Pertechnetate salts

Extraction with a 0.15 M solution of methyltricaprylammonium chloride in chloroform results in the quantitative isolation of pertcchnetate from aqueous media, ranging from 4M sulphuric acid or 9 M hydrochloric acid to pH 13. The formation of a 1 1 organic calion-pertechnetate salt appears to be requisite for the extraction at any pH ... 

Tetraphenylarsonium pertechnetate is precipitated in the presence of perchlorate as the carrier. The mixed salts are disolved in concentrated sulfuric acid and the solution is electrolyzed at platinum electrodes. The black deposit (TcOj) obtained is dissolved in perchloric acid, technetium heptoxide is distilled out of the solution... 

The dependence of the extraction coefficient of pertechnetate on the salt concentration and kind of anions being an aqueous solutions is shown in Fig. 5. 

Fig. 5. Extraction of pertechnetate from aqueous salt solutions with tri-n-butyl phosphate ...

Pertechnetate forms sparingly soluble salts with several large cations, e.g. 

The most popular method involves weighing of the precipitate in the form of tetraphenylarsonium pertechnetate . Precipitation is carried out from neutral or alkaline solution at pH 8-9 by adding an excess of tetraphenylarsonium chloride (CgH5) AsCl. Since the precipitated salt is slightly soluble the total volume of the solution is kept to a minimum. 

The vibrational spectra of pertechnetates have only lately been widely studied. Busey and Keller (86) have reported the original IR and Raman spectra of crystalline KTCO4. The measurements were later completed (85, 115). Additional salts have also been measured (107). All these data are collected in Table 13. The IR data for tetraphenylarsonium and tetraphenylphosphonium pertechnetate can be found in Ref. (115). The vi(A ) stretch in pertechnetates has been observed in the Raman effect and found to lie at 910 cm i for KTCO4 (84). 

Fission products Cesium (Cs), strontium (Sr), barium (Ba), and technetium (Tc) are main isotopes present as salts (nitrates and chlorides). Tc may be present as oxides All salts are soluble. Tc oxidizes as soluble pertechnetate, but in reduced state, it is less soluble... 

Zinc reduction of [TcClg] in HCl (aq) produces the mixed-valence dimer [TcaClg] ". The analogue of Ref[TciClg] , is isolated by workup of products from reduction of pertechnetate with hypophosphorus acid. The [n-Bu4N]2 [TC2CI8] is isolated and converted to [Tc2Br8] salts . 

Chemically, radioactive molybdate Mo04 converts to radioactive pertechnetate ion (TCO4 ). The radioactive Tc04 is removed from the generator when needed. It is administered to the patient as an aqueous salt solution that has an osmotic pressure identical to that of human blood. 

Effect of formulation. Kits contain very low amounts of stannous ion for reduction of Tc-pertechnetate nevertheless, SnCl2 is usually in high excess. There are several reasons for using stannous salt in excess. Stannous salts are spontaneously oxidized in air. Also, oxidant species in the eluate may have been formed by radiolysis the amount of Sn(II) available in solution is very low with respect to the total amount of lyophilized SnCl2. In order to assure validity of kits beyond the expiration date, an excess of SnCl2 is used in the kit formulation. 

Another aspect is hydrolysis and colloid formation. During the reduction of pertechnetate with stannous salts, tin is oxidized and hydrolyzed to form highly polydispersed colloidal particles. In some cases, mainly when weak or unsuitable ligands are used in the " Tc labeling, interference of colloidal tin oxides on the biodistribution of " Tc-radiolabeled tracers may occur. Such effects and the biodistribution of Tc-Sn colloid in dependence of the preparation conditions were subject of detailed studies. 

Trapping of reducing tin(II) salts (in colloidal form) in the pores of the column material has also been observed to affect radiochemical purity, because the pertechnetate content in the subsequent samples will be reduced, providing false values. 

Radiopharmaceutical kits for labeling with Tc eluate contain tin(II)-ion for reduction of sodium pertechnetate to lower valency states, which are chemically reactive. Tin(II) salts are easily oxidized, even by the oxygen in air. Certain chemicals are also assumed to enhance the oxidation of tin(II) to tin(IV). Therefore, determination of tin(II) in radiopharmaceutical kits is an important aspect of quality control. 

MPI To 99m Generator NeoTect Pertechnetic acid (H " Tc04), sodium salt Pertscan-99m Sodium pertechnetate (Na " Tc04) Sodium pertechnetate (Tc-99M) Sodium pertechnetate "Tc Sodium pertechnetate Tc 99m Ultra-Technekow FM. A radioactive agent. Used in brain scans, thyroid function tests. Abbott Labs Inc. 

In strongly acidic media, cupferron, the ammonium salt of N-nitroso-N-phenylhy-droxylamine, seems to form with TcOf adduct [(Cupf) (Tc04)"[ or an adduct with pertechnetic acid, which can be extracted from 6 M HCl into ether by 99 %. The occurrence of any significant reduction was not observed. Tc(IIl), prepared by coulometric reduction of pertechnetate, was extracted as a cupferrate into ether up to 26% [152],... 

---