**4.4 Speciation of heavy metal binding non-protein thiols in Agropyronelongatum by size-exclusion HPLC: ICP-MS**

In order to quantify the major of heavy metals (Pb, Cu, Cd, Co, Zn and Ni), three ionic separation column systems were evaluated [108]: (1) a cationic column (HPIC-CS2, Dionex) tested with two eluents (10 mMoxalic acid–7.5 mM citric acid; and 40 mM D-tartaric acid–12 mM citric acid); (2) an anionic column (HPIC-AS4, Dionex) evaluated with 25 mM oxalic acid as eluent; and (3) a bifunctional ionexchange column (Ionpac CS5, Dionex) which was also tested with two eluents (6 mM pyridine, 2,6-dicarboxylic acid; and 50 mM oxalic acid/95 mM lithium hydroxide
