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EJNMMI Research

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 efficiencyc

TLC conversion

HPLC purity

[18F]11 yieldd

Ethanol:pivalonitrile:veratrole (1:4:4)

42%

85%

90%

32%

Ethanol:acetonitrile:DMSO (1:4:4)

69%

75%

80%

41%

Veratrole

30%

85%

61%

16%

Pivalonitrile

35%

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)a

100% (no cartridge)

92%

91%

84%

Methanol:veratrole (1:3)

90%

94%

97%

82%

Methanol + veratrole:pivalonitrile (1:1)b

93% (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)
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