Automated Water Sample Concentration: Optimizing Radionuclide and Heavy Metal Analysis Using Large-Scale Rotary Evaporation

Water is a critical source of hydration and serves as the primary medium for the intake of chemotoxic and radiotoxic substances. Given its significance, water quality is rigorously monitored, which demands significant efforts. Radionuclides and heavy metals are analyzed in various water sources, including surface water, drinking water, groundwater, wastewater, and rainwater, primarily as part of nuclear power plant monitoring. Continuous monitoring is conducted for β-emitters such as tritium, 14C, and 90Sr, as well as β-emitting isotopes of uranium, plutonium, americium, and curium, and γ-emitters like 137Cs and 60Co.

The detection limits for these substances often require concentration procedures, typically followed by radiochemical purification, to minimize interference across measurement techniques such as radiometry, mass spectrometry, and others. Radionuclide analysis is also carried out for research purposes, where the required detection limits are generally even stricter.

Evaporation is an effective method for concentrating radionuclides and heavy metals from large aqueous samples. Alternatively, sorbents or flocculating agents can be used, although these methods are less effective when analyzing samples containing chemically diverse radionuclides such as 137Cs, 90Sr, and plutonium isotopes.

Gentle concentration through evaporation in open vessels has traditionally been used, but it becomes time-consuming and impractical for larger sample volumes. For samples starting at around 10 liters, the use of large-scale rotary evaporators provides a more efficient solution. Additionally, distillation offers the advantage of simplifying the purification of tritium, which is found in aqueous samples as HTO (tritiated water). The distillate from a rotary evaporator can be directly used for activity measurement, such as through liquid scintillation counting for tritium analysis.

Conventional evaporators, however, require frequent manual refilling of the evaporation flask, leading to ongoing personnel involvement during normal working hours, which interrupts other tasks. Outside of operating hours, these evaporators must be shut down, significantly extending the evaporation process.