHCO, pH 7.4) to 60% buffer B (buffer A + 2 M NHCl) in 10 min at a flow rate of 1 mL min. Good column recovery of separated Cr species (close to 100%) and satisfactory method repeatability (RSDs below 8%) was obtained. Kinetics of interaction of Cr(VI) and Cr(III) with serum constituents were followed after human serum was doubly spiked with enriched Cr(VI) and Cr(III) solutions, and speciation analysis applied from 5 min up to 48 h after spiking. The results showed that in serum Cr(III) rapidly interacted with Tf, while Cr(VI) reduction was slow. 48 h after spiking, more than 90% of added Cr(III) was bound to Tf and the remaining 10% associated with HSA. About 20% of spiked Cr(VI) was still present in serum, while the resulting Cr(III) was bound predominantly to Tf. High sensitivity of the developed speciation procedure enabled detection of Cr-Tf complex as the main Cr species in human serum at physiological concentration levels. To the best of our knowledge, Cr-Tf concentrations in serum of unexposed individuals have not been reported yet.