Radiochemical purity

Technetium may exist in seven oxidation states. In the Tc eluate, the chemical species is Tc(VII)-pertechnetate. The Ph. Eur. states that not less than 95% of the radioactivity is identified as sodium pertechnetate [ Tc] by paper chromatography. 

---

Bromo-7-methyl-6-methylaminoquinoline was nitrated with ACONO2 to give the 6-N(N02)Me derivative, which rearranged in diluted sulfuric acid to the 5-nitro derivative. Reduction of the latter compound, followed by condensation with BrCN and final hydrogenolysis using H2, led to a product of >99% radiochemical purity (85MI1). 

Muelder and Shadoff (3) prepared C-2,3,7,8-Cl4-DBpD (0.9 mCi/ mmole) by chlorination of C-2,7-dichlorodibenzo-p-dioxin made from potassium C-2,4-dichlorophenate. The preparation of tritium-labeled 2,3,7,8-Cl4-DBpD is justified because the radiolabeled intermediates are less expensive and more accessible and because a higher specific activity is potentially attainable. Here, we consider the optimal conditions for the reaction sequence designed to obtain products of high chemical and radiochemical purity shown at the top of p. 8. 

Tc(V) gluconate and glucoheptonate are often used when the reaction should be carried out in a neutral aqueous- or mixed aqueous/organic medium, and a rapid exchange reaction and high radiochemical purity of the product is required. In radiopharmaceutical preparations, Tc(V) tartrate is also quite often used. For labelling modified antibodies Tc(V) tricine has recently been particularly recommended [33],... 

Cu labeling of TETA proceeded with high radiochemical purity... 

I] 214) 52% radiochemical yield after HPLC, specific activity 27 Ci mmol ( 100% radiochemical purity... 

Typical validation for radiochemical and radiopharmaceutical purity. Quality control is very important to ensure the safety and efficacy of radiopharmaceuticals. One important quality parameter is the radiochemical purity of the radiolabeled product. This is defined as the fraction of the total radioactivity in the desired chemical form in the radiopharmaceutical [56]. Radiochemical impurities come from incomplete labeling, shift of equilibrium, radiolysis ((3 decay), temperature or pH change, exposure to light,... 

Mah, G., Reilly, R. M., Wong, G. L. and Houle, S. A comparison of three methods to determine the radiochemical purity of 99mTc-hexamethylpropylene amine oxime (99mTc-HMPAO). Nucl. Med. Commun. 10 733-740,1989. 

The chemical and radiochemical purity of the labeled compound must be ascertained prior to use. In practice a value of 95% or greater is usually acceptable. The desired specific activity of the administered radioactive compound depends on the dose to be used as well as the species studied. Doses of 14C on the order of 5 pCi/kg for the dog and 20 pCi/kg for the rat have been found adequate in most studies, while doses of 3H are usually two to three times higher owing to lower counting efficiency of this isotope. 

Finally, radiopharmaceuticals are often prepared on a daily basis within the framework of clinical studies which often last several months or years. They demand a viable and reproducible production chain, leading to a sterile- and pyrogen-free radiopharmaceutical of high radiochemical purity. Therefore, microprocessor-controlled automated synthesis devices [31] are developed in order to ensure routine pharmaceutical production. They are becoming mandatory in order to meet the demands related to Good Laboratory Practice (GLP) and Good Manufacturing Practice (GMP). 

F. Fuchtner, P. Angelberger, H. Kvaternik, F. Hammerschmidt, B. Peric-Simovc, J. Steinbach, Aspects of 6-[ F]fluoro-L-DOPA preparation Precursor synthesis, preparative HPLC purification and determination of radiochemical purity, Nucl. Med. Biol. 29 (2002) 477-481. 

Radiochemical purity should be demonstrated by one or preferably two separate dilution analyses as described in Section 6b, or by degradation experiments together with dilution analysis. Neglect of this important... 

As an example the carrier addition method 2 is described in more detail in the appendix since this is important for establishing the radiochemical purity of labelled compounds. The other two procedures are similar in principle and are described elsewhere (29). The technique has been used to measure the products of initiator side reactions in azoiso-butyronitrile initiated polymerizations (30—33) and in benzoyl peroxide decomposition (34) and is capable of much wider application than it has so far received. 

Unfortunately this ingeneous mechanism remains speculative since there is some doubt as to the identity of some of the labelled compounds. Thus, Mufti and Poller were unable to repeat the preparation of dibutyl tin bis (methyl maleate) but obtained instead dibutylchlorotin methyl maleate (93). Also there was no clear indication of either the chemical purity or the radiochemical purity (see Section 5 c) of the compounds BuaSnY2 (94). 

A hypothetical illustration of the importance of radiochemical purity a postulated free radical copolymerization of benzene with a vinyl monomer ... 

---