Table 2. Most abundant isotope of the repeating unit for the brominated flame retardant in PBT computed by three different methods and examples of accurate mass measurements with assignment of the sum of the masses of the end-groups for the first congener.
| R (most abundant isotope) | Assignment | Error (ppm) | |
|---|---|---|---|
| Mass difference between consecutive oligomers (maxima of isotopic pattern) | 599.7799 | 599.77934 ↓ C18H16O3Br4* |
+0.9 |
| Single rotation of Kendrick plot | 599.7800* or ** | +1.1 | |
| Double rotation of Kendrick plot | 599.8020** | +37.8 | |
| Example of accurate measurement, 1-mer | Assignment | Error (ppm) | |
| m/z measured | m/z theoretical* | ||
| 1270.5858 | 1270.5826 | C39H36Br8O7Na+ ↓ C18H16O3Br4+C21H20O4Br4+Na+ (H, O, C and Br isotopes) |
2.5 |
| N.D. | 1271.5860 | N.D. | |
| 1272.5777 | 1272.5806 | −2.3 | |
| 1273.5763 | 1273.5839 | −6.0 | |
| 1274.5753 | 1274.5787 | −2.7 | |
| 1275.5788 | 1275.5820 | −2.5 | |
| 1276.5744 | 1276.5769 | −1.9 | |
| 1277.5746 | 1277.5800 | −4.2 | |
| 1278.5710 | 1278.5751 | −3.2 | |
| 1279.5762 | 1279.5780 | −1.5 | |
| 1280.5692 | 1280.5734 | −3.3 | |
| 1281.5709 | 1281.5762 | −4.1 | |
| 1282.5690 | 1282.5719 | −2.3 | |
| 1283.5715 | 1283.5744 | −2.2 | |
| 1284.5661 | 1284.5707 | −3.6 | |
| 1285.5694 | 1285.5728 | −2.6 | |
| 1286.5607 | 1286.5706 | −7.7 | |
*using Mass Mountaineer, **using Kendo, first and thirteenth horizontal alignments