Table III. MS detection and screening method for five major Se isotopes in Se compounds (0.1000-atomic mass unit range).
| Se Isotopes | 76 | 77 | 78 | 80 | 82 | Retention Time |
| min | ||||||
| Natural isotopic abundance | 9.37 | 7.63 | 23.77 | 49.61 | 8.73 | |
| [M+H] + m/z positive ion mode | ||||||
| Selenocysteine | 164.9163–165.0163 | 165.9171–166.0171 | 166.9145–167.0145 | 168.9137–169.0137 | 170.9139–171.0139 | 1.93 |
| Selenocystine | 332.8924–332.9924 | 333.8937–333.9937 | 334.8934–334.9934 | 336.883–336.9883 | 338.8904–338.9904 | 1.54 |
| Selenocystathionine | 266.9018–267.0018 | 267.9027–268.0027 | 268.9001–269.0001 | 270.9092–271.0092 | 272.9096–273.0096 | 1.87 |
| Selenohomocysteine | 179.9398–180.0398 | 180.9406–181.0406 | 181.938–182.038 | 183.9371–184.0371 | 185.9374–186.0374 | |
| Selenomethionine | 193.9055–194.0055 | 194.9063–195.0063 | 195.8837–195.9837 | 197.8828–197.9828 | 199.8731–199.9731 | 3.12 |
| Selenomethionine − NH3+ | 176.8468–176.9468 | 177.8402–177.9402 | 178.8958–178.9958 | 180.8356–180.9356 | 182.8401–182.9401 | 3.12 |
| Methylselenomethionine | 208.9789–209.0789 | 209.9798–210.0798 | 210.9772–211.0772 | 212.9763–213.0763 | 214.9766–215.0766 | |
| S-Adenosyl-l-homoselenocysteine | 429.0270–429.1270 | 430.0270–430.1270 | 431.0244–431.1244 | 433.0234–433.1234 | 435.0241–435.1241 | |
| Adenosylselenomethionine | 444.0505–444.1505 | 445.0505–445.1505 | 446.0479–446.1479 | 448.0469–448.1469 | 450.0476–450.1476 | |
| Methylselenocysteine | 179.9398–180.0398 | 180.9406–181.0406 | 181.938–182.038 | 183.9371–184.0371 | 185.9374–186.0374 | 2.14 |
| Methylselenocysteine − NH3+ | 162.9133–163.0133 | 163.9141–164.0141 | 164.9115–165.0115 | 166.9106–167.0106 | 168.9109–169.0109 | 2.14 |
| γGlutamylmethylselenocysteine | 308.9824–309.0824 | 309.9884–310.0884 | 310.9807–311.0807 | 312.9798–313.0798 | 314.9803–315.0803 | 2.42 |
| Selenobetaine | 165.9367–166.0367 | 166.9376–167.0376 | 167.9349–168.0349 | 169.9341–170.0341 | 171.9344–172.0344 | |
| Selenolanthionine | 252.9562–253.0562 | 253.9571–254.0571 | 254.9544–255.0544 | 256.9535–257.0535 | 258.9538–259.0539 | |
| Selenodiglutathione | 705.0009–705.1009 | 706.022–706.1022 | 706.9996–707.0996 | 708.9986–709.0986 | 710.991–711.0991 | |
| Selenocystamine | 244.8927–244.9927 | 245.8939–245.9939 | 246.8914–246.9914 | 248.8905–248.9905 | 250.8906–250.9906 | |
| Selenourea | 119.9061–120.0061 | 120.9068–121.0068 | 121.9042–122.0042 | 123.9034–124.0034 | 125.9036–126.0036 | |
| [M+H] − m/z negative ion mode | ||||||
| Selenite (HSeO31−) | 124.8534–124.9534 | 125.8541–125.9541 | 126.8515–126.9515 | 128.8507–128.9507 | 130.8510–130.9510 | 1.83 |
| Selenate (HSeO41−) | 141.1407–141.2407 | 142.1490–142.2490 | 143.0901–143.1901 | 145.0901–145.1901 | 147.0960–147.1960 | 1.85 |