Identification of complexes involving toxic heavy metals with amino acid ligands by electrospray ionization mass spectrometry
Electrospray ionization mass spectra (ESI-MS) of reaction mixtures containing ions of the heavy metals, cadmium, mercury, thallium, lead, and bismuth with each of the naturally occurring amino acids allows for definitive identification of monocationic complexes in the gas phase. Prominent m/z peaks are assigned to ions of the type [E(Am) xH]+ (x = 0, 1, 2), [E(Am)2 xH]+ (x = 0, 1, 2), [E2(Am) xH]+ (x = 1, 2, 3), and (or) [E2(Am)2 xH]+ (x = 1, 3, 5) for all amino acids studied (Am) with all metals studied (E = Cd, Hg, Tl, Pb) except bismuth, which shows complexes with only seven amino acids (Am = His, Thr, Met, Cys, Hcys, Asn, Gln). The results demonstrate the potential application of ESI-MS as a versatile and efficient approach to study toxic heavy metals in biological systems.Key words: heavy metals, amino acids, electrospray ionization mass spectrometry.