Table 3 Relative abundance of the released free Cu and Ni isotopes from Cu(II)/Ni(II)–NA complexes.

Relative abundance of ⁶³Cu released from ⁶³Cu(II)-NA, m/z 365 at different HCD
Cu(II)-NA std sol.	40	50	60	70	80	90
1x	0.025	0.268	0.426	3.531	4.912	9.818
dilution 1:2	0.021	0.209	0.256	1.567	3.406	5.945
dilution 1:4	0.010	0.099	0.328	0.925	2.053	3.751
dilution 1:6		0.087	0.225	0.690	1.390	2.417
dilution 1:8		0.056	0.191	0.518	1.027	1.937
dilution 1:10		0.054	0.148	0.439	0.860	1.443
Relative abundance of ⁶⁵Cu released from ⁶⁵Cu(II)-NA, m/z 367 at different HCD
Cu(II)-NA std sol.	40	50	60	70	80	90
1x	0.004	0.079	0.373	1.046	2.053	2.257
dilution 1:2		0.070	0.237	0.419	1.019	1.824
dilution 1:4		0.037	0.133	0.372	0.705	1.280
dilution 1:6		0.026	0.105	0.228	0.480	0.777
dilution 1:8		0.015	0.081	0.189	0.396	0.593
dilution 1:10		0.017	0.056	0.146	0.295	0.530
Relative abundance of ⁵⁸Ni released from ⁵⁸Ni(II)-NA, m/z 360 at different HCD
Ni(II)-NA std sol.	40	50	60	70	80	90
1x			0.009	0.044	0.156	0.254
dilution 1:2			0.004	0.046	0.114	0.248
dilution 1:4				0.048	0.111	0.207
dilution 1:6				0.034	0.103	0.176
dilution 1:8				0.028	0.080	0.174
dilution 1:10				0.021	0.062	0.135
Relative abundance of ⁶⁰Ni released from ⁶⁰Ni(II)-NA, m/z 362 at different HCD
Ni(II)-NA std sol.	40	50	60	70	80	90
1x				0.027	0.049	0.127
dilution 1:2				0.023	0.071	0.103
dilution 1:4				0.023	0.057	0.095
dilution 1:6				0.021	0.047	0.095
dilution 1:8				0.021	0.036	0.090
dilution 1:10				0.016	0.034	0.089

MS/MS data were obtained in positive ESI mode in Orbitrap-MS at different percentages of high-energy collisional dissociation (HCD: 40–90% shown in italics). The relative abundance of the released free metals was obtained by normalizing the peak intensity of the free metals, m/z 62.929 and 64.927 for ⁶³Cu and ⁶⁵Cu, respectively; m/z 57.935 and 59.930 for ⁵⁸Ni and ⁶⁰Ni, respectively, to that of the internal standard (leucine enkephalin, 2.0 ppm). Metal–NA standard complex solutions (std sol.) were prepared in distilled deionized water and further diluted up to 10-fold (dilution 1x to 1:10).

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