Quantitative Sampling of Iodinated X-ray Contrast Media in Water by Diffusive Gradients in Thin-Films Technique

Iodinated X-ray contrast media (ICM) have emerged persistent contaminants due to their high polarity, persistence and biological inertness. In this work, a sampling method for monitoring the time-integrated concentrations of the six ICMs including iohexol, iopamidol, iomeprol, iopromide, iodixanol and ioversol in sewage effluents have been developed, using diffusive gradients in thin films (DGT) technique based on graphene nanosheets gel as the binding layer and commercial polyethersulfone membrane as the diffusion layer (G-DGT). The uptakes of the G-DGT for the six ICMs were evaluated in the synthetic solution, and found to be independent of pH range of 4–9, ionic strength range from 1×10⁻4 to 0.1 mol L⁻¹, and dissolved fulvic acid and tannic acid ranging from 0 to 20 mg L⁻¹. In the three spiked freshwater samples, the good precision and good agreement between CDGT and CSOLN confirm that the G-DGT is capable of accurate measurements of the six ICMs in freshwater. The time-integrated concentrations of ioversol and iopamidol can be detected with better reproducibility with respective to grab sampling due to the use in clinical practice. These illustrate that the G-DGT is an effective sampling tool for obtaining the time-integrated concentrations of ICMs in complex sewage effluent.