Table 2 Estimations of calculated and observed m/z of metal–DMA/NA complexes and their released free metal.

From: Identification of metal species by ESI-MS/MS through release of free metals from the corresponding metal-ligand complexes

	Elemental composition		Complex identification			Complex isotopic signature				Released free metal
	[M]	[M + H]⁺	calculated m/z	observed m/z	range of Δppm	metal isotope	calculated isotopic m/z	calculated intensity, %	range of RIA error, %	free metal	calculated m/z	observed m/z	range of Δppm
Metal-DMA complexes
DMA	C₁₂H₂₀N₂O₇	C₁₂H₂₁N₂O₇
Fe(III)-DMA	Fe(III)-C₁₂H₁₇N₂O₇	Fe(III)-C₁₂H₁₈N₂O₇	358.0463	358.0464	0.0–2.0	⁵⁶Fe	358.0463	100.0		Fe	55.9349	55.9347	3.6–8.9
						⁵⁴Fe	356.0510	6.3	0.1–1.0		53.9396	53.9389	5.6–13.0
						⁵⁷Fe	359.0468	2.4	0.1–2.7		56.9354	56.9420	n.a.
Cu(II)-DMA	Cu(II)-C₁₂H₁₈N₂O₇	Cu(II)-C₁₂H₁₉N₂O₇	366.0488	366.0480	0.5–2.3	⁶³Cu	366.0488	100.0		Cu	62.9296	62.9294	1.6–9.5
						⁶⁵Cu	368.0470	44.6	0.6–2.7		64.9278	64.9274	1.5–7.7
Ni(II)-DMA	Ni(II)-C₁₂H₁₈N₂O₇	Ni(II)-C₁₂H₁₉N₂O₇	361.0546	361.0548	0.3–3.0	⁵⁸Ni	361.0546	100.0		Ni	57.9353	57.9352	1.7–6.9
						⁶⁰Ni	363.0500	38.2	0.1–2.3		59.9308	59.9304	3.3–11.7
Zn(II)-DMA	Zn(II)-C₁₂H₁₈N₂O₇	Zn(II)-C₁₂H₁₉N₂O₇	367.0484	367.0494	1.4–4.9	⁶⁴Zn	367.0484	100.0		Zn	63.9291	63.9290	1.6–9.4
						⁶⁶Zn	369.0453	57.4	1.1–5.0		65.9260	62.9259	1.5–13.7
						⁶⁸Zn	371.0441	38.7	2.3–9.6		67.9248	67.9245	4.4–10.3
Co(II)-DMA	Co(II)-C₁₂H₁₈N₂O₇	Co(II)-C₁₂H₁₉N₂O₇	362.0524	362.0528	1.1–4.4	⁵⁹Co	362.0524	100.0		Co	58.9332	58.9330	1.7–8.5
Metal-NA complexes
NA	C₁₂H₂₁N₃O₆	C₁₂H₂₂N₃O₆
Fe(III)-NA	Fe(III)-C₁₂H₁₈N₃O₆	Fe(III)-C₁₂H₁₉N₃O₆	357.0623	357.0622	0.3–3.9	⁵⁶Fe	357.0623	100.0		*Fe	55.9349	55.9345	3.6–8.9
						⁵⁴Fe	355.0670	6.3	0.7–8.8		53.9396	n.i.	n.i.
						⁵⁷Fe	358.0628	2.4	1.9–5.4		56.9354	n.i.	n.i.
Fe(II)-NA	Fe(II)-C₁₂H₁₉N₃O₆	Fe(II)-C₁₂H₂₀N₃O₆	358.0701	358.0702	0.3–3.4	⁵⁶Fe	358.0701	100.0		Fe	55.9349	55.9344	1.8–8.9
						⁵⁴Fe	356.0748	6.3	0.0–8.9		53.9396	53.9393	1.9–13.0
						⁵⁷Fe	359.0706	2.4	0.3–9.0		56.9354	56.9424	n.a.
Cu(II)-NA	Cu(II)-C₁₂H₁₉N₃O₆	Cu(II)-C₁₂H₂₀N₃O₆	365.0648	365.0652	0.8–3.8	⁶³Cu	365.0648	100.0		Cu	62.9296	62.9292	1.6–7.9
						⁶⁵Cu	367.0630	44.6	0.5–5.2		64.9278	64.9274	1.5–9.2
Ni(II)-NA	Ni(II)-C₁₂H₁₉N₃O₆	Ni(II)-C₁₂H₂₀N₃O₆	360.0706	360.0705	0.3–4.2	⁵⁸Ni	360.0706	100.0		Ni	57.9353	57.9350	1.7–6.9
						⁶⁰Ni	362.0660	38.2	0.7–3.8		59.9308	59.9306	3.3–11.7
Zn(II)-NA	Zn(II)-C₁₂H₁₉N₃O₆	Zn(II)-C₁₂H₂₀N₃O₆	366.0644	366.0656	1.6–4.6	⁶⁴Zn	366.0644	100.0		Zn	63.9291	63.9290	0.0–4.7
						⁶⁶Zn	368.0612	57.4	2.5–8.3		65.9260	62.9257	4.6–12.1
						⁶⁸Zn	370.0601	38.7	1.1–9.2		67.9248	67.9246	2.9–10.3
Co(II)-NA	Co(II)-C₁₂H₁₉N₃O₆	Co(II)-C₁₂H₂₀N₃O₆	361.0684	361.0682	0.6–5.0	⁵⁹Co	361.0684	100.0		Co	58.9332	58.9328	1.7–8.5

Data were obtained in positive ESI mode with Orbitrap-MS. Mass accuracy of metal–DMA/NA complexes in MS1 and their released free metals in MS2 are quoted in parts per million (ppm, see Supplementary Tables S1 and S2), n=8. Isotopic mass accuracy was estimated with the calculated errors in relative isotopic abundance (RIA, see Supplementary Table S3), n=8. [M] and [M+H]⁺ indicate the neutral molecule and the protonated ions, respectively. Asterisk denotes Fe isotope released from Fe(III)–NA complex. n.a.-not accurate; n.i.-not identified.

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Table 2 Estimations of calculated and observed m/z of metal–DMA/NA complexes and their released free metal.

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