The dissolution reaction of Nd(III) trihydroxide solid phase was quantitatively investigated in the pH c range of 6.8 to 8.0

at 0.1 M NaCl medium under carbonate-free condition. Prior to the solubility experiment, the solid phase characterization

was conducted on the starting material using various analytical methods such as XRD, TA-DTG, and SEM/TEM, to obtain

stoichiometric information about the synthesized Nd(III) solid phase. For the solubility experiment, the Nd(III) solid phase

was equilibrated by means of the undersaturation approach, and the concentrations of aqueous Nd(III) species were quantifi ed

using UV–Vis absorption spectroscopy coupled with the liquid waveguide capillary fl ow cell (LWCC) and ICP-MS/OES.

After fi ltering the aqueous solution through both syringe and membrane fi lters, the measured aqueous Nd(III) concentration

indicated that no or trivial contribution from the colloidal phase of Nd(III) during the solubility experiment. Based on

chemical thermodynamic calculations using experimental results and literature data, the solubility product constant of Nd(III)

trihydroxide solid phase was determined to be log * K 0

s,0 = 18.14 ± 0.53 at infi nite dilution by applying the SIT approach ( i.e. ,

I = 0). This study demonstrated that UV–Vis absorption spectroscopy coupled with LWCC can be eff ectively employed for

the quantitative analysis of aqueous lanthanide ions at low concentrations, even without the need for additional complexing

agents.