Tetraphenylarsonium pertechnetate

Early in 1970, Few et al. [10] radiolabelled polystyrene particles for a mucociliaiy clearance study. The radiolabelled aerosols were produced by a spinning-disk generator. The technique involves the key steps of extracting sodium pertechnetate (Na " Tc04) into chloroform as tetraphenylarsonium pertechnetate, followed by evaporation of the chloroform. A solution of polystyrene is added to the radioactive residue and dispersed Scheme 1). This technique has subsequently been adopted by... 

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 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. 

Tc (a) Precipitation as tetraphenylarsonium pertechnetate. (b) Extraction as tetraphenylarsonium pertechnetate into CHCI3 and back-extraction with 0.2 M I4CIO4. 

A thermodynamic investigation of the solubility and extraction of tetraphenylarsonium pertechnetate, Ph4AsTc04, has been carried out in a large number of solvents. The standard free energies of transfer have been used to characterize the difference between the solubility in HjO and in organic solvents. The concentration dependence of the distribution coefficients is a function of the dissociation and association of Ph4AsTc04 in the two phases. 

Some precipitation methods have been applied to the separation of technetium from molybdenum when the former occurs as a radio-active daughter-product of the latter. The separation of technetium is performed by co-precipitation with tetraphenylarsonium perrhenate from an alkaline molybdate solution . In this way, also ruthenium remains in solution. Molybdate may be precipitated away from pertechnetate using 8-hydroxyquinoline " or a-benzoinoxim Pb or Ag" ions can also be used . Kuzina and Spitsyn have developed a method for concentrating technetium from ammoniacal molybdate solutions by co-precipitat-ing pertechnetate with the slightly soluble crystalline MgNH PO. ... 

Procedure To the sample which contains 20-300 /xg of pertechnetate in 5-20 ml of solution, are added potassium perchlorate solution (2 ml, 1 mg KCIO per ml) and enough NaCl to make the solution approximately 1 M. The solution is heated and neutralized with ammonia. Pertechnetate is precipitated with aqueous 5 % tetraphenylarsonium chloride reagent. The precipitate is filtered, washed and dried, and a 2-mg portion is mixed with potassium bromide (300 mg). The mixture is pressed to form a clear disc by the usual technique. The infrared spectrum is recorded between 10 and 12 /x. The peak absorption is measured at 11.09 /X by the base-line technique. 

The solution of (CgHj) AsTcO is passed through an ion exchange resin in the chloride form. Pertechnetate ions are strongly adsorbed while tetraphenylarsonium chloride is recovered in the runnings. Pertechnetate is then eluted from the resin by 2 N NaOH. Nitron pertechnetate is dissolved in ethyl acetate and the solution is shaken with dilute ammonia. TcO passes into the aqueous layer while the nitron remains in the ester . 

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). 

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