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Mass fragments used to monitor caffeine, theobromine, theophylline, and ursolic acid in the ESI mode
| Compound | Mode | Mass fragments |
| Caffeine | Positive | 195.0 > 109.9 |
| Positive | 195.0 > 137.9 | |
| Theobromine | Positive | 181.0 > 138.0 |
| Positive | 181.0 > 163.0 | |
| Theophylline | Positive | 181.0 > 123.9 |
| Ursolic acid | Positive | 457.4 > 297.3 |
| Positive | 457.4 > 411.3 | |
| Positive | 457.4 > 439.3 | |
| Negative | 455.0 |
