Speciation Analysis of Cadmium in Marine Bivalves by Size Exclusion Chromatography-High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry

The speciation analysis of cadmium in the scallop (Chlamys farreri, C. farreri) with high Cd accumulation capability and the clam (Ruditapes philippinarum, R. philippinarum) with low Cd accumulation capability was first conducted by size exclusion chromatography-high performance liquid chromatography-inductively coupled plasma mass spectrometry (SEC-HPLC-ICP-MS), and in vitro whole-bionic digestion model was used to determine the cadmium speciation in two bivalves under the action of saliva, the acidity of stomach and intestine with in organic and organic components and digestion enzymes. The results showed that the total cadmium content in C. farreri was almost 10 times in R. philippinarum. Three Cd species, metallothionein (MT)-Cd, glutathione (GSH)-Cd and cystein (Cys)-Cd were detected in C. farreri, and two Cd species, MT-Cd and GSH-Cd were detected in R. philippinarum. According to the different peak areas, MT-Cd and GSH-Cd content in C. farreri was about 5.6 and 2.0 times of those in R. philippinarum respectively. Using in vitro whole-bionic digestion model, one unknown Cd species with small molecule (named Cd-X) was detected in whole-bionic digestion of gastric extracts, and four Cd species (mainly MT-Cd) were detected in the whole-bionic digestion of intestine extracts for C. farreri; however, for R. philippinarum, the unknown Cd-X was the main Cd species in both gastric and in testinal extracts. The experiment also proves that Cd can be separated from MT-Cd, GSH-Cd and Cys-Cd under the effect of the whole-bionic digestion of stomach and intestine.