Preliminary speciation study of Co(II)-citrate system by ion pairing-reversed phase chromatography coupled to UV detector

Abstract

This paper describes the ability of ion pairingreversed phase chromatography coupled to UV detector to determine an experimental speciation of cobalt in the binary Co(II)-citrate system. A method has been developed to investigate aqueous Co(II)-citrate samples at physiological pH as a function of time, by varying metal-to-ligand ratios, concentration and temperature. Solid 1 : 1 dimeric and 1 : 2 monomeric Co(II)-citrate complexes previously described have been synthesised and their analysis by IP-RPC-UV allowed the assignation of the solution state separated species. In solution state and at Co(II) concentration of 5 × 10 −2 M, 1 : 2 Co(II)-citrate monomeric species are predominant forms, while 1 : 1 mono and dimeric complexes are the minor species. At Co(II) concentration lower than 5 mM, only species of 1 : 1 stoichiometry are involved in the aqueous cobalt distribution. The monitoring of the formed species as a function of time allows highlighting the high inertness of this system. At low concentration ranges, electrospray ionisation-mass spectrometry experiments were carried out to support the chromatographic data. This study is the first one establishing a link among synthetic cobalt-citrate complexes and species existing in solution.

Synthesis and Characterization of Novel Three-Dimensional Metallic Co Dendritic Superstructures by a Simple Hydrothermal Reduction Route

“…On the basis of the literature, , and the investigations described above, we believe that citrate plays two major roles in our system. On the one hand, citrate ions can coordinate with cobalt ions to form [Co(C 6 H 5 O 7 ) 2 ] 4− complexes in the excess of citrate solution, , which decreases the free Co 2+ concentration in solution and results in the slow generation of Co nanoparticles. Reaction velocity can be adjusted through the complexation slow-release method, which can regulate the kinetics of nucleation and growth of the products and further efficiently control the morphology and structure of the final products.…”

A Hydrothermal Reduction Route to Single‐Crystalline Hexagonal Cobalt Nanowires

“…[27] Citrate plays two major roles in our system. First, citrate ions can coordinate with cobalt ions to form [Co(C 6 H 5 O 7 ) 2 ] 4-complexes in the excess citrate solution, [28,29] which decreases the free Co 2+ concentration in solution and results in the slow generation of Co nanoparticles. The relatively slow reaction rate may be favorable for the subsequent growth of Co nanostructures along the easy magnetic axis of the hexagonal cobalt, namely the [001] direction.…”

Radionuclide speciation: A key point in the field of nuclear toxicology studies

“…This mode has also been used to elucidate cobalt-citrate species existing in solution at physiological pH (7.4) and 0.1 mM citric acid, reflecting biological conditions. 42 In a two-fold excess of citric acid, monomeric and dimeric species arise in solution. Moreover, ESI-MS is valuable to identify and characterise species in solution prior their analysis by separation techniques coupled to elemental detector, as in this latter case, separated species can be identified only on the basis of elemental information and retention times.…”