Occurrence of triiodinated X-ray contrast agents in the aquatic environment.

High concentrations of adsorbable organic iodine (AOI) are found in municipal treatment plant effluents and surface waters by specific organic halogen determination. The high AOI is caused by widely used triiodinated X-ray contrast agents, which are very stable and hydrophilic. We have analysed specifically surface water influenced by a municipal treatment plant effluent, the surface water after bank filtration and raw drinking water. The X-ray contrast agents were determined by liquid chromatography-mass spectrometry with positive electrospray ionization after enrichment by solid phase extraction. Diatrizoate and iopromide, two triiodinated contrast agents are detectable in all samples, whereby the less polar component iopromide seems to be reduced during bank filtration. Just a trace of iopromide is identified in surface water after bank filtration and in the raw drinking water. Approximately 60% of the initial AOI is extractable and approximately 25% of the extractable AOI can be identified as specific triiodinated contrast agents.