P-emitters

Radon-222 [14859-67-7] Rn, is a naturally occuriing, iaert, radioactive gas formed from the decay of radium-226 [13982-63-3] Ra. Because Ra is a ubiquitous, water-soluble component of the earth s cmst, its daughter product, Rn, is found everywhere. A major health concern is radon s radioactive decay products. Radon has a half-life of 4 days, decayiag to polonium-218 [15422-74-9] Po, with the emission of an a particle. It is Po, an a-emitter having a half-life of 3 min, and polonium-214 [15735-67-8] Po, an a-emitter having a half-life of 1.6 x lO " s, that are of most concern. Polonium-218 decays to lead-214 [15067-28A] a p-emitter haviag = 27 min, which decays to bismuth-214 [14733-03-0], a p-emitter haviag... 

Elaborate precautions must be taken to prevent the entrance of Pu iato the worker s body by ingestion, inhalation, or entry through the skin, because all common Pu isotopes except for Pu ate a-emitters. Pu is a P-emitter, but it decays to Am, which emits both (X- and y-rays. Acute intake of Pu, from ingestion or a wound, thus mandates prompt and aggressive medical intervention to remove as much Pu as possible before it deposits in the body. Subcutaneous deposition of plutonium from a puncture wound has been effectively controlled by prompt surgical excision followed by prolonged intravenous chelation therapy with diethylenetriaminepentaacetate (Ca " —DTPA) (171). 

Chemical effects of nuclear decay have been studied in Germanium through the use of Ge and Ge. Ge decays to Ga with a 275 day half-life by 100% electron capture with no y quanta emitted. Ge is a P emitter which decays to As with a 11.3 h half-life, by three jS transitions having maximum energies of 710 keV (23%), 1379 keV (35%) and 2196 keV (42%). From this are calculated maximum recoil energies of 1.7 eV, 4.5 eV and 10.2 eV, respectively. 

C22-0050. The iron isotope with 33 neutrons is used in medical applications. It is a P emitter. A sample of iron containing 1.33 picograms (pico = 10 ) of this isotope registers 242 decays per second. 

What are the advantages of the radiochemical method compared with other in situ techniques It offers a direct relationship between surface radiation (N ) and surface concentration, which allows a direct measurement of the amount of adsorbed molecules on the electrode, a condition difficult to determine with other in situ techniques. The main limitation of the technique is the availability of radioactive forms of the compound the experimenter wants to study. In this respect, the type of radiation preferred is of the P-type, mainly because of the ease of detection and minimal safety hazards. Typical P-emitters used are H, C, S, Cl, and P, which as constituents of molecules, open a great variability of compounds for study. Figure 6.21 shows some experimental results obtained for the measurement of adsorption on single crystals using this radiochemical method. 

Tritium and 14C are p emitters— they give off electrons—having half-Hves of 12 and over 5000 years, respectively. Tritium is made on a large scale by neutron Irradiation of 6Li in a nuclear reactor. 

When designing a radiopharmaceutical one should have in mind the potential hazard the product may have to the patient. The goal must be to have maximum amounts of photons with a minimum radiation exposure of the patient. For use in therapy, P emitters and a emitters are particularly useful. For diagnostic purposes, y emitters are most widely used. In general, those y emitters with a short physical half-life and with a y energy between 100 and 300 keV are most widely used in medical application, since these can easily be detected by standard y cameras. 

Pure p emitters are not as easy to check as the y emitters. However, they may be checked for purity with a p spectrometer or a liquid scintillation counter. 

The relative advantages of using a p-emitter ( H and " C), rather than a y-emitter are ... 

Radiation hazards from P-emitters with low specific activity are minimal. 

Extraction and purification of the sample containing is not required as y-rays penetrate coloured solutions and soft tissue with negligible loss of energy. In the case of p-emitters, the scintillation solution must be colourless or quenching corrections must be applied. 

Besides gamma emitters of iodine and technetium and C radionuclides, representative of p-emitters, are often utilized in protein labeling. 

This element, being an active p emitter, receives little attention. A carbide (face-centered cubic) can be prepared but its stoichiometry is in doubt. A stoichiometry of TC23C6 can be predicted by analogy with trends in other systems. 

This process of radioactive decay is characterised by the product, the maximum energy of the emitted electron (3H 0.018 MeV) and the half-life of the isotope (3H 12.3 a). Other p emitters commonly used in biochemistry are ... 

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