Determination of ionisation constants of radiopharmaceuticals in mixed solvents by HPLC

99mTcI/ReI Tricarbonyl Complexes with Tridentate Cysteamine Based Ligands: Synthesis, Characterization and in vitro/in vivo Evaluation

“…[24] Determination of pK a Values: The pK a values for the Re complexes 1-3 and 99m Tc complexes 1a-3a were determined by previously described HPLC methods. [15,32] The pK a values were determined on a Perkin-Elmer LC pump 200 coupled to a LC 290 tunable UV/ Vis detector and a Berthold LB-507A radiometric detector, with a PRP1 (250 ϫ 4.1 mm, 10 μm, Hamilton) reversed phase column run under isocratic conditions with a flow rate of 1.0 mL/min and at room temperature. The mobile phase was acetonitrile:phosphate buffer (0.01 m), 60:40.…”

“…The aqueous ionization constants pK a were calculated from the pK HPLC values after correction with a predetermined correction factor obtained from analysis of standard amine compounds. [32] In vitro Binding to Melanin: The melanin binding affinity of 1a-3a was assessed with synthetic tyrosine-melanin (Sigma). The general procedure was as follows: an aliquot of the radioactive preparations of 1a-3a (100 μL) was added to a melanin suspension (0.5 mg/ 10 mL) in distilled water.…”

Technetium-labeling of monoclonal antibodies with functionalized BATOs: 2. TcCl(DMG)3CPITC (CPITC=carboxyphenylisothiocyanate) labeling of B72.3 and NP-4 whole antibodies and NP-4 F(ab')2

“…The carboxylic acid substituent is presumably in the ionized form at the pH (9.0) at which protein labeling occurs, creating a complex with a net 1charge. This conclusion is drawn from HPLC data, where it is observed that complex retention time varies significantly in the pH range 4.6-5.0, indicating that the apparent pK& of the carboxylic acid is close to this range (19)(20)(21).…”

“…The Effects of pH, Temperature, and Heating Time on the RCP of ""TcC1(DMG)3CPITC. ""TcCl-(DMGlsCPITC was prepared by adding (OH^B-CPITC (3 mg) in ethanol (50 gL) and ""TcOv (1.0 mL, [20][21][22][23][24][25][26][27][28][29][30] mCi) to a freeze-dried kit containing DMG. The effects of heating temperature (70-100 °C), heating time (5-50 min), and pH (2.0-4.0) on the RCP of the labeling reagent were evaluated as was described for TcC1(DMG)3PITC in ref 1.…”

The Determination of Charge of Cationic99mTc-Radiopharmaceuticals

“…This relied upon the addition of an organic modifier to the eluent in sufficient quantities to minimise the contribution of hydrophobic interactions to Q. We did not conduct a systematic study to select the most appropriate organic modifier; acetonitrile was selected as it appeared to have little effect on the activity coefficient of the chosen competing ion and it had previously been used successfully as the organic modifier in an HPLC method for the determination of pKa of technetium chelates[30]. The column dead-time (Ro) was determined using a nonretained marker (nitrate).…”