Abstract Two biologically based ligands, cysteine (Cys) and poly- l -cysteine (PLCys), were coupled with Carbopack-X, a commercially available porous carbon surface after acid activation, through simple cross-linking techniques. The resulting Cys-X and PLCys-X systems are effective for metal binding with capacities in the range of 1–25 μmol metal/g column, depending on the metal tested. Both columns demonstrate similar selectivity for the soft and moderately soft acid metals such as Cd 2+ , Cu + , and Pb 2+ , probably as a result of the soft basic character of the thiol ligand side chains, and exhibit minimal binding of the harder groups IA and IIA metals. Even though PLCys-X and Cys-X displayed similar strong and weak binding characteristics, the PLCys-X system contained stronger binding sites than those possessed by Cys-X. The strongest site displayed by Cys-X has a binding constant of 1×10 9 , with the ability to compete for metal with moderately strong ligands such as ethylenediamine. However, the strongest PLCys-X site possessed a binding constant of about 10 13 , with the ability to compete for metals bound by very strong ligands such as EDTA. Both systems gave quantitative release of bound metals upon exposure to acid. Exposing the thiol-rich ligands to chemical reducing or oxidizing environments altered the metal binding characteristics of both columns, with at least a 50% decrease in metal binding on the oxidized columns due to thiol binding sites because of disulfide bond formation.