LC-HRMS suspect screening for detection-based prioritization of iodinated contrast media photodegradates in surface waters.

The objective of the study was to demonstrate the applicability of suspect screening for the detection of six iodinated contrast media (ICM) and their phototransformation products (TPs) in surface waters. First, a photodegradation study of ICM in surface water using a sunlight lab-scale simulator was performed. By means of a guided differential sample analysis, the exact masses of the molecular ions and the retention times of TPs were identified. Positive findings were filtered manually generating a suspect list of 108 photoproducts. Following a generic solid-phase extraction of surface water samples, LC-HRMS was used to screen for the presence of the compounds previously detected in the photodegradation samples. On the basis of detection frequencies (>50% of the samples), 11 TPs were prioritized and their structures elucidated by HRMS and NMR. In the real surface water samples, median concentration of parent compounds was 110 ng/L reaching up to 6 μg/L for iomeprol, while TPs were found at median concentration of 8 ng/L, reaching up to 0.4 μg/L for iomeprol TP651-B. In summary, the proposed screening approach facilitates the evaluation of the degradation of polar compounds at a real scale with a fast detection of TPs without prior availability of the standards.