X-Ray Photoelectron Spectroscopy of EDTA

Abstract The binding energies of N(1s) in ethylenediaminetetraacetic acid (EDTA) and its related compounds were measured by means of a photoelectron spectrometer, and the molecular structures of EDTA were discussed. Two kinds of peaks were observed in the N(1s) spectra of EDTA and its related compounds, with binding energies of about 401 and 399 eV. In EDTA-4H, the heights of the two peaks were almost equal, while in its sodium salts the peak height with the higher binding energy decreased as the number of carboxylate groups in the molecule increased. In EDTA-4Na, only a single peak with a low binding energy was observed. In EDTP-4H and GEDTA-4H, the spectra showed two peaks with different heights. The binding energy values of the main peaks of simple amino acids, such as glycine and alanine, were about 401 eV. From the above results, it can be deduced that there are two kinds of N atoms, =N+H– and =N– types, in an EDTA molecule.