Technetium analysis

Ihsanullah. (1995). Significance and initial investigations for the separation of molybdenum from the anion exchange resin prior to technetium analysis by ICP-MS. J. Radioanal. Nucl. Chem. 191(1), 67. 

This book presents a unified treatment of the chemistry of the elements. At present 112 elements are known, though not all occur in nature of the 92 elements from hydrogen to uranium all except technetium and promethium are found on earth and technetium has been detected in some stars. To these elements a further 20 have been added by artificial nuclear syntheses in the laboratory. Why are there only 90 elements in nature Why do they have their observed abundances and why do their individual isotopes occur with the particular relative abundances observed Indeed, we must also ask to what extent these isotopic abundances commonly vary in nature, thus causing variability in atomic weights and possibly jeopardizing the classical means of determining chemical composition and structure by chemical analysis. 

Analysis of technetium is usually made after chemical separation of the element and it requires a chemical yield tracer (99mTc or 95mTc). These sometimes make... 

To transfer the original synthesis to technetium was not very convenient, as it would have to start from TcBr(CO)5 (32a). A preparation has recently been reported which starts from 3a or 19a in refluxing THF and used BH3 as the reducing agent [36]. The complex 31a could be isolated in 60-70% yield, based on Tc, and has been characterized by i.r. specroseopic methods as well as Tc and Cl analysis, and compared to its rhenium congener (Scheme 5). 

The specific features of the cluster compounds of technetium are such, that practically each new compound must be studied using single crystal X-ray structural analysis, because their complex structures do not allow the interpretation of the results from other physico-chemical methods of investigation. Therefore, the synthesis of single crystals suitable for X-ray structural analysis is the main and most laborious chemical task. 

Analysis of reactions (5-7) shows that there is a narrow range of HX and technetium ion concentrations in which there is a possibility of prolonging the existence of [Tc2X8]3- the limits of this range become markedly narrower in the order Cl > Br > I10. For example, at an initial concentration [Tc2C18]3 > 10 2 M and for 3 M < [HC1] < 6M, the solutions of the octachloroditechnetate can exist indefinitely without visible changes in the... 

Of special interest is the dehydration of polynuclear technetium bromide clusters, which contain hydroxonium cations with different numbers of hydration water molecules. Analysis of the results obtained leads us to conclude that at 140-200 °C dehydration occurs with a partial decomposition of the [H30(H20)3] + cations (30). 

Crystals of [Tc(tu)6]Cl3 or [TcCl(tu)5]Cl2 are often employed for the synthesis of technetium(III) complexes. However, since the direct reduction of pertechnetate with excess thiourea in a hydrochloric acid solution yields [Tc(tu)6]3+ in high yield [37], direct use of the aqueous solution of the thiourea complex would be preferable for the synthesis of the technetium(III) complex without isolation of the crystals of the thiourea complex. In fact, technetium could be extracted from the aqueous solution of the Tc-thiourea complex with acetylacetone-benzene solution in two steps [38]. More than 95% extraction of technetium was attained using the following procedure [39] First a pertechnetate solution was added to a 0.5 M thiourea solution in 1 M hydrochloric acid. The solution turned red-orange as the Tc(III)-thiourea complex formed. Next, a benzene solution containing a suitable concentration of acetylacetone was added. After the mixture was shaken for a sufficient time (preliminary extraction), the pH of the aqueous phase was adjusted to 4.3 and the aqueous solution was shaken with a freshly prepared acetylacetonebenzene solution (main extraction). The extraction behavior of the technetium complex is shown in Fig. 6. The chemical species extracted into the organic phase seemed to differ from tris(acetylacetonato)technetium(III). Kinetic analysis of the two step extraction mechanism showed that the formation of 4,6-dimethylpyrimidine-... 

Another attempted synthesis of Tc(III)-EDTA and Tc(III)-HEDTA complexes (EDTA ethylenediaminetetraacetic acid HEDTA A -(2-hydroxy-methyl)ethylenediamine-N,AT, iV -triacetic acid) was carried out using [Tc(tu)6]3+ as the starting complex [40]. Technetium-EDTA complexes have been synthesized by the direct reduction of pertechnetate with a suitable reduc-tant in the presence of excess EDTA [41-43]. On addition of EDTA to the Tc(tu) + solution, the intensity of the absorption spectrum decreased with time and the solution color changed from reddish orange to light brown. An electrophoretic analysis for the Tc(III)-EDTA complex showed that more than 70%... 

Technetium carbonyl, 16 66 Technical art history, 11 398 Technical Association of the Pulp and Paper Industry (TAPPI), 21 17 Technical enzymes, 10 310 Technical-grade active ingredient analysis, 18 544... 

The solvent extraction of pertechnetate with cyclohexanone has proved to be an efficient and selective method which can be applied to the separation of Tc from long-lived fission products in the bum-up analysis . The recovery of technetium from the fission products is about 93 %. 

A technique for the determination of Tc amounts as little as 4 x 10 g by neutron activation analysis has been described by Foti et al. . Tc in triply distilled water is irradiated in a thermal neutron flux of 5 x 10 neutrons per cm and per second to produce °°Tc. Other radionuclides are removed by co-precipi-tation with Fe(OH)j. Then, °°Tc is co-precipitated twice with tetraphenylarsonium perrhenate which can be removed by sublimation. The chemical purification of °°Tc requires 40-45 s and the technetium yield is about 53%. 

Trace amounts of Tc are also determined in filter paper and vegetable samples by neutron activation analysis The procedure consists of the following major steps separation of technetium from the sample, thermal neutron irradiation of the Tc fraction to produce °°Tc, post-irradiation separation and purification of °°Tc from other activated nuclides, and counting of the 16 s Tc in a low-background P counter. The estimated detection limits for Tc in this procedure are 5 x 10 g in filter paper and 9 x 10 g in vegetable samples. 

A method has been developed for the determination of technetium-99 in mixed fission products by neutron activation analysis Tc is separated from most fission products by a cyclohexanone extraction from carbonate solution, the stripping into water by addition of CCI4 to the cylohexanone phase, and the adsorption on an anion exchange column. Induced Tc radioactivity is determined using X-ray spectrometry to measure the 540 and 591 keV lines. The sensitivity of the analysis under these conditions is approximately 5 ng. The method has been successfully applied to reactor fuel solutions. 

The atomic absorption characteristics of technetium have been investigated with a technetium hollow-cathode lamp as a spectral line source. The sensitivity for technetium in aqueous solution is 3.0 /ig/ml in a fuel-rich acetylene-air flame for the unresolved 2614.23-2615.87 A doublet under the optimum operating conditions. Only calcium, strontium, and barium cause severe technetium absorption suppression. Cationic interferences are eliminated by adding aluminum to the test solutions. The atomic absorption spectroscopy can be applied to the determination of technetium in uranium and its alloys and also successfully to the analysis of multicomponent samples. 

An isotope dilution mass spectrometric method involves the addition of a known quantity of Tc followed by chemical separation, purification, and measurement of the Tc/ Tc isotopic ratio . An improved technique has been developed for the analysis of Tc in environmental samples. After spiking with Tc the isolated technetium is concentrated onto anion exchange beads. Determination of as little as 1 pg has been achieved through the enhanced ionization efficiency afforded by the resin bead source ... 

This amount of thiocyanate is sufficient for both complete reduction and complex formation. Reduction is allowed to proceed for 30 to 45 s after the addition of the thiocyanate. A bright red color can readily be observed at a technetium (VII) concentration of 0.1 ng per ml. Acetone (6 ml) is then added and the volume of the solution mixed and adjusted to 10 ml with distilled water. At this point, the color has generally developed to less than 50% of its final intensity. Quartz 1-cm glass-stoppered cells are filled with the technetiiun solution and placed in a 20 °C water-cooled spectrophotometer. The extinction will approach a maximum intensity in 1 to 3 h. The maximiun extinction occurs at 510 nm with a molar extinction coefficient and standard deviation of 47,500 + 500 in 60 vol. % of the acetone-aqueous medium. An additional examination of the analysis may be carried out by extract-... 

The Tc complex [TcI(N—Ar)s] (28) (see Section 5.2.2.1.2) can be reduced with Na° in THE to yield the green, nonbridged, dinuclear compound [Tc2(NAr)6] (46), in which three imido-ligands are bound to the Tc center and connected by a single bond to the second technetium. The molecule has a staggered, ethane-like structure and is diamagnetic. Reduction of (28) yields another homoleptic imido-complex of Tc, the imido-bridged, tetrahedral, dinuclear compound [Tc2(/u-NAr )2(NAr )4] (47) (Ar = 2,6-diisopropylphenyl). The conformation could be confirmed by X-ray structure analysis the assumption of a Tc Tc bond is confirmed by the... 

Elemental analysis, fullerene adducts, 44 21 Elemental technetium, see Technetium Element displacement principle, 28 167-198 applications, 28 172-176 theory, 28 169-171 Elements... 

Egorov, O. B., O Hara, M. J., and Grate, J. W., Microwave-assisted sample treatment in a fully automated flow-based instrument Oxidation of reduced technetium species in the analysis of total technetium-99 in caustic aged nuclear waste samples, Anal. Chem., 76, 3869-3877, 2004. 

---