Simultaneous speciation of iodine-, gadolinium-, and platinum-based pharmaceuticals by HILIC-ICP-MS and its application to wastewaters

The presence of contaminants in drinking water resources is a topic of great interest, yet certain types of compounds as pharmaceutical residues are still under-documented. These contaminants include organometallic or halogenated complexes such as cancerostatic platinum compounds (CPC), gadolinium-based contrast agents (GBCA) and iodine contrast media (ICM). Because of their increasing use in recent years, their concentrations in effluents and surface waters can now reach μg L^-1 for iodine compounds and ng L^-1 for platinum- or gadolinium-based compounds. This work aims to develop an analytical methodology for the simultaneous speciation of iodine-, platinum- and gadolinium-based complexes at ultratrace levels (∼ng L^-1). Our developments focused on hydrophilic interaction chromatography (HILIC) coupled with ICP-MS to separate and quantify ten drug residues, including three iodine-, three platinum- and four gadolinium-complexes. Three HILIC stationary phases (two zwitterionic, i.e. phosphorylcholine and ammonium-sulfonic acid phases, and one silica charged phase) were compared under different mobile phase compositions (organic solvent percentage, salt concentration and pH). Dipole moment computations using density functional theory (DFT) were performed to refine our understanding of observed compounds complex separation in HILIC. Phosphorylcholine stationary phase with an acetonitrile gradient from 75 % to 50 % in 10 mmol L^-1 ammonium formate aqueous solution was found best compromise to achieve the separation of the ten tested complexes. Achieved LODs for the various complexes were between 1 and 3 ng L^-1 Gd, 3 and 17 ng L^-1 Pt and 46 and 63 ng L^-1 I. The developed method was applied to urban and hospital wastewaters. Two ICM (iohexol and iopamidol) and one GBCA (gadoterate) were quantified while no CPC were detected. Concentration of gadoterate was of the same order in the two types of wastewaters, i.e. between 525 and 677 ng L^-1 Gd. While iohexol was determined only in urban wastewaters at 30 μg L^-1 I, the concentration of iopamidol in urban wastewater was about 30 times lower than in hospital wastewater (134 ng L^-1 I).