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Table 2 Influence of the solvent system in the synthesis (without eluent additives) of the intermediate product [18F]11

From: [18F]Atorvastatin: synthesis of a potential molecular imaging tool for the assessment of statin-related mechanisms of action

Solvent (400 μL)Elution efficiencycTLC conversionHPLC purity[18F]11 yieldd
Ethanol:pivalonitrile:veratrole (1:4:4)42%85%90%32%
Ethanol:acetonitrile:DMSO (1:4:4)69%75%80%41%
Veratrole30%85%61%16%
Pivalonitrile35%80%63%18%
Dimethyl sulfoxide (DMSO)57%68%64%25%
Methanol:DMSO (1:2)86%64%72%40%
Methanol:DMSO (1:3)86%95%92%75%
Methanol:DMSO (1:3.5)85%86%87%64%
Methanol:DMSO (1:7)65%55%90%32%
Butanol:DMSO (1:2)50%20%23%2%
Butanol:DMSO (1:3)54%80%79%34%
Ethanol:DMSO (1:3.5)70%78%78%43%
Water:DMSO (1:17)36%85%83%25%
Aqueous [18F]fluoride:DMSO (3:97)a100% (no cartridge)92%91%84%
Methanol:veratrole (1:3)90%94%97%82%
Methanol + veratrole:pivalonitrile (1:1)b93% (56%)85%94%74% (45%)
  1. a30 μL of aqueous [18F]fluoride was directly added (no elution cartridge needed) to the DMSO solution containing 8 and 13 and left to react
  2. b300 μL of methanol was used to dissolve 8 and 13 to elute the cartridge. Methanol was then evaporated, and the solvent exchanged to 400 μL of veratrole:pivalonitrile (1:1 v:v) for the reaction. This method, despite having high elution efficiency (93%), showed significant losses (up to 45%) of the eluted [18F]fluoride during the evaporation of methanol. Thus, the real efficiency and [18F]11 yield is shown in brackets
  3. cCalculated by the ratio between the [18F]fluoride trapped in the anion exchange cartridge (45-PS-HCO3) and the radioactivity recovered (without reversing the cartridge) in the reaction vial
  4. dNon-isolated 18F-deoxyfluorination yield based on radio-TLC and radio-HPLC analysis of the crude product and having in consideration the elution efficiency resulting from the solvent mixture used in relation to the starting radioactivity. The final percentage of [18F]11 yield was determined by multiplying the elution efficiency with radio-TLC conversion of the starting [18F]fluoride and with radio-HPLC purity (n ≥ 2)