Usefulness of fast protein liquid chromatography as an alternative to high performance liquid chromatography of 99mTc-labelled human serum albumin preparations.
Accurate analysis of the radiochemical purity of 99mTc-labelled preparations is usually performed using an appropriate high performance liquid chromatography (HPLC) system. For the analysis of 99mTc-HSA, the European Pharmacopoeia (Ph. Eur.) prescribes an HPLC system using silica gel for size-exclusion chromatography as the stationary phase. Analysis of 99mTc-HSA preparations with this method allows one to distinguish radiolabelled polymeric, oligomeric, dimeric monomeric forms of albumin as well as small molecular mass impurities such as pertechnetate (99mTcO4-). Due to the relatively short lifetime of this type of column, two fast protein liquid chromatography (FPLC)-type columns were evaluated for their possible usefulness for quality control of 99mTc-HSA preparations, namely Superdex 200 HR 10/30 and Superdex 75 HR 10/30 (Pharmacia, Sweden). Both columns contain a matrix produced by the covalent bonding of dextran to highly cross-linked porous agarose beads. The fractionation range of the Superdex 75 HR 10/30 column was too low to obtain an adequate separation between albumin and its polymerized forms and this column was therefore considered unsuitable for the analysis of 99mTC-HSA preparations. The Superdex 200 column afforded the same pattern and relative amounts of albumin and its polymerized forms as the silica column although the resolution obtained was somewhat lower. A major difference was the fact that 99mTcO4- could not be eluted from the Superdex column but was eluted from the silica column, whereas other small molecular mass, negatively charged 99mTc complexes such as 99mTc-diethylene triamine pentaacetic acid showed an identical elution pattern on both columns. The presence of pertechnetate in 99mTc-HSA preparations, however, can easily be checked using paper chromatography (PC) and acetone as the eluent. Since the lifetime of the Superdex column is twice that of the silica column, FPLC in combination with PC can be recommended as a money-saving and efficient analytical technique for the quality control of 99mTc-HSA preparations.