Investigation of the Interaction between 1-Hydroxyethane-1,1‘-diphosphonic Acid (HEDP) and Uranium(VI)

Abstract

A detailed study, using a panel of spectroscopic analytical methods, of the complexation between 1-hydroxyethane-1,1'-diphosphonic acid (HEDP) and uranyl ion (UO(2)(2+)) is reported. Results suggest that the metal complex is present as only 1:1 (metal/ligand) species at low concentration (<10(-)(4) M). The conditional constants of this complex were determined at various pH using time-resolved laser-induced fluorescence (TRLIF) and electrospray ionization mass spectrometry (ESI-MS). Further investigations indicate the presence of a 1:2 (metal/ligand) complex at higher concentrations ( approximately 10(-)(2) M). Selectivity studies as well as structural aspects are presented.

Ions generated from uranyl nitrate solutions by electrospray ionization (ESI) and detected with fourier transform ion-cyclotron resonance (FT-ICR) mass spectrometry

“…Samples for FT-ICR MS measurements were prepared by diluting the stock solution with methanol. Solutions from which positive ion spectra were acquired were 330 M in UO 2 2ϩ and 660 M in NO 3 Ϫ in a 66% CH 3 OH/33% H 2 O (vol/vol) solvent system; solutions from which negative ion spectra were acquired were 50 M in UO 2 2ϩ and 100 M in NO 3 Ϫ in a 95% CH 3 OH/5% H 2 O (vol/vol) solvent system.…”

“…In both cases, A can be OH, NO 3 , CH 3 O or a combination of these, although the formation of nitrate-containing species is clearly preferred (Table 1 for details).…”

“…In both experiments, the ion-molecule reaction times were the same as for m/z 301 (180 s) but the pressures were slightly different (2.4 ϫ 10 Ϫ8 torr for D 2 O and 4.8 ϫ 10 Ϫ8 torr for CD 3 OD). UO 2 ϩ reacts readily with CD 3 OD by adding three and four CD 3 4 ] ϩ in ion trap studies at higher partial pressures of water [17].…”

“…Alkali and transition-metal cations are known to form complexes with nitrate when an excess of NO 3 Ϫ is present in solution [42,43]. Generally, these complexes are of the form [(UO 2 )(NO 3 ) m ] Ϫ (m ϭ 1-3), although the formation of oxo-nitrate ([(UO 2 )(O)(NO 3 ) m ] Ϫ (m ϭ 1-2) and hydroxy-nitrate ([(UO 2 )(OH) n (NO 3 ) m ] Ϫ (n ϭ 1-2, m ϭ 0 -1) products are also observed [43].…”

“…One major difficulty is the paucity of methods that can be used to distinguish specific molecular species at low concentration in solution. Electrospray ionization mass spectrometry (ESI-MS) can provide molecular weight and structural information and has been used successfully for molecular characterization of U(VI) complexes with ligands of environmental or biological interest [1][2][3][4][5]. However, much fundamental work on the complex gas-phase chemistry of U(VI) and U(VI)-containing species remains to be done before ESI-MS can be used to characterize U(VI) species in natural waters.…”