Stability constants determination of successive metal complexes by hyphenated CE‐ICPMS

Abstract

The study of radionuclides speciation requires accurate evaluation of stability constants, which can be achieved by CE-ICPMS. We have previously described a method for 1:1 metal complexes stability constants determination. In this paper, we present its extension to the case of successive complexations and its application to uranyl-oxalate and lanthanum-oxalate systems. Several significant steps are discussed: analytical conditions choice, mathematical treatment by non-linear regression, ligand concentration and ionic strength corrections. The following values were obtained: at infinite dilution, log(beta(1) degrees (UO(2)Oxa))=6.93+/-0.05, log(beta(2) degrees (UO(2)(Oxa)(2) (2-)))=11.92+/-0.43 and log(beta(3) degrees (UO(2)(Oxa)(3) (4-)))=15.11+/-0.12; log(beta(1) degrees (LaOxa(+)))=5.90+/-0.07, log(beta(2) degrees (La(Oxa)(2) (-)))=9.18+/-0.19 and log(beta(3) degrees (La(Oxa)(3) (3-)))=9.81+/-0.33. These values are in good agreement with the literature data, even though we suggest the existence of a new lanthanum-oxalate complex: La(Oxa)(3) (3-). This study confirms the suitability of CE-ICPMS for complexation studies.

Formation of MSeO4(aq) complexes (M2+ = Mg2+, Co2+, Ni2+, Cu2+, Cd2+) studied as a function of temperature by affinity capillary electrophoresis

“…In the past few years, ACE has been widely used (i) to investigate chemical equilibria and measure stability constants of inorganic species and (ii) to determine the stable form of aqueous species [15,[17][18][19][20][21][22][23][24][25]. Models describing the formation of 1:1 complexes are often used [25][26][27] as well as models describing the formation of successive complexes using nonlinear regressions [15,17,19,21]. Moreover, commercial CE instruments perform measurements at a 5-60ЊC temperature range enabling to determine thermodynamic parameters such as entropy and enthalpy of reactions [25].…”

Atomic spectrometry update. Elemental speciation

“…Petit et al 125 have extended their work, reported last year, on the determination of stability constants of 1 : 1 metal-ligand complexes to successive complexation reactions for the uranyland lanthanum-oxalate systems. They report evidence for a new La-oxalate complex: La(Ox) 3 3À .…”

Recent advances in the combination of capillary electrophoresis with mass spectrometry: From element to single‐cell analysis

“…Their CE–ICP–MS system consists of a CEi‐SP20 CE–Interface (Reeko Instrument Co., Xiamen, China) and an Agilent 7500ce ICP–MS (Agilent Technologies). Stability constants of radionuclide complexes were accurately evaluated for the speciation analyses .…”