Because a compound's MS spectrum is a very reliable and reproducible 'fingerprint', we can instruct the instrument to search an MS database and identify each compound in the sample. 0000015263 00000 n Abnormal results may be caused by disorders such as Graves' disease or Hashimoto's thyroiditis. Mentions of radioiodine in health care contexts refer more often to iodine-131 than to other isotopes. <> 0000039115 00000 n 0000010793 00000 n 0000012837 00000 n Iodine is more difficult to detect because it is one of the few compounds that is monoisotopic. One important subfield of proteomics is the search for protein 'biomarkers' for human disease: in other words, proteins which are present in greater quantities in the tissues of a sick person than in a healthy person. (. %������������ Its modes of decay are: 74.4% electron capture, 25.6% positron emission. In the mass analyzer component, the positively charged fragments and any remaining unfragmented molecular ions are accelerated down a tube by an electric field. The sample is acetone. Modern protein MS is extremely sensitive – recently, scientists were even able to detect the presence of Tyrannosaurus rex protein in a fossilized skeleton! endobj For example, a small peak one mass unit higher than a prominent peak is observed in mass spectra or organic molecules. 358 0 obj <>stream The process of buildup of xenon-135 from accumulated iodine-135 can temporarily preclude a shut-down reactor from restarting. 0000011671 00000 n 1. 0000191115 00000 n The beta particles emitted by the radioisotope destroys the associated thyroid tissue with little damage to surrounding tissues (more than 2.0 mm from the tissues absorbing the iodine). 0000191810 00000 n 0000014357 00000 n Most medical imaging with iodine is done with a standard gamma camera. Both 123I and 125I emit copious low energy Auger electrons after their decay, but these do not cause serious damage (double-stranded DNA breaks) in cells, unless the nuclide is incorporated into a medication that accumulates in the nucleus, or into DNA (this is never the case is clinical medicine, but it has been seen in experimental animal models).[6]. After the parent peak and the base peak, the next largest peak, at a relative abundance of 23%, is at m/z = 15. 0000002990 00000 n Its longest-lived radioactive isotope, 129I, has a half-life of 15.7 million years, which is far too short for it to exist as a primordial nuclide. endstream endobj 223 0 obj <>/Border[0 0 0]/C[1 0 0]/Dest(ninst.2)/F 4/H/I/Rect[155.295 627.519 161.076 634.524]/Subtype/Link/Type/Annot>> endobj 224 0 obj <>/Subtype/Form/Type/XObject>>stream endstream endobj 217 0 obj <> endobj 218 0 obj <>/Font<>>>/Fields[]>> endobj 219 0 obj <> endobj 220 0 obj <> endobj 221 0 obj <>/AP<>/Border[0 0 0]/C[0 1 1]/F 4/H/I/Rect[514.728 733.224 545.718 764.214]/Subtype/Link/Type/Annot>> endobj 222 0 obj <>/Subtype/Form/Type/XObject>>stream 0000012400 00000 n Current ICP-MS instrumental software corrects for all known atomic “isobaric” inter-ferences, or those caused by over-lapping isotopes of different elements, but does not correct for most polyatomic interferences. However, some isotopes are so prominent that they can easily be observed with a quadrupole mass spectrometer with unit resolution. There are 37 known isotopes of iodine (53I) from 108I to 144I; all undergo radioactive decay except 127I, which is stable. 0000034637 00000 n For 2-Propanethiol, Figure 6.5C contains a larger than usual [M + 2] peak, a pattern observable in sulfur containing compounds. 129I-enriched iodate is applied as a spike compound for the isotope dilution step. This is known as xenon poisoning or "falling into an iodine pit". xref 0000006702 00000 n 5. 0000015644 00000 n 0000009342 00000 n Exercise 4.2: Predict some signals that you would expect to see in a mass spectrum of 2-chloropropane. r�e�|3�݁����g�*v �?b�Յi0�� (f[��}�\��@Hf�@��Zu��$)�a�;�ϒ���4�giPX�\��i)���ɤyb�OnU0 ���#�����MmP��)tL3�g�ڹo�ͺo05��ݡ�s R��Jzw������e䘆@ؘ/�x� 12�8�QOc� /�'���qF�R���q:��uq���a��y^^8)J(�цQ�"L������>� ��>�P��{�3���DaQ^��(b2�%y�,��$pK/�ɝ��}��ؗ�j����!�Ǭ9o�3&P+�26 As a result, molecules containing different isotopes can be distinguished. There are some situations in which iodine-124 and iodine-125 are used in medicine, also.[3].