Tracer-Grade Rhodamine WT: Structure of Constituent Isomers and Their Sorption Behavior

Citations Over TimeTop 10% of 2001 papers

Abstract

Rhodamine WT (RWT), a fluorescent xanthene dye, is often used as a conservative tracer in aquifer characterization and as a surrogate or sorbing tracer for contaminant fate and transport. Quantitative tracing employing RWT is confounded by the presence of two major fluorescent constituents in the tracer-grade mixture. Here, we have confirmed that the two constituents are isomers of RWT, elucidated their molecular structures and their percent mass distribution in the tracer-grade mixture, and examined their individual sorption behavior onto soil solids. The energy-minimized geometry of the meta isomer indicates that it possesses a greater potential for (i) hydrophobic exclusion from bulk solution, (ii) electrostatic attraction to the solid phase, and (iii) surface complexation with surface-bound Al and Fe ions as compared with the para isomer. Hence, the meta isomer consistently sorbs to a higher extent onto the mineral phases examined. The para isomer has the potential to be a nearly conservative tracer, and the meta isomer has the potential to be a nonconservative tracer. To facilitate RWT use as a conservative tracer and comparison of tracer tests at different locations, we recommend modification of the RWT manufacturing process toward production of 100% of the para isomer. Alternatively, appropriately designed tests with tracer-grade RWT have the potential for simultaneous estimation of hydraulic parameters and contaminant fate and transport.

Related Papers

• → A new fluorescent and colorimetric probe for Cu2+ in live cells(2012)53 cited
• → A water-soluble rhodamine B-derived fluorescent probe for pH monitoring and imaging in acidic regions(2017)18 cited
• → A procedure for enriching and cleaning up Rhodamine B and rhodamine WT in natural waters, using a Sep-pak C18 cartridge(1984)19 cited
• → Effect of Inorganic Ions on the Discoloration of Rhodamine B by the Fenton Process(2022)1 cited
• Photocatalytic Degradation of Rhodamine B Solution by ZnO Film(2013)