Malay Kanti Das

Recovery of 99mTc from Na2[99Mo]MoO4 solution obtained from reactor-produced (n,γ) 99Mo using a tiny Dowex-1 column in tandem with a small alumina column☆

A simple separation technique of (99m)Tc from Na(2)[(99)Mo]MoO(4) in sodium hydroxide solution obtained from the (98)Mo(n,gamma)(99)Mo reaction is described. Low to medium specific activity (99)Mo-molybdate solution of 7.4-18.5GBq (200-500mCi) in sodium hydroxide was passed through a tiny Dowex-1 column (25mg) to separate the (99m)Tc from the (99)Mo; subsequently the (99m)Tc was eluted from the Dowex 1 column with tetrabutylammonium bromide (TBAB) solution (1mg/5ml methylene chloride). The TBAB solution was passed through a small alumina column (1.5g) where the (99m)Tc is retained and separated from TBAB and CH(2)Cl(2). Technetium-99m from the alumina column was finally eluted with 5ml saline leaving any traces of (99)Mo on the alumina column. The separation yield was about 90% (n=10). The method has applicability for decontamination of (99g)Tc from spent (99)Mo waste solution and recovery of (99g)Tc for research use. The procedure should also be equally applicable for recovery of (188)ReO(4) from (188)WO(4) in a radioisotope laboratory.

A novel technique for the effective concentration of 99mTc from a large alumina column loaded with low specific-activity (n,γ)-produced 99Mo☆

Molybdenum-99 of low-to-medium specific activity, 7.4-14.8 GBq/g, obtained by the (98)Mo(n,gamma)(99)Mo reaction in research reactors requires a large alumina column to adsorb the molybdenum since the capacity of alumina to adsorb Mo is limited (20 mg Mo/g of alumina). The large size of alumina column, in turn, requires large eluant volumes to elute the (99m)Tc, and the radioactive concentration (RAC) of the pertechnetate becomes unacceptably low for radiopharmaceutical applications. This study describes a method for obtaining high RAC pertechnetate solutions from a column generator loaded with (99)Mo of low specific activity. Molybdenum-99 of specific activity, 7.4 GBq/g, was absorbed on an alumina column [60 g, 70 mm, (H) x 35 mm (diam.)]. The (99m)TcO(4)(-), eluted with 60 ml normal saline (0.15N NaCl), was applied to a 12 mm (H) x 1 mm (diam.) column containing 15 mg of the strong anion exchanger Dowex 1 x 8. The retained pertechnetate was eluted with 5 ml of 0.5 mM tetrabutylammonium bromide (TBAB) solution in methylene chloride. The organic solvent was subsequently removed under vacuum and the dry residue was reconstituted with the desired volume of normal saline. All the operations were carried out in a closed cycle with sterile connecting tubes and multi-way stop-cocks. The concentrated pertechnetate obtained contained about 90% of the total saline eluate and had a pH of 6-7, a radiochemical purity (RCP) consistently >99%, the (99)Mo breakthrough was around 10(-4)%. Colorimetric spot tests (limit tests) for Al and Mo showed <10 ppm in the final (99m)TcO(4)(-) solution. The RCP of the labelled compounds prepared using the pertechnetate obtained and five different radiopharmaceutical kits were >95%. The procedure may be equally applicable for the effective concentration of (188)ReO(4)(-) from (188)W-(188)Re generators.

A computerized compact module for separation of 99mTc-radionuclide from molybdenum

An automated closed cycle module for the separation and recovery of various isotopes, radioactive or non-radioactive, using solvent extraction and column chromatography techniques, and in particular, for separation and recovery of (99m)Tc from low-medium specific activity (99)Mo, is described. The module may also be applicable for separation of (99m)Tc produced in a cyclotron. The module is safe and reliable to avoid human interference and hazards posed by handling of radioactive and hazardous chemicals. The entire system of automation includes a user-friendly PC based graphical user interface (GUI) that actually supervises the process via an embedded system based electronic controller.

A cation exchange method for separation of 111In from inactive silver, copper, traces of iron and radioactive gallium and zinc isotopes

Abstract 111 In was produced by the 109 Ag(α, 2n) 111 In reaction. A simple radiochemical separation technique, using Dowex-50 cation exchange resin (with prior removal of copper bulk, if present), has been employed to separate radioindium from inactive contaminants like Ag, Cu, Fe and active contaminant like 67 Ga and 65 Zn. The radiochemical separation yield was 90–99%. The radionuclidic purity of 111 In was >99% at 60 h after EOB. The level of all the inactive contaminants was μ g/mL in the final product.

Preparation and evaluation of 99mTc-cefuroxime, a potential infection specific imaging agent: a reliable thin layer chromatographic system to delineate impurities from the 99mTc-antibiotic.

Technetium-99m labelled cefuroxime, a second-generation cephalosporin antibiotic and potential bacteria specific infection imaging agent was evaluated. A good radiochemical purity (95%) of the labelled product was obtained after filtering the reaction mixture through a 0.22 μm filter. Scintigraphy study of the purified product showed uptake in infectious lesions 45 min after injection and abscess-to-muscle ratios were found to be 1.80, 1.85 and 1.88 at 45 min, 1.5 hr and 3 hr, respectively. A versatile and reliable chromatographic technique to assess the radiochemical purity of (99m)Tc-cefuroxime has also been described.

Polymers derived from Xanthomonas campesteris and Cyamopsis tetragonolobus used as retardant materials for the formulation of sustained release floating matrix tablet of atenolol

The objective of the present study was to develop, optimize, in vitro, and in vivo evaluation of floating matrix tablet of atenolol using polymer blend derived from Xanthomonas campesteris and Cyamopsis tetragonolobus that are characterized by release requirements of sustained-release product and to improve the oral bioavailability of the drug. A 3(2) full factorial design was employed to optimize the tablets, where content of polymer blend (X1) and ratio of xanthan gum-to-guar gum (X2) were considered as independent variables. The effects of independent variables on dependent variables, i.e. floating time, diffusion exponent, and time to release 50% of atenolol were evaluated. The in vivo pharmacokinetic parameters of the optimized formulation were compared with the marketed sustained release formulation of atenolol (Aten(®)). The optimized formulation containing 20% (w/w) of polymer blend and 50:50 ratio of xanthan gum-to-guar gum was able to float more than 12h and showed the desired sustained drug release from the tablets. In vivo retention studies in rabbit stomach showed the gastric residence of tablet up to 6h. The in vivo study of optimized tablets illustrated significant improvement in the oral bioavailability of atenolol in rabbits. It can be concluded that floating matrix tablet of atenolol prepared by using xanthan gum and guar gum has potential for sustained release of the drug as well as improved oral bioavailability through enhanced gastric residence time of formulation in stomach.

Radiochemical separation of high purity 111In from cadmium, copper, aluminium and traces of iron: Use of a cation exchange resin with hydrobromic acid and hydrochloric acid

Abstract 111In was obtained by a two-step separation procedure from an irradiated cadmium target, extending the method developed earlier by the authors for silver targets. The overall yield was 90–95% and the purity of the 111In was compatible with medical applications.

Production of 61Cu using natural cobalt target and its separation using ascorbic acid and common anion exchange resin.

(61)Cu was produced by (nat)Co(α, xn)(61)Cu reaction. (61)Cu production yield was 89.5 MBq/μAh (2.42 mCi/μAh) at the end of irradiation (EOI). A simple radiochemical separation method using anion exchange resin and ascorbic acid has been employed to separate the product radionuclide from inactive target material and co-produced non-isotopic impurities. The radiochemical separation yield was about 90%. Radiochemical purity of (61)Cu was >99% 1 h after EOI. Final product was suitable for making complex with N(2)S(2) type of ligands.

Purification and stabilization of 99mTc-d,l-HMPAO: role of organic extractants

99mTc-d,l-HMPAO, an important SPECT agent for imaging cerebral perfusion, suffers from the disadvantage of an inherent instability and its shelf life has been reported to be 30 min. The latter is a harsh constraint and not compatible with Centralized Radiopharmacy procedures. During the attempts to improve upon the stability of 99mTc-d,l-HMPAO, preservation of product as an organic extract into suitable solvents like diethylether, ethylacetate, methylethylketone, chloroform was tried out. Chloroform extraction (yield: >90%) resulted in a product having stability not less than 5 hours. Gentle drying of the chloroform extract and reconstitution in normal saline resulted in quantitative recovery of 99mTc-d,l-HMPAO with acceptable radiochemical purity (>90%). This finding is thus of much significance, especially in the context of centralized large hospital radiopharmacy setting, by rendering convenience and flexibility in scheduling patients.

Ethylene dicysteine (EC) and ethyl cysteinate dimer (ECD) complexes of Ga(III) and In(III)

Ethylene dicysteine (EC) and ethyl cysteinate dimer (ECD) complexes of67Ga and111In were prepared and the complexation yield and radiochemical purity estimated by paper chromatography, paper electrophoresis and solvent extraction into chloroform.111In-EC was found to be anionic, whereas111In-ECD was neutral. EC complexes of67Ga and111In were stable upto 6 hours and expectedly less lipophilic than ECD complexes. ECD complexes of67Ga and111In were unstable in aqueous medium, but highly stable in chloroform. The utility of the work for stabilisation of products as organic extract and the possible role and limitation for the development of new68Ga radiopharmaceuticals and of bifunctional chelating agent (BCA) for111In are discussed.