Table 1. . Transitions and mass spectrometry parameters for all compounds and belonging internal standards.
| Compound | Precursor ion mass | Product ion mass | Cone voltage (V) | Collision energy (eV) |
|---|---|---|---|---|
| NAA | 123 | 78 | 25 | 16 |
| 80† | 25 | 16 | ||
| PIC | 123.9 | 78† | 30 | 16 |
| 96 | 30 | 16 | ||
| NA | 123.9 | 80† | 25 | 16 |
| 96 | 25 | 16 | ||
| 3-HA | 154 | 108† | 20 | 18 |
| 136 | 20 | 10 | ||
| QUIN | 168.1 | 78 | 20 | 18 |
| 124† | 0 | 10 | ||
| KYNA | 190.1 | 116 | 30 | 29 |
| 144‡ | 30 | 17 | ||
| TRP | 205.1 | 118 | 20 | 24 |
| 146† | 20 | 16 | ||
| L-KYN | 209.1 | 94† | 20 | 12 |
| 146 | 20 | 18 | ||
| XA | 206.1 | 160† | 25 | 16 |
| 188 | 25 | 10 | ||
| 3-HK | 225.2 | 110.1† | 14 | 16 |
| 162.1 | 14 | 16 | ||
| Internal standards | Precursor ion mass | Product ion mass | Cone voltage (V) | Collision energy (V) |
| NAA-13C6 | 129.1 | 101 | 20 | 16 |
| PIC-d4 | 128 | 82 | 4 | 17 |
| NA-13C6 | 130.1 | 57.1 | 32 | 16 |
| 3-HA-d3 | 157.0 | 83 | 24 | 24 |
| QUIN-d3 | 171 | 81 | 20 | 18 |
| KYNA-d5 | 195 | 121 | 28 | 26 |
| TRP-d3 | 208.1 | 118.8 | 40 | 26 |
| Kynurenine d4 | 213.2 | 94 | 30 | 15 |
| XA-d4 | 210.1 | 192 | 25 | 10 |
| 3-HK-d3 | 228.2 | 163 | 14 | 16 |
†
Quantifying ion.
‡
MS transition with the lowest response selected as quantifier ion.
3-HA: 3-Hydroxyanthranilic acid; 3-HK: 3-Hydroxykynurenine; KYNA: Kynurenic acid; L-KYN: L-Kynurenine; NA: Nicotinic acid; NAA: Nicotine amide; PIC: Picolinic acid; QUIN: Quinolinic acid; TRP: Tryptophan; XA: Xanthurenic acid.