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Abstract
The objective of this thesis can be divided into three parts.the first part deal with the invistigation of optimum conditions for labeling of Evan blue via electrophilic substitution reaction. The second part involves the nucleophilic radioiodination of o-iodohippuric acid (o-IHA). The third part involves the nucleophilic radioiodination of m-iodohippuric acid (m-IHA) by dry method.
1- Electrophilic radiiodination of Evan blue was carried out by using several oxidizing agents such as chloramine-T, iodegen and N- bromosuccinamide. The factors affecting the percent of the radiochemical yield such as substrate concentration, oxidizing agent concentration, reaction temperature, reaction time and pH were studied. Optimization of the radiochemical yield resulted in 55.5% for radioiodo Evan blue when the reaction was carried out in 0.26 mM EB, 1.76mM CAT and 3.7 MBq Na125I at 60 oC and 0.1M phosphate buffer (pH=2.0) within 5 minutes.
The stability of the purified labeled compound (125IEB) was carried out to determine the suitable time of injection at which no side products can be occurred.
2- (a) A nucleophilic radioiodination of o-iodohippuric acid (o-IHA) has been investigated. Dimethylformamide (DMF) has been used as a solvent. Hippuran contains CONHCH2COOH moiety, which promotes tubular excretion of organic anions. Different parameters such as the effect of temperature, o-IHA content, different solvents and reaction time have been investigated by using 1.3 mM, of o-IHA in DMF as a solvent at 150 °C and 3.7MBq 125I . About 96.5% of radiochemical yield without catalyst has been produced. Also it was found that the activation energy, E, for this substitution reaction was 14.2 kJ / mol.
(b) Separation and purification of the product (o-125IHA) was achieved by high performance liquid chromatography (HPLC) under special condition.
3- Using the dry state on m-IHA, a yield of about 93.6%, at 165 °C was obtained by using 2 mg of tetrabutyl ammonium bromide (TBAB). The activation energy of the exchange reaction between m-IHA and Na125I, without catalyst and in presence of TABAB in dry state has been studied. In dry state without catalyst, the activation energy was found 7.60 kJ / mol. But using TABAB, it was found to be 4.76 kJ / mol. The product was analyzed by using TLC-SG in developing solvent consisting of n-butanol: acetic acid: water in the ratio 4:1:1.