Volume 99, Issue 5 -

The sorption of americium(III), (Am(III)), onto kaolinite was studied in batch experiments in the absence and presence of humic acid (HA) ([Am(III)] 0 =1×10 −6 ߙM, [HA] 0 =0 or 10ߙmg/L, I =0.01ߙM NaClO 4 , pH=3–10, p CO2 =10 −3.5 ߙatm, solid-to-liquid ratio (S/L)=1 or 4ߙg/L). The results show that the Am(III) sorption onto kaolinite is influenced by S/L, the presence of HA and the pH value. In the absence of HA, Am(III) exhibits a very strong and almost pH independent sorption onto kaolinite at the S/L ratio of 4ߙg/L. In the presence of HA, there are small differences in the Am(III) sorption compared to the HA free system. At pH values 5, HA very slightly enhances the sorption of Am(III). Conversely, at pH values ≥5.5, the presence of HA decreases the sorption of Am(III) due to the formation of dissolved Am(III) humate complexes. The decrease of S/L from 4 to 1ߙg/L has a significant effect on the Am(III) sorption onto kaolinite. A sorption edge occurs at pH 6 and the influence of carbonate on the Am(III) sorption at higher pH values becomes evident. Furthermore, the influence of HA on the Am(III) sorption onto kaolinite is more pronounced. The Am(III) sorption results are compared to literature data and to those of U(VI) sorption onto kaolinite obtained under the same experimental conditions.

Some ternary and quaternary complexes of thorium(IV) with the general formula [Th(OOCCH 3 ) 2− n (SB) n (OOCC 15 H 31 ) 2 ] (HSB=Schiff bases and n =1 or 2) have been synthesized by the stepwise substitutions of acetate ions from thorium(IV) acetate, first with straight chain carboxylic acid and then with Schiff bases. The complexes are characterized by elemental analyses, spectral (electronic, infrared, 1 H NMR, FAB mass, photoluminescence and powder XRD) and TEM studies. Conductance measurements indicated non-conducting behaviour of the complexes. Structural parameters from powder XRD data for complexes 5 and 6 which indicate poorly crystalline nano-sized triclinic particles. Electronic absorption spectra of the complexes showed π → π * and n→ π * charge transfer transitions. All complexes displayed fluorescence and a correlation was sought between luminescence spectra of complexes in solution at room temperature. On the basis of physico-chemical studies, coordination number 8 was assigned for thorium(IV) in the complexes. The morphology and microstructure of the complexes were examined with transmission electron microscopy (TEM) and the selected area electron diffraction (SAED).

Thorium complexation with gluconate has been studied from solubility experiments at gluconate concentrations between 10 −6 and 10 −1  mol/l, with pH c between 9 and 13 and I =0.5 M (NaClO 4 ). Solubility experiments indicate the formation of a 1:1 thorium:gluconate complex. The stability constant for this species, extrapolated to I =0 by using the SIT (specific interaction theory), has been determined to be log 10 Kº=−11.5 ± 0.6 for the reaction: Th 4+ + GH 4 − + 2H 2 O = Th(OH) 2 (GH 2 ) − + 4H + . In the presence of ThO 2 · x H 2 O, sorption of the organic ligand onto solid surface seems to limit thorium dissolution.

Burn-up measurement for the fast reactor fuels in general and measurements on short cooled dissolver solutions in particular pose a great challenge due to the high level of radioactivity associated with the solution. An HPLC technique using monolith support has been developed for the first time for the determination of burn-up of fast reactor fuels and applied to the dissolver solution of the FBTR (Fast Breeder Test Reactor, Kalpakkam, India) fuel discharged at nominal burn-up of 150 GWd/t. A dynamic ion-exchange technique developed for the individual separation of lanthanides as well as actinides in connection with the burn-up measurements, has led to separation of all 14 lanthanides in about 2.77 min, the fastest LC technique as of now in literature and has resulted in a significant reduction in analysis time, radiation dose to operator and liquid waste generation. The dissolver solution was injected directly into the HPLC and assayed for lanthanide fission products, uranium, and plutonium using appropriate dilutions. The atom percent fission was calculated based on these measurements and the results are discussed. A reversed-phase chromatographic technique was also employed for the determination of uranium and plutonium in the dissolver solution. The sorption behaviour of uranium and thorium was examined on a monolith support modified with bis-2-ethylhexyl succinamic acid (BEHSA). Rapid separation of uranium from thorium could be achieved in about 20 s on the modified monolith support.

Radioactively labeled trace gases have been successfully used to study heterogeneous chemistry of atmospheric relevance. Here we present a new synthesis of gas-phase peroxynitric acid labeled with 13 N (H 13 NO 4 ) to study the interaction of HNO 4 with ice and snow surfaces. A yield of about 30% for HNO 4 was determined. The main by-products were HNO 3 and HNO 2 . Exposure of an ice packed bed flow tube to these species revealed that the interaction with the surface scale in the order HNO 3 ߙ>ߙHNO 4 ߙ=ߙHNO 2 ߙ>ߙNO 2 .

The effect of solvent on nucleophilic substitution with cyclotron-produced [ 18 F]fluoride was studied in polar aprotic (CH 3 CN and DMF) and protic solvent ( t -BuOH and t -amyl alcohol) mixtures (CH 3 CN/co-solvent, 2:8) in a series of model compounds, 4-(R 1 -methyl)benzyl R 2 -benzoates, using a K2.2.2/[ 18 F]KF phase transfer system (R 1 =–Cl, –OMs or –OH; R 2 =–Cl, –I or –NO 2 ). 18 F-fluorination of compounds 1–3, with chloride or mesylate as a leaving group in the benzylic position (R 1 ), afforded the desired 4-([ 18 F]fluoromethyl)benzyl analogues in all solvents during 15ߙmin reaction time. The highest radiochemical yields (RCY) in all the studied reaction temperatures (80, 120 and 160ºC) were achieved in CH 3 CN. Radiochemical yields in protic solvents were comparable to RCY in CH 3 CN only with the sulfonate ester 3 as a starting material. 18 F-Fluorination of the benzylic halides 1 and 2 was not promoted in the same extent; in addition, labelled side-products were detected at higher reaction temperatures. Radiofluorination in tert -alcohols was also studied using [ 18 F]CsF with and without added phase transfer catalyst, resulting in both conditions lower RCY when compared to K2.2.2/[ 18 F]KF system. Protic solvents were not able to promote aromatic 18 F-fluorination. 18 F-Fluorination of compound 5, having para -activated nitro group in the aromatic position (R 2 ), failed in tert -alcohols even at the highest temperature, but it was labelled successfully in DMF and to some extent in CH 3 CN.

An antitumor agent paclitaxel (PAC) has been proved to be efficient in the treatment of breast and ovarian cancer. Glucuronic acid-derived paclitaxel compound [paclitaxel-glucuronide (PAC-G)] was enzymatically synthesized using microsome preparate separated from rat livers. The biodistribution mechanism of PAC-G in healthy female Albino Wistar rats has been investigated. The expected structure is confirmed according to LC/MS results, and the possible attachment is to C2-hydroxyl group. PAC-G was labeled with 99m Tc and the radiochemical yield of radiolabeled compound ( 99m Tc-PAC-G) was 98.0±02.74 ( n =9). The range of the breast/blood and breast/muscle ratios is approximately between 3 and 35 in 240ߙmin. All these experimental studies indicate that 99m Tc-PAC-G may potentially be used in breast tissue as an imaging agent.

In this work we report the synthesis, characterization and biological evaluation of two new neutral tricarbonyl fac -M(CO) 3 (NNO) (M=Re, 99m Tc) derivatives of WAY-100635 as potential 99m Tc agents for the in vivo imaging of 5HT 1A receptors. The new pharmacophore NNO ligands are based on the picolylamine N , N -diacetic acid (PADA) ligand and their synthesis was achieved through the PADA anhydride, showing thus the applicability of this synthetic approach, developed in our laboratory, for the incorporation of bioactive amines in the PADA molecule and the development of target specific radiopharmaceuticals. The rhenium complexes were synthesized using [NEt 4 ] 2 [Re(CO) 3 Br 3 ] as a precursor and fully characterized by elemental analysis and spectroscopic methods. The analogous technetium-99m complexes were also prepared quantitatively using the [ 99m Tc(CO) 3 (H 2 O) 3 ] + precursor and their structure corroborated by means of the rhenium complexes. The lipophilicity of the Tc complexes is in the range normally accepted for substances to be able to cross the BBB. Competition binding tests showed moderate affinity for the 5HT 1A receptors, with IC 50 values at the nanomolar range (30 and 116 nM). Biodistribution in healthy animals was characterized by high initial blood and liver uptake and fast blood and tissue depuration with excretion taking place mainly through the hepatobiliary system. None of the new complexes showed any significant brain uptake, suggesting that the ability of a compound to cross the BBB is determined by more factors than charge, lipophilicity and size.