Tri carb 3180 tr sl

Stability constants for the coordination of Eu³⁺, Am³⁺, Cm³⁺, and Cf³⁺ were also achieved by monitoring the suppression of liquid–liquid partitioning of the radiotracer due to the increasing presence of an aqueous complexant. Aqueous solutions were prepared containing sub-millimolar amounts of ligand while maintaining p[H⁺] at 1.7, 1.8, 1.9, 2.0, and 2.1. Ionic strength was maintained at 2.00 M using sodium perchlorate. Aqueous complexation was balanced with the appropriate choice of HDEHP concentration in octane to allow accurate quantification of metal distribution. Non-aqueous phases were pre-equilibrated three times with 2.00 M NaClO₄ at the corresponding p[H⁺]. Preliminary time-dependent studies indicated the phase transfer equilibrium was attained for all measurements with H₄octapa and H₄pypa-peg (Figures S2 and S3 in the SI). For the mixtures traced with radioisotopes, the activity was measured using gamma spectroscopy (ORTEC GEM50P4 coaxial HPGe detector, DSPEC gamma spectrometer) for ¹⁵⁴Eu (123.07 keV), ²⁴³Am (74.66 keV), and ²⁴⁹Cf (388.17 keV) and liquid scintillation counting (Perkin Elmer Tri-Carb 3180 TR/SL) for ²⁴⁸Cm. The ratio of radioisotope activity in the organic and aqueous phases defined the liquid–liquid distribution.

For compounds I–IV, the chemical composition was determined on a sample of 50 mg each. The technetium in the compounds was determined by liquid scintillation on a Tri-Carb 3180 TR/SL instrument (PerkinElmer, Chiba, Japan), using a HiSafe 3 scintillator; the measurement error did not exceed 5%. C, N, O were determined using the EA 3000 EuroVector analyzer, the measurement error was not more than 10%. The halogens were determined by Mohr titration in the presence of potassium dichromate.

Desorption experiments were performed to investigate the stability of Sr sorbed from SW by Z4A. Firstly, Sr was sorbed on Z4A from artificial SW spiked with ⁸⁹Sr certified standard solution (100 kBq/g, relative uncertainty 0.7%, reference date: 19.8.2019.) provided by Czech Metrology Institute (Prague, CZ), using the solid-to-solution ratio of 5 g/L. After centrifugation, saturated Z4A solids were mixed either with 20 mL of deionized water (0.05 µS/cm) or with groundwater (Supplementary Table S3) from the location Šibice (Zaprešić, Croatia). Aliquots of supernatant were taken periodically for 60 days to follow ⁸⁹Sr desorption from Z4A. The activity of ⁸⁹Sr was measured by Cherenkov counting using liquid scintillation counter Tri-Carb 3180 TR/SL (PerkinElmer, USA).