Rhodamine Sensors: Water Quality Monitoring

Why would I want to measure Rhodamine?

Fluorescent dyes like Rhodamine are often added to water systems to provide water discharge and velocity data. Dye tracing studies can provide useful information for modeling surface and groundwater systems in addition to tracing contaminants. Fluorometers allow researchers to measure ultra-low concentrations of dye.  The sensors extreme sensitivity and instrument flexibility allows researchers to glean powerful data that could potentially be missed when using less sensitive methods.

How is Rhodamine Measured?

Rhodamine WT is a highly fluorescent material with the unique ability to absorb green light and emit red light. Very few compounds have this property, so interferences from other substances are very rare. This makes Rhodamine WT a highly specific tracer. The fluorometer is configured to shine green light on the sample and detect the red light emitted. The amount of red light emitted is directly proportional to the concentration of the dye, up to 1000 parts per billion (1000 µg/L). Relative fluorescence readings, dye concentrations, dilution factors, dye travel time, and other parameters provide valuable data used to draw conclusions regarding the water system being studied.

What should I know about Rhodamine measurement in the field?

Dye tracers are compounds used for measuring, mapping, and monitoring water systems. Tracers are used for measuring water flows, studying and modeling surface and ground water systems, tracing contaminants in emergency response situations, detecting leaks, and measuring tank retention times. Fluorescent tracers like Rhodamine WT are chosen because they are cost-effective and easily and accurately measured on-site with a portable field-ready fluorometer, like the MantaPlus. This ideal tracer is nontoxic, usable in small quantities, cost-effective, easy to measure at very low concentrations, and stable during the course of the study. Rhodamine WT meets all of these requirements, and is approved for use by the Environmental Protection Agency.

Fouling can be a problem for fluorescence sensors.  Any foreign material that accumulates on the active surface of the sensor will either reduce the amount of emitted light or received light, or both.  And sometimes the foreign material might provide a false signal by fluorescing at the same wavelengths. Fouling typically does not pose a problem when profiling or spot checking for daily surveys; only when deployed for extended periods.  For continuous deployment, anti-fouling accessories may be added, such as Eureka’s universal wiper system, and copper mesh sensor guard.

Features of Solinst Eureka’s Rhodamine Sensors

Solinst Eureka’s MantaPlus multiparameter water quality probes may be configured to include any of our dye trace fluorometers. The Rhodamine sensor may be installed along with other sensors such as turbidity, dissolved oxygen, pH and conductivity.  This makes for a cost-effective approach, as there is no need to buy a dedicated fluorometer.  Operation is made easy, as the Rhodamine sensor is controlled by the Manta Control software, like other installed sensors.  If only the Rhodamine sensor is needed, it may also be installed stand-alone on one of Eureka’s smaller probes, such as the Trimeter.  The Trimeter with internal battery pack, for self-powered logging, is a popular configuration used for dye trace studies, both short and long term. 

Solinst Eureka’s Rhodamine fluorometer, installed in a Trimeter or MantaPlus multiprobe, provides an excellent tracer system.  Manta Plus and Trimeter Multiprobes may be configured as loggers with battery backs for autonomous self-powered deployment, used with field displays for site-to-site spot checking, or connected to data telemetry stations for real-time remote monitoring.  Eureka sondes equipped with fluorometers are portable, durable, and cost-effective. 

Fluorometers are available for common fluorescent dyes such as Rhodamine, Fluorescein, and PTSA, as well as for exotic and custom dye blends that may have unique properties that are beneficial to a specific environment or study.