1933Algae celk were successfully lmmoblllzed on a sllka substrate and used In a chromatographlc oeparatlon procedure that removed Pb from synthetlc solutlons. Characterlzatlon of the rerln In a chromatographlc extraction mode revealed acceptable flow rates and efflclent metal strlpplng by both HN03 and HCI. VarlaMllty arroclated wlth the growth, harvestlng, Immoblllzatlon, and column packlng procedures were evaluated. Results revealed excellent reproduclblllty for the lmmobllltatlon procedure, and the greatest source of varlatlon was arroclated wlth the algae growing process. The adsorption capaclty of the algae redn declined by 15 % over 20 adsorptlon-elutlon cycles, and attempt8 to ldentlfy and control the source (8) of the degradatlon were not succesdul. EquUikkrm parameters govemlng the metal adsorption process were obtalned by Schatchard analyrk, of the Pb blndlng data for both the free and lmmoMllzed algae. Comparlson of the extrapolated saturatlon values for the free (449 f 49 pmol of dtes/g of algae) and Immoblllzed algae (278 f 25 pmol of dtes/g of algae) reveal a 40 % loss of adsorptlon efflclency as a result of the Immoblllzatlon procedure. However, close agreement of the equlllbrlum constants calculated from the slope of the Wed regredon lines at hlgh Pb concentratlons for free (0.031 f 0.003) and lmmoblllzed (0.025 f 0.002) algae Indicate the Immoblllzatlon process ha8 mlnknal effeci on the Integrity of the remalnlng adsorption sltes. The dendty of adsorptlon 8Hes on the algae resln was also measured by a chromatographlc procedure (267 f 6 pmol of sltes/g of algae) and the results are In good agreement wlth the Scatchard method of data analysls.

Poly(l-cysteine) (PLC) was successfully immobilized on controlled-pore glass (CPG) and used in a flow injection system incorporating a microcolumn for separation of Cd from synthetic solutions. On-line breakthrough curves were used to study the effect of pH, concentration, and influent flow rate on Cd adsorption. The Cd breakthrough experiments revealed a significant strong-site capacity as well as weaker binding sites that showed a dependence on influent concentration. In addition, increased capacity was observed at more alkaline pH values. The flow rate studies showed nonequilibrium conditions existed for Cd binding at flow rates of 0.55−3.75 mL/min, with decreased capacity for faster flow rates. Elemental analysis of immobilized PLC for sulfur estimated 6.8 × 10-6 mol of PLC/g of CPG and the calculated mole ratio of Cd to PLC was 6.2:1 at pH 9. Stability constants governing the Cd adsorption by PLC were obtained by a nonlinear least-squares analysis of the Cd binding data and revealed at least four classes of binding sites were present and that the stable Cd complexation observed for the free molecule was retained by immobilized PLC. Stability constants for the most stable sites were estimated using EDTA and en as competing ligands and resulted in two sites:  K 1 = 1 × 1013 and K 2 = 109−1011 with capacities of n 1 = 1 μmol/g and and n 2 = 6 μmol/g, respectively. Two weaker binding sites were also identified and represented by stability constants of K 3 = 1 × 106 and K 5 = 2 × 104 with site capacities of n 4 = 20 μmol/g and n 5 = 10 μmol/g, respectively.

Poly(-cysteine) (PLC ) and 8-hydroxyquinoline (8HQ) were immobilized on controlled-pore glass and used in a flow injection system for the separation of Cd, Pb and Cu from synthetic sea-water, Co and Ni matrices as well as CRM sea-water. Both resins allowed for the quantitative recovery of 50 mg L−1 Cd and Pb in synthetic sea-water. However, low recoveries of 2-4% and 40-50% were observed using 8HQ for the separation of 50 mg L−1 Cd and Pb, respectively, from a 10 000-fold excess of Co and Ni, while PLC maintained quantitative recoveries. Neither 8HQ nor PLC showed reproducible or complete recoveries of Cu2+ from the columns using the typical means for stripping (1 M HNO 3 ). On-line breakthrough experiments showed that 8HQ had a significant strong binding site capacity for Cd, Pb, Cu, Co and Ni. PLC also had strong sites for Cd, Pb and Cu but showed only weak binding of Co and Ni. The selectivity of PLC against these harder acid metals allowed for quantitative recovery of Cd, Pb and Cu in Co and Ni matrices. Extracting low level spikes of Cd and Pb from CRM sea-water (CASS-1 and NASS-2) tested the application to 'real' samples. Recovery efficiencies of Cd were high for both CRM matrices studied. Pb recovery was good for CASS-1; however, recovery from NASS-2 was unexpectedly low. Mass transfer limitations were observed for both resins in the flow system, resulting in apparent decreased capacities at faster flow rates. Stability constants governing Cd adsorption by PLC and 8HQ were obtained by a non-linear least-squares regression analysis of the Cd binding data and revealed that at least four classes of binding site were present on both resins. Stability constants for the most stable sites were estimated using EDTA or ethylenediamine (en) as competing ligands. 8HQ had no sites that were competitive with EDTA, whereas PLC had an EDTA-competitive site with a stability constant of 1×1013 and a capacity of 1 mmol g−1. Both PLC and 8HQ had sites that were stronger than Cd(en) 2 with estimated stability constants ranging from 109 to 1011. Weaker sites on the resins had stability constants that ranged from 104 to 106. Cd was used to demonstrate the viability of this method for stability constant determination as it is well characterized for both 8HQ and PLC.

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Recently, a significant amount of work has focused on metal binding by natural systems for various applications. This review will focus on the utility of amino acids, short peptides, and proteins that have been immobilized onto solid supports for use in metal binding, These systems include single amino acids, poly-amino acids, and peptides immobilized onto supports such as silica, polymer resins, and membranes. Also included are the studies involving the use of immobilized amino acids in ion-exchange chromatograph