HR: 0830h
AN: B51C-0966    [PDF]
TI: Application of Flow Field Flow Fractionation-ICP-MS for the Study of Uranium Binding in Cell Suspensions of Shewanella oneidensis
AU: * Jackson, B
EM: Jackson@srel.edu
AF: Savannah River Ecology Laboratory, University of Georgia PO Drawer E, Aiken, SC 29802 United States
AU: Seaman, J
EM: seaman@srel.edu
AF: Savannah River Ecology Laboratory, University of Georgia PO Drawer E, Aiken, SC 29802 United States
AU: Neal, A
EM: neal@srel.edu
AF: Savannah River Ecology Laboratory, University of Georgia PO Drawer E, Aiken, SC 29802 United States
AU: Ranville, J
EM: jranvill@mines.edu
AF: Colorado School of Mines, Department of Chemistry & Geochemistry, Golden, CO 80401 United States
AB: Field flow fractionation (FFF) is an aqueous size-based separation technique applicable to the separation of biomolecules, colloids, and bacteria. When interfaced on-line with ICP-MS detection, elemental data can be collected concurrently. In this study we employed hyperlayer- FFF methodology to separate cells of Shewanella oneidensis strain MR-1 from exopolymers present in washed cell suspensions. The cell suspension was injected into a thin channel through which a carrier solution (10mM NH$_{4}$Cl) is continuously pumped. A field is applied perpendicular to the direction of channel flow forcing the cells and other particles against an accumulation wall; in this case we used flow (Fl) FFF, where the perpendicular force is another fluid flow, known as the cross flow, pumped across two porous frits on either side of the channel. The cells experience hydrodynamic lift forces moving them from the accumulation wall into faster flowing zones within the laminar channel flow. Because these lift forces depend on particle diameter, size separation takes place as the cells flow down the channel. With a channel flow of 4 ml.min$^{-1}$ and a cross flow of 0.4 ml. min$^{-1}$ the cells eluted with a retention time of 5.2 minutes corresponding to an approximate equivalent spherical cell diameter of 1-2 æm based on calibration of the hyperlayer method with sized polystyrene beads. Cell suspensions were spiked with increasing concentrations of U to establish an adsorption isotherm and with fixed U concentrations at varying pH to establish a pH sorption isotherm. Elution of cells was detected by UV absorbance and the eluant exiting the UV detector was interfaced on-line to ICP-MS to detect U. A linear sorption isotherm was determined for U solution concentrations from 0.2 - 16 æM. The pH sorption isotherm showed maximum U sorption to S. oneidensis occurs at pH 5, in agreement with other batch sorption studies. A relatively large molecular compound, presumably a cell exudate, since the cells were determined to remain intact with microscopy, was identified by FFF (soluble constituents are not retained in hyperlayer FFF and thus elute in the void volume). This cell exudate complexed U and at higher pH the exudate appeared to have a greater affinity for U than the cell surface. Thus Fl-FFF interfaced with ICP-MS detection appears to be a powerful analytical technique for metal sorption studies with bacteria; analysis can be carried out on very small sample volumes (typical injection volume is 25 æL) and additional speciation information can be gained because soluble organic constituents of the cell suspension also elute from the FFF channel and are resolved from the cells. Other possible applications of Fl-FFF include competitive metal binding studies in mixed bacteria suspensions and mixed mineral-bacteria suspensions.
DE: 1065 Trace elements (3670)
DE: 1094 Instruments and techniques
SC: Biogeosciences [B]
MN: 2003 Fall Meeting