Common problems	Potential reasons and solutions
[18F]fluoride is not efficiently eluted from the QMA	· TBA-HCO3 was not prepared correctly. Ensure the concentration is adequate.
· There are leaks on the TBA-HCO3 vial. Make sure the crimp seal is tight and the septum is not pierced prior to installing it on the IFP.
· TBA-HCO3 is not in good condition. Order a fresh batch.
Labeling yield is low	· There is moisture in the precursor solution. Dry precursor and solvents.
· Temperature is too low.
Reaction solution is yellow	· The product is decomposing due to base. Use less TBA-HCO3.
· There is too much precursor. Use less precursor.
· There is too little solvent for the amount of 18F-. Use more solvent.
Additional peaks on radioHPLC	· Nitro group is being substituted: reduce the reaction temperature or shorten reaction time.
Hydrogenation reaction does not work	· Catalyst is not good. Use a new cartridge.
· Flow is too fast and does not allow sufficient contact between catalyst and substrate. Decrease flow.
· Hydrogen pressure is too low. Increase H2 pressure.
Hydrogen pressure increases dramatically during procedure	· Cartridge integrity is compromised and solid support is clogging the lines. Stop the flow and shut off the gas. Let radioactivity decay. Remove catalyst cartridge and flush the system. Put a new cartridge.
Hydrogenation yield is low	· Too many impurities competing for the catalyst (MeCN, oxalic acid). Decrease amount of impurities or increase mass of precursor (Warning: increasing precursor amount will reduce specific activity).
Recovery of radioactivity from hydrogenation step is low	· There is a leak in the system. Check for leaks and backflush into the hydrogen line.
· Compound is defluorinating in the reactor. Evaluate different reaction conditions (pressure, temperature, flow, etc.).
Too much radioactivity is lost during filtration	· Wet the filter prior to use.
· Use filter with a lower dead volume.
The final product peak on the HPLC looks broad	· Too much volume injected. Inject lower amount. Use column with larger diameter.
· The column is not well conditioned. Condition the column for at least 30 column volumes.
· pH of the mobile phase is low. Make sure that the pH ≥ 8.
· Column is not in good condition. Replace column. Use column compatible with basic pH.