Table 1. MS/MS transitions and retention times. The table presents the MS/MS transitions for all the NTs examined in this study, and for the internal standards of the six small NTs. Isotope-labelled internal standards for the neuropeptides were not available at the time the study was conducted. Retention times are also included.
| Analyte | Internal standard | ||||
|---|---|---|---|---|---|
| Neurotransmitter | Precursor ion (m/z) | Product ion (m/z) | Precursor ion (m/z) | Product ion (m/z) | Retention time (min) |
| GABA | 104.07 | 87.0443 | 106.09 | 89.0569 | 6.9 |
| PEA | 122.10 | 105.0699 | 127.13 | 110.1012 | 4.0 |
| Dopamine | 154.09 | 137.0593 | 158.11 | 141.0843 | 6.2 |
| Serotonin | 177.09 | 160.0751 | 181.13 | 164.1003 | 4.8 |
| Adrenaline | 184.10 | 166.0856 | 190.13 | 172.1233 | 6.7 |
| Tryptophan | 205.10 | 188.0699 | 208.12 | 191.0887 | 4.7 |
| Oxytocin | 1007.40 | 723.26 | - | - | 5.4 |
| Vasopressin | 1084.45 | * | - | - | 8.4 |
*No considerable fragmentation for vasopressin was observed with fragmentation energy of 25 or 35%, so the precursor ion m/z (1084.455) was used for identification.