Detection of polynuclear zirconium hydroxide species in aqueous solution by ESI-MS

The direct detection of polymerized tetravalent zirconium hydroxides was performed by using a commercially available desktop electrospray ionization mass spectrometry equipped with a nanospray capillary heated at 90℃. It was confirmed that the abundance ratio of the species did not depend significantly on the desolvation line temperature up to 170℃. In the acidic pH condition, the positively charged polymers up to 12-mer species of zirconium were assigned based on the m/z values and the natural abundance isotopic compositions of Zr and Cl. The distribution of the species was observed to change depending on the pH value and the aging period. The hydrolysis constants for the polynuclear species predominantly formed in solution were estimated from the analysis of the observed spectra with the help of an electrostatic hard sphere model. The obtained values were found to be comparable with the literature ones. (author)