Table 2.

Assignment of mass ions observed in ESI-MS spectra (+ mode) for Pb(II)-cysteine solutions A, B and F (C_Pb(II) = 10 mM, H₂Cys/Pb(II) mole ratio 2.1, 3.0 and 10.0, respectively).^a

m/z (amu)	assignment	m/z (amu)	assignment
122.03	[H2Cys + H+]+	327.99	[Pb(H2Cys) – H+]+
144.01	[Na+ + H2Cys]+	349.97	[Na+ + Pb(H2Cys) – 2H+]+
165.99	[2Na+ + H2Cys – H+]+	449.00	[Pb(H2Cys)2 – H+]+
252.97	[Pb(HCOO)]+	451.99	[4Na+ + 3(H2Cys) – 3H+]+
294.00	[Pb(H2Cys) – H+ – H2S]+	594.99	[5Na+ + 4(H2Cys) – 4H+]+
308.99	[3Na+ + 2(H2Cys) – 2H+]+	635.97	[3Na+ + Pb(H2Cys)3 – 4H+]+
311.01	[PbC2H5N3O2]+	654.96	[Pb2(H2Cys)2 – 3H+]+
		676.95	[Na+ + Pb2(H2Cys)2 – 4H+]+

^aH₂Cys (C₃H₇NO₂S); m = 121.02