Table I.
Comparison and summary for methods used to isotopically label stercobilin with 18O.
| Reaction Conditions | % 18O Label (STDEV) | |||||||
|---|---|---|---|---|---|---|---|---|
| 5% TFA (µL) |
H218O (µL) |
T (C °) | t (h) | Unlabeled m/z 595 |
118O m/z 597 |
218O m/z 599 |
318O m/z 601 |
418O m/z 603 |
| 1 | 5 | 50 | 4 | 10.6 (1.0) | 17.0 (3.1) | 25.0 (4.1) | 29.7 (1.5) | 17.7 (4.8) |
| 1 | 5 | 50 | 8 | 4.0 (0.9) | 10.0 (2.2) | 21.8 (0.9) | 35.4 (2.1) | 28.8 (2.0) |
| 1 | 5 | 60 | 4 | 2.4 (0.8) | 8.0 (1.5) | 19.7 (4.2) | 34.8 (6.8) | 35.2 (12.4) |
| 1 | 5 | 70 | 4 | 2.3 (0.5) | 8.4 (0.6) | 21.5 (1.6) | 39.3 (0.4) | 28.4 (2.3) |
| 1 | 10 | 60 | 4 | 6.2 (1.2) | 12.2 (1.3) | 28.2 (5.8) | 37.9 (2.7) | 16.0 (1.9) |
| 1 | 10 | 70 | 4 | 12.4 (7.5) | 24.2 (12.6) | 31.3 (3.7) | 23.8 (12.2) | 8.3 (6.3) |
| 1 | 10 | 70 | 8 | 2.3 (2.6) | 8.2 (4.2) | 20.6 (7.9) | 36.8 (2.0) | 32.7 (13.9) |