Fragmentation behavior of EDTA complexes under different activation conditions.

Ethylenediaminetetraacetic acid (EDTA) is an aminopolycarboxylic acid and complexation agent that is able to bind a large variety of metals. The formation of highly stable metal-EDTA complexes is generally very quick. This has led to the use of EDTA in a variety of applications, including food, medical, and household applications. In the current study, we have investigated the fragmentation behavior of EDTA and various metal complexes under collision-induced dissociation (CID), infrared-multiphoton dissociation (IRMPD), and higher-energy collisional dissociation (HCD) activation conditions. Both, positive and negative mode electrospray ionization (ESI) were applied. The metals used to complex with EDTA ranged from alkaline earth metals, such as sodium and cesium, via calcium, nickel, zinc, aluminum, copper, iron, and indium to yttrium and several lanthanides. Furthermore, the protonated and deprotonated species of EDTA, as well as disodium and trisodium species, have been subjected to fragmentation. The results show that characteristic fragmentations were obtained for EDTA and the metal complexes under the investigated conditions. The use of an ion cyclotron resonance (ICR) and an Orbitrap mass spectrometer, as high resolution-accurate mass instruments, allowed the assignment of elemental compositions undoubtedly for the vast majority of fragments. Certain trends were observed that trend correlated with the size of the metal and the location within the periodic table.