Measuring the RCP

The chromatographic conditions were as follows: HPLC, Waters 66E Controller pump, HYPERSIL C18 column (250 mm × 4.6 mm, particle size of 5.0 μm), column temperature of 25°C, ultraviolet wavelength λ = 280 nm, the mobile phase A solution was 0.1% trifluoroacetic acid (TFA), the B solution was acetonitrile containing 0.1% TFA, and the elution gradient of B was 10% to 90%. The ^99mTc-TP1623 solution (50 μl) was diluted to 100 μl with a phosphate buffer saline (PBS) solution. A sample of diluent (50 μl) was prepared and added to the pump at room temperature. The flow speed was 0.6 ml/min and the analysis time was 16 min. The eluate was collected with tubes at different periods; each tube had 0.3 ml eluate. The radioactive count (CPM) in each tube was measured by a γ immunoassay instrument (Anhui ZhongJia Optoelectronic Instrument Company, Hefei, China), and the elution time–radioactivity curve (T–A curve) was drawn. The RCP was calculated according to the following formula: