PTSA Fluorescence Sensors: Water Quality Monitoring

Why would I want to measure PTSA?

Fluorescent dyes, particularly those which are non-toxic and not visible, like PTSA, 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. With this extreme sensitivity and instrument flexibility, researchers can glean powerful data that could potentially be missed when using less sensitive methods.

PTSA dye is non-toxic and chemically stable, all of which make it an ideal trace additive for water treatment systems and agricultural applications. When adding PTSA to treatment formulations, the fluorescent response of the PTSA tracer dye is proportional and graphically linear, between specific concentration ranges, to the concentration of the chemical with which the system is dosed.  PTSA concentration, can be directly measured using a PTSA sensor installed in a MantaPlus or Trimeter multiprobe. Measurements from the PTSA fluorometer may be made available online, in the field and in the laboratory, to be expedited quickly and routinely, enabling real time product dose analysis. This allows improved accuracy of feed rate monitoring, continuous system monitoring, and control of system characteristics all ensuring that companies can improve their results and meet challenging system requirements.

How is PTSA Measured?

Solinst Eureka’s PTSA sensor is a fluorometric sensor.  Fluorescence occurs when a molecule absorbs light energy at one wavelength and then emits that energy at a different wavelength.  Fluorometric sensors emit light at a certain wavelength, and look for a very specific, different wavelength in return.

PTSA concentration, can be directly measured using a PTSA fluorometer sensor installed on a MantaPlus or Trimeter multiprobe.   This UV optical sensor detects the fluorescence of PTSA in water, up to 650 ppb. PTSA dye emits wavelengths between 400 and 500 nm when irradiated with UV light.

What should I know about PTSA measurement in the field?

PTSA is safe to handle, easy to dilute (specific gravity is 1.0), non-toxic or flammable, not reactive with other compounds, and non-hazardous waste, as defined by the Resource Conservation and Recovery Act (RCRA) 40 CFR 261. PTSA is also an ideal lab standard that can be used to standardize fluorometers configured for detection of CDOM/FDOM, Crude Oil, Optical Brighteners, and PTSA. PTSA can be used to standardize all of Eureka’s UV optical sensors or fluorometers. Also, customers who want to compare standardized UV sensors across multiple applications, either from the same or different manufacturer, can use PTSA so that values are reported as a standard unit of measure, making it easier to compare instrumentation deployed at long distances from each other.

Dye tracers like PTSA are 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 PTSA are chosen because they are cost-effective, and easily and accurately measured on-site with a portable field-ready probe like the MantaPlus.

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 Solinst Eureka’s universal wiper system, and copper mesh sensor guard.