Table 1. Fragment ions with C–C bond cleavage of TMS- and TBDMS-derivatized organic acids by EI.
| Metabolites | m/z | Number of organic acid-derived carbons | Carbon skeleton | Estimated chemical formula | Estimated cleavage group |
|---|---|---|---|---|---|
| TMS derivatization | |||||
| Citric acid (4TMS) | 273 | 5 | C1-2-3-4-5 | C11H21O4Si2 | TMS-COO and TMS-OH |
| Citric acid (4TMS) | 347 | 5 | C1-2-3-4-5 | C13H27O5Si3 | TMS-COO and CH3 |
| Citric acid (4TMS) | 363 | 5 | C1-2-3-4-5 | C14H31O5Si3 | TMS-COO |
| αKG (1MEOX, 2TMS) | 112 | 4 | C1-2-3-4 | C5H6NO2 | TMS-COO and TMS-O |
| αKG (1MEOX, 2TMS) | 156 | 4 | C2-3-4-5 | C6H10NO2Si | TMS-COO, CH3 and CH3O |
| αKG (1MEOX, 2TMS) | 186 | 4 | C1-2-3-4 | C7H12NO3Si | TMS-COO and CH3 |
| Succinic acid (2TMS) | 116 | 2 | C1-2 or C3-4 | C4H8O2Si | TMS-COO-CH2 |
| Fumaric acid (2TMS) | 115 | 2 | C1-2 or C3-4 | C4H7O2Si | TMS-COO-CH |
| Fumaric acid (2TMS) | 143 | 3 | C1-2-3 or C2-3-4 | C6H11O2Si | TMS-COO |
| Malic acid (3TMS) | 101 | 2 | C2-3 | C4H9OSi | TMS-COO, TMS-COO and CH3 |
| Malic acid (3TMS) | 117 | 1 | C4 | C4H9O2Si | Except TMS-COO |
| Malic acid (3TMS) | 189 | 2 | C2-3 | C7H17O2Si2 | TMS-COO, CH3 and CO |
| Malic acid (3TMS) | 233 | 3 | C2-3-4 | C9H21O3Si2 | TMS-COO |
| Malic acid (3TMS) | 265 | 1 | C2 | C9H25O3Si3 | Unknown |
| Malic acid (3TMS) | 307 | 3 | C2-3-4 | C11H27O4Si3 | CO and CH3 |
| TBDMS derivatization | |||||
| Citric acid (4TBDMS) | 431 | 5 | C1-2-3-4-5 | C19H39O5Si3 | TBDMS-OH, TB and CO |
| Citric acid (4TBDMS) | 357 | 5 | C1-2-3-4-5 | C17H33O4Si2 | TBDMS-OH and TBDMS-CO |
| Citric acid (4TBDMS) | 299 | 5 | C1-2-3-4-5 | C13H23O4Si2 | TBDMS-OH, TBDMS-CO and TB |
| αKG (1MEOX, 2TBDMS) | 156 | 4 | C2-3-4-5 | C6H10NO2Si | TBDMS-CO, TB and CH3O |
| αKG (1MEOX, 2TBDMS) | 186 | 4 | C1-2-3-4 | C7H12NO3Si | TBDMS-COO and CH3 |
| Malic acid (3TBDMS) | 217 | 2 | C2-3 | C9H21O2Si2 | TBDMS-COO, CO, TB and CH3 |
| Malic acid (3TBDMS) | 317 | 3 | C2-3-4 | C15H33O3Si2 | TBDMS-CO |
| Malic acid (3TBDMS) | 349 | 1 | C2 | C15H37O3Si3 | Unknown |
| Malic acid (3TBDMS) | 391 | 3 | C2-3-4 | C17H39O4Si3 | TB and CO |