Objective:
ITLC-SG is routinely used method in determining the RCP for 99mTc-Sestamibi. But the methodology is complicated and time-consuming as it involves 2 different solvent systems to separate impurities; i.e. free pertechnetate (TcO4-) and colloids (TcO2). This study was undertaken to assess other methods which are fast, convenient, reliable and without compromising high RCP.

Materials and Methods:
99mTc-Sestamibi was prepared according to the Standard Operating Procedure of this department by adding 5GBq 99mTcO4- in 2.6ml saline. To ensure uniformity, we used the same split kits in all 4 different systems viz. ITLC-SG (acetone/saline), Whatman-1 [Chloroform:Methanol (75:25v/v)], and Sep-Pak method using 2 different solvents (eg. ethanol and ethyl acetate) after pre-treating the cartridge with dilute Hydrochloric acid (0.001M))

Results & Discussion:
RCP for 99mTc-Sestamibi was >94%, using ITLC-SG method, which is comparable to the results obtained with Whatman-1 chromatography system. However, chloroform used in the latter method is highly volatile and has to be prepared fresh every time. In the routine practice it is a big limitation. On the other hand, the RCP was >97% in the case of Sep-Pak method using ethanol as the solvent system; but lower RCP (<90%) was obtained when ethyl acetate was used as the solvent, and therefore not desirable.

Conclusions:
Sep-Pak method using ethanol as solvent seem to be much better than other systems studied, as it yielded higher RCP, faster to perform, and offered consistent results than other methods. The only limitation is the cost, which may be higher than other systems.