Electrochemical reduction of the iodinated contrast medium iomeprol: iodine mass balance and identification of transformation products.

Potentiostatic-controlled electrochemical reduction of iomeprol was used to deiodinate iomeprol (IMP), a representative of the iodinated X-ray contrast media. The reduction process was followed by product analysis with liquid chromatography-electrospray ionization-tandem mass spectrometry and ion chromatography-inductively coupled plasma-mass spectrometry. The identification is mainly based on the interpretation of the mass fragmentation. The product analysis showed a rather selective deiodination process with the successive occurrence of IMP-I, IMP-2I, IMP-3I, and a transformation product (TP), respectively. The TP was formed from IMP-3I by a further cleavage of an amide bond and release of a (C=O)CHOH group from the side chain of IMP. The iodine mass balance on the basis of IMP and iodide showed a gap of about 26% at the beginning of the electrolysis process which could be completely closed by taking the intermediates IMP-I and IMP-2I into consideration. This means that the major intermediates and the TPs were considered and that the reduction process is a rather selective one to remove organically bound iodine from X-ray contrast media. An attractive application area would be the electrochemical deiodination of X-ray contrast media in urine of patients or hospital effluents.