Table 2. Radiolabeling of Precursor 2 in MeCN at 120°C and 5 min Reaction Time with Bu4NOMs Elution (20 mM in 1 mL of 50% MeCN/H2O) Using Different Preconditioning of the QMA.
| screening
of different preconditioning anions for
elution by Bu4NOMs | ||||
|---|---|---|---|---|
| preconditioning anion | pKa35 | EE (%) | RCC (%) | pRCY (%) |
| Cl– | –7.0 | 24 | 0 | 0 |
| OMs– | –1.9 | 28 | 0 | 0 |
| SO42– | 2.0 (−9.0)a | 96 | 0 | 0 |
| H2PO4– | 2.1 | 86b | 0 | 0 |
| C2O42– | 4.2 (1.3)a | 99 | traces | traces |
| AcO– | 4.7 | 45 | traces | traces |
| HCO3– | 6.4 | 91.0 ± 5.4c | 56.7 ± 8.9c | 52.1 ± 6.9c |
| HPO42– | 7.2 | 95.6 ± 0.9c | 53.4 ± 4.3c | 51.0 ± 5.4c |
| CO32– | 10.3 | 92.0 ± 6.3c | 55.1 ± 1.1c | 50.7 ± 4.3c |
| PO43– | 12.7 | 97.0 ± 0c | 74.3 ± 14.2c | 72.0 ± 11.3c |
a
pKa for second protonation if only one of the divalent anion was investigated.
b
Higher elution could be due to a mixture of mono- and divalent anions formed in aqueous solution.
c
Reactions carried out in triplicates.