The mobilization of an element (e.g. Cr, Hg, As, Pb), as well as its bioavailability and toxicity within the biosphere, depends on its chemical form. On-line species separation and detection is an essential way to elucidate elemental mobilization parameters. Capillary electrophoresis (CE) has emerged as a strong separation technique for elemental speciation. The lack of stationary phase allows for a low likelihood of breaking metal-ligand bonds. CE requires small sample sizes and reagent volumes, and has high cost-efficiency. Non-destructive on-line elemental detection is feasible by X-ray fluorescence spectrometry (XRF). New developments in XRF low-power tube and electrically cooled detectors have made miniaturization of low-maintenance and cost-efficient XRF instrumentation available. Previous studies have shown the feasibility of benchtop CE-XRF setups with detection through the capillary wall. Long distances and optics in XRF-imaging setup are leading to a significant loss in excitation photons on the sample. The detection limits (DLs) obtained (ppm range) are not competitive enough to make it attractive for most applications. To enhance the fluorescence signal in CE-XRF, the optic will be removed and the distance to the X-ray tube will be decreased. The solid angle is thereby increased dramatically, and we expect a 10<sup>4</sup> gain in excitation radiation as a result. A detection cell with a silicon nitride window (&lt;200nm) will reduce scatter and absorption, with the greatest impact on signals for low Z elements (≤90% increase). Overall, DLs will likely decrease three orders of magnitude compared to systems using micro-XRF setups. Once the laboratory setup is successfully established, it will allow for a small footprint, cost-efficient, non-invasive sensitive and accurate instrument allowing for the analysis of elements in the liquid phase and provide excellent conditions for the study of dynamic change in oxidation state during elemental migration focusing on Cr, Hg, As, and Pb species.

Development of a novel CE-XRF system for elemental speciation

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.