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The extraction of technetium, present in nitric acid medium as pertechnetate anion, is an issue in solvent extraction processes used to recover uranium and plutonium. In the present study, a complexing agent is added in the aqueous nitric acid solution to bind selectively the pertechnetate anion and prevent its extraction into the organic phase or to back extract it in the aqueous phase. Several azacryptands with the addition of hydrophilic groups were synthesized to improve the solubility of the previously studied cage molecule in nitric acid medium. Solvent extraction tests reveal that all the synthesized ligands have a similar complexation strength towards pertechnetate and are able to maintain this anion in the aqueous phase (0.5 M HNO3). These ligands are able to overcome the Hofmeister bias and selectively bind technetium in nitric acid solution. The azacryptand concentration can be increased by a factor of three in the liquid-liquid extraction conditions compared to our previous work. Coordination studies using microcalorimetry, Single Crystal X-Ray Diffraction (SC-XRD), infrared and Raman spectroscopies show the formation of an inclusion complex with hydrogen bonds stabilizing the oxo-anion within the cavity. This solubility improvement is promising for the introduction of this kind of macrocyclic azacryptands in a solvent extraction process.

In this work, we combined smartphone sensing with the indicator displacement approach for the determination of trans,trans-muconic acid (i.e.tt-MA), a benzene biomarker, in urine. Dicopper(II) azacryptate was employed as the receptor. The good match of tt-MA with the receptor cavity was suggested by DFT calculations, and confirmed experimentally by UV-vis titrations in buffered aqueous solutions. The binding constant was determined through fluorimetric titrations using the indicator displacement approach. This method also confirmed the high affinity of the azacryptate for tt-MA in artificial and spiked urine samples. A portable device was then obtained by adsorption of the chemosensing ensemble on silica gel using ELISA-like plastic wells as the support. Indicator displacement was detected and quantified by exposing the microplate to a UV-lamp (366 nm) and recording the RGB values with a smartphone. A good correlation was found between the R index values and urinary tt-MA in the occupational concentration range.