Determination on Radiochemical Purity of Labelled Protein With Centrifugal Ultrafiltration

To explore the determination of radiochemical purity(RCP) of labelled protein with centifugal ultrafiltration, the radiochemical purity of ¹²⁵I-AAFP(anti-allergy fusion protein) was determined and compared by high performance liquid chromatography(HPLC), trichloroacetic acid(TCA) precipitation and centrifugal ultrafiltrations. It shows that three methods can separate the labelled ¹²⁵I-AAFP and free iodine-125 efficiently. The lower, middle and higher radiochemical purity of ¹²⁵I-AAFP which are determined by centrifugal ultrafiltration, TCA and HPLC  respectively are 0.62%±0.21%, 7.25%±1.38% and 0.97%±0.12%; 61.58%±0.52%, 63.18%±1.98% and 63.77%±1.23%; 98.89%±0.31%, 98.76%±0.41% and 98.80%±0.82%. When RCP of ¹²⁵I-AAFP is very lower, the RCP measured with HPLC is not different from that with centrifugal ultrafiltration(P>0.05), whereas lower than that with TCA(P<0.05). Except this, there are no significant differences in the RCP of ¹²⁵I-AAFP determined with three different methods (P>0.05). Centrifugal ultrafiltrations can be used to determinate the radiochemical purity of labelled protein.