Cadmium species in marine short-necked clam analyzed by size exclusion chromatography hyphenated respectively with inductively coupled plasma mass spectrometry and electrospray ionization quadrupole - time of flight mass spectrometry

To date, the speciation analysis of heavy metals in organs is still a challenge because these species are labile in vitro and scarce of the reference materials. In the present study, cadmium (Cd) species in marine shellfish were investigated with size exclusion chromatography (SEC) hyphenated with inductively coupled plasma mass spectrometry (ICP-MS), by which three Cd species in marine short-necked clam were observed. After pre-fractionation with a home-made Sephadex column, the Cd binding species were further characterized with SEC coupled with electrospray ionization quadrupole - time of flight mass spectrometry (ESI-Q-TOF-MS). The results showed that Cd species with 32,695 Da was the maximum Cd-binding molecule in the clam. Several metallothionein (MTs)-like Cd-binding proteins including a main species with molecular weight of 19,236 Da were observed. Some small Cd species with molecular weights less than 1000 Da were also observed in the clam. In order to verify the reliability of the two hyphenated methods, a standard reference material of Zn-binding MTs was analyzed at the same conditions. The results demonstrated that the two hyphenated methods of SEC-ICP-MS and SEC-ESI-Q-TOF-MS were practical to characterize the Cd species in marine shellfish.