Capillary electrophoresis/laser-induced fluorescence detection of fluorescein as a groundwater migration tracer

Capillary electrophoresis (CE) has been applied to the determination of the groundwater migration tracer dye fluorescein based on laser-induced fluorescence (LIF) detection and compared to determinations obtained with traditional spectrofluorimetry. Detection limits of injected dye in the low parts per trillion (ppt) ranges have been accomplished with both CE/LIF based on the Ar ion laser and with a spectrofluorimeter. This approach was used for a real-world problem in determining groundwater migration between adjacent Resource Conservation and Recovery Act (RCRA) and Superfund sites by the Environmental Sciences Division in response to regional needs and as application of new analytical tools under development. Fluorescent dye was injected into source wells and then was determined in monitoring wells by extracting pads that adsorbed the dye or by directly determining the dye in the water using solid-phase extraction (SPE), a preconcentration technique. The approaches based on CE/LIF exhibits increased specificity over existing approaches due to the separation and unique migration time of the dye. Additional studies were aimed at achieving sub-ppt levels in the water using solid-phase extraction and field-amplified injection techniques.