Rapid determination of the radiochemical purity of 99mTc-antimony trisulfide colloid prepared by standard and alternative heating methods.
The purpose of this study was to validate a rapid quality control method for the lymphoscintigraphic tracer 99mTc-antimony trisulfide colloid (99mTc-ATC).


METHODS
ATC was labeled with 99mTc according to the manufacturer's instructions as well as by alternative heating conditions designed to provide a range of percentages of radiochemical purity (RCP): the tracer was prepared in a dry block heater with heating cavities of different sizes, the temperature of the heating block was varied from 70 degrees C to 115 degrees C, or the duration of heating was varied from 15 to 35 min. Anion-exchange minicolumns were trialled to separate any 99mTc-pertechnetate impurity from 99mTc-ATC with physiologic saline as the eluent. Quality control results were compared with the results from the manufacturer's recommended method, which uses an instant thin-layer chromatography (ITLC) strip with saline as the migrating solution.


RESULTS
The quality control results obtained with a cartridge method in 2-3 min compared favorably with those obtained with the ITLC method with saline when the tracer was prepared by heating at 115 degrees C in a dry block heater for 35 min (RCPs, 99.4%+/-0.3% [mean+/-SD] and 99.2%+/-0.3%, respectively; n=25). The cartridge and ITLC quality control results also were in excellent agreement (correlation coefficient, 0.99) over a range of RCPs (80%-100%). An alternative anion-exchange cartridge that was tested in this study was not suitable for assaying the RCP of 99mTc-ATC because of the complete retention of 99mTc-pertechnetate on the sorbent.


CONCLUSIONS
Compared with the established ITLC method, the cartridge quality control method tested in this study is rapid and provides a reliable assessment of the RCP of 99mTc-ATC. For the preparation of 99mTc-ATC, a dry block heater can be successfully substituted for a boiling water bath and is recommended for heating at high altitudes.
Smyth
Douglas R
DR
RAH Radiopharmacy, Department of Nuclear Medicine, Royal Adelaide Hospital, Adelaide, South Australia, Australia. dsmyth@mail.rah.sa.gov.au
D000965:Antimony / Q000032:analysis* / Q000737:chemistry*; D002845:Chromatography / Q000379:methods*; D006358:Hot Temperature; D011785:Quality Assurance, Health Care / Q000379:methods*; D019275:Radiopharmaceuticals / Q000032:analysis*; D017556:Technetium Compounds / Q000032:analysis* / Q000737:chemistry*; D013997:Time Factors
D019275:Radiopharmaceuticals; D017556:Technetium Compounds; C019096:technetium Tc 99m antimony sulfide; D000965:Antimony