Table 4. Spectral Summary of PBNA and Nitro Derivatives Found in the ESI– and ESI + Modes.
| PBNA | PBNA-NO2 | PBNA-(NO2)2 | PBNA-(NO2)3 | PBNA-(NO2)4 | PBNA-(NO2)5 | ||||
|---|---|---|---|---|---|---|---|---|---|
| adduct type | [M + H]+ | [M – H]− | M + H]+ | [M – H]− | [M + H]+ | [M – H]− | [M + H]+ | [M – H]− | [M – H]− |
| TR (min, ± 0.015 min) | 6.420a | 6.062 | 6.086 | 6.034 | 6.057 | 6.212 | 6.233 | 6.048 | 5.701 |
| 6.557a | 6.434b | 6.463b | 5.938a | 5.763a | |||||
| 6.750a | 5.815a | 5.862a | |||||||
| MS1 mass (Da) | 220.1121 | 263.0826 | 265.0972 | 308.0676 | 310.0825 | 353.0527 | 355.0677 | 398.0375 | 443.0220 |
| MS1 ion RMS error (ppm) | ±1.02 | ±1.13 | ±0.54 | ±1.30 | ±1.11 | ±0.71 | ±1.13 | ±0.51 | ±0.71 |
| accurate mass of MS2 fragment ions (Da) | 143.0726 | 233.0847 | 248.0935 | 278.0699 | 293.0780 | 306.0511 | ND | 351.0372 | 380.0275 |
| 115.0545 | 216.0840 | 218.0964 | 277.0619 | 292.0707 | 290.0574 | 322.0465 | 367.0283 | ||
| 92.0494 | 261.0661 | 275.0694 | 277.0620 | 307.0477 | 352.0330 | ||||
| 248.0713 | 263.0812 | 262.0622 | 278.0572 | 351.0374 | |||||
| 231.0683 | 246.0792 | 233.0720 | 262.0584 | 350.0283 | |||||
| 220.0766 | 245.0722 | 217.0769 | 248.0586 | 277.0489 | |||||
| 192.0813 | 229.0748 | 205.0774 | 232.0628 | 260.0460 | |||||
| 45.9928 | 218.0844 | 191.0614 | 220.0638 | 236.0505 | |||||
| 217.0772 | 186.0312 | 186.0300 | |||||||
| 45.9932 | 45.9933 | ||||||||
ND, not detected.
Examples of mass spectra: Figures S3–S6, S9–S11, and S14.
a
Secondary or tertiary isomers due to their low intensities.
b
Secondary isomer with unusually high intensity in ESI+ but low intensity on ESI–.