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  • Author or Editor: J. Jovanović x
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Abstract  

The results obtained for radiochemical purity of ITLC (SA) and (SG) using different solvent systems and low voltage electrophoresis are presented in the paper. Radiochemical purities obtained for99mTc-dimethyl IDA (99mTc-HIDA) and99mTc-diethyl IDA (99mTc-EHIDA) are 98.1±0.6% and 98.7±0.5%, respectively. Variable99mTc hydrolyzate contents, depending on the ionic strength of the eluents and on the time interval between labelling and analysis, have been obtained by Sephadex chromatography. The eluent containing Sn-EHIDA inhibits dissociation of99mTc-EHIDA due to dilution of the preparation during elution of the column and yielding only a small percent of Sephadex bound fraction, as compared to other investigated eluents. The range of normal99mTc-IDA biodistribution values in the organs of experimental animals and statistical significance of the difference between these two preparations have also been determined. The results obtained for99mTc-HIDA and99mTc-EHIDA in the liver are 33.9±5% and 25.7±4.7%, respectively p<0.01.

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Abstract  

An electrophoretic method to control the radiochemical purity of chlormerodrin-203 is described. Optimum conditions for the separation of inorganic and organically bound mercury-203 were determined by investigating its mobility in the concentration range of 1·10−5–1·10−2 M NaCl. Maximum separation, of203Hg and hydroxychlormerodrin was achieved at 0.05M NaCl, at the potential gradient of 8V/cm for 2 hrs.

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Summary  

Kinetics of dehydration of equilibrium swollen poly(acrylic acid) hydrogel was investigated using methods of non-isothermal thermal analysis. Methods of Kissinger, Coats-Redfern, Van Krevelen and Horowitz-Metzger were applied for determination the kinetics parameters: activation energy (E), pre-exponent (lnA) as well as the kinetics model ƒ(69) for the process of hydrogel dehydration under different heating rates. An existence of good agreement between determined values of kinetic parameters (Eand A), which were obtained applying different methods under the same heating rate. Functional relationship between changes of kinetic parameters of dehydration and changes of heating rate was established. An existence of compensation effect is accepted and explanation of compensation effect appearance during the hydrogel dehydration is suggested.

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Abstract  

An isothermal dehydration of equilibrium swollen poly(acrylic acid) hydrogel in the temperature range from 306 to 361 K was investigated. The specific parameters connected with shape of the conversion curves were defined. The activation parameters (E, lnA) of the isothermal dehydration of equilibrium swollen poly(acrylic acid) hydrogel were calculated, using Johnson-Mehl-Avrami (JMA), ‘initial rate’ and ’stationary point’ methods. The reaction models for the investigated dehydration are determined using the ‘model-fitting’ method. It was established that both, the reaction model and activation parameters of the hydrogel dehydration were completely different for the isothermal process than for the non-isothermal one. It was found that the increase in dehydration temperature lead to the changes in isothermal kinetic model for the investigated hydrogel dehydration. It was established that the apparent activation energy (E) of hydrogel dehydration is similar to the value of the molar enthalpy of water evaporation.

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Abstract  

“Kit” composition was determined on the basis of biodynamic data obtained when the Sn/pyrophosphate ratio, pH and other parameters were varied. In vivo distribution of different99mTc-Sn-pyrophosphate complexes permitted the selection of the most suitable complex for skeletal scanning.

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Abstract  

The results of radiochemical purity measurements for99mTc–S colloid, 90.7±1.4, and99mTc–Sn colloid, 98.9±1.2 obtained by ITLC (SG) with 80% methanol are given. The range of biodistribution normal values for99mTc colloid preparations for animal organs is determined. The results of99mTc–S and99mTc–Sn colloid distribution in liver are 95.4±6.1% and 100,0±5.4%, respectively.

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Abstract  

The partition coefficient (log P) for n-octanol/water system was calculated applying PACO program for various theoretically possible mono and dihalogenated IDA derivatives. Some of the synthesized ligands (SOLCOIODIDA, IODIDA and DIIODIDA) were labeled with the technetium-99m. The biodistribution and influence of bilirubin on their biokinetics were investigated in rats. The correlation between partition coefficients of ligands increase (log P) and better hepatobiliary properties of 99mTc-IDA derivatives was determined. The values of log P increase from 1.16 for SOLCOIODIDA, 3.11 for IODIDA to 3.47 for DIIODIDA. In correlation with these results, biliary excretion decreased for 59% for 99mTc-SOLCOIODIDA and 11% for 99mTc-IODIDA and 99mTc-DIIODIDA under hyperbilirubinemia (3.5 min after injection) and 45%, 11% and 0.38% respectively (15 min after injection). The highest biliary excretion had 99mTc-DIIODIDA (55.4% for 3.5 min). Considering the correlation between hepatobiliary properties and log P, the evaluation of biological properties for various trifluoromethyl mono and dihalogenated IDA derivatives was performed on the basis of the calculated log P in order to synthetize a new radiopharmaceutical for hepatobiliary scintigraphy.

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Journal of Thermal Analysis and Calorimetry
Authors: L. Katsikas, K. Jeremic, S. Jovanovic, J. Velickovic, and I. Popovic

Abstract  

The effect of molar mass and, in the case of dextran, of the degree of branching on the thermal degradation kinetics of dextran and pullulan was studied in the presence and absence of oxygen. Although the initial mass loss of the dextran samples occurred at higher temperatures than that of the pullulan samples, the overall thermal degradation activation energies were lower for dextran than for pullulan. In the case of dextran the thermal stability was found to decrease with molar mass and degree of branching. The molar mass of pullulan, in the range of 104 to 105 g/mol, appeared to have no significant influence on the thermal characteristics of the samples.

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Abstract  

Two methods for the determination of radiochemical purity of preparations labeled with99mTc are described. Paper chromatography was used for separation of reduced99mTc and free pertechnetate from the labeled radiopharmaceutical. Whatman 3MM paper was used first with a acetone and then with 1N NaCl, as the mobile phase. Instant thin layer chromatography was performed for comparison. The electrophoretic method was also applied, using 0.05 M Na-acetate and 0.017 M NaCl. Biodistribution of99mTc-DMSA in the organs of experimental animals was followed in order to verify chemical control methods.

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Abstract  

The effective resonance energy
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, a useful parameter when correcting the resonance integral for a non-ideal epithermal neutron flux distribution, can be experimentally determined by coirradiating the investigated isotope with a comparator isotope whose effective resonance energy is accurately known. The principle of the method is outlined and the error propagation functions are studies in detail. The usefulness of the
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-comparator technique is tested for a few isotopes.
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