TABLE 1.
Troubleshooting table.
| step | problem | possible reason | solution |
|---|---|---|---|
| 10 | Precipitation | Cu+ complex precipitates out because of its poor solubility in aqueous solution |
Continue adding the organic solvent (e.g., MeCN) until the reaction is clear |
| 15 | Defluoridated product | AMBF3 may start losing fluoride when the reaction pH is too basic (pH >12). The defluoridated product, AMB(OH)2-TATE, can be determined by mass spectrum, and it is separable from AMBF3-TATE by using method B (Reagent Setup) |
Adjust the final pH of the click reaction to 7–12 with phosphate buffer |
| 17A(i) | Low efficiency of 18F fluoride elution (<80%) |
Rate of elution is too fast | Elute 18F fluoride slower (one drop for each 10 s) |
| 19 | Low efficiency when ‘trapping’ radiolabeling mixture with C18 cartridge (<10%) |
The product is too polar for C18 purification, or the pH of the reaction mixture is significantly different from the isoelectric point of the peptide |
Adjust the pH value of the crude reaction to the pH that is similar to the isoelectric point of the peptide |
| 20 | Low efficiency when ‘releasing’ radiolabeled product from C18 cartridge (<50%) |
The solubility of the product is not sufficient in ethanol or not enough ethanol is used |
Use more ethanol for elution |
| 21 | Low isolated radiochemical yield (<10%) |
The concentration of the precursor is not sufficient |
The final concentration of the precursor is suggested to be no less than 1 mM. Instead of weighing the HPLC-purified AmBF3 conjugates with a balance, which is not accurate because of contamination (e.g., of TFA salts), we recommend the use of UV absorbance at a certain wavelength (e.g., 277 nm for AMBF3-TATE) to deter- mine the quantity of the AMBF3 conjugates |
| Low isolated radiochemical yield (<10%) |
The pH of the radiolabeling reaction is not suitable |
The final concentration of the pyridazine buffer should be no less than 100 mM |