. 2022 Mar 24;10:862007. doi: 10.3389/fchem.2022.862007

TABLE 1.

The peak assignments of arginine standard in TOF-SIMS spectra in the positive mode.

No	Observed mass (m/z)	Chemical formula	Deviation (ppm)	Species
required peaks
1	175.1398	C₆H₁₅N₄O₂ ⁺	119.2	[M + H]⁺
characteristic peaks
2	160.1095	C₆H₁₄N₃O₂ ⁺	9.0	[M-(NH)+H]⁺
3	158.0880	C₆H₁₂N₃O₂ ⁺	−28.0	[M-(NH₃)+H]⁺
4	129.1212	C₅H₁₃N₄ ⁺	59.6	[M-(COOH)]⁺
5	114.1047	C₅H₁₂N₃ ⁺	18.7	[M-(NH₂)-(COOH)+H]⁺
6	112.0863	C₅H₁₀N₃ ⁺	−5.5	[M-(NH₃)-(COOH)]⁺
7	100.0874	C₄H₁₀N₃ ⁺	5.1	[M-(CH₃N)-(COOH)]⁺
8	87.0848	C₃H₉N₃ ⁺	65.6	[M-(C₃H₆NO₂)+H]⁺
9	73.0650	C₂H₇N₃ ⁺	20.6	[M-(C₄H₈NO₂)+H]⁺
10	60.0622	CH₆N₃ ⁺	108.8	[M-(C₅H₉NO₂)+H]⁺
other peaks
11	72.0818	C₄H₁₀N⁺	14.2	—
12	70.0719	C₄H₈N⁺	96.1	—
13	59.0513	C₃H₇O⁺	37.0	—
14	44.0490	C₂H₆N⁺	-10.8	—
15	42.0353	C₂H₄N⁺	35.4	—
16	41.0394	C₃H₅ ⁺	19.6	—
17	30.0371	CH₄N⁺	109.1	—
18	28.0201	CH₂N⁺	68.7	—
19	18.0363	NH₄ ⁺	136.0	—