c******m
发帖数: 884 | 1 orotic acid 有3个pKa, 分别是2.78， 9.45, >13.
如果想让 orotic acid 最大程度溶于有机相 (neutralized)，在多大的 pH 值萃取比
较好？是越酸越好吗？
我现在做固相萃取（ion exchange column)，用 2%formic acid/water (pH=2) 洗固相
，结果洗下来许多orotic aicd, 是不是不够酸？还是 pKa2 和 pKa3 在起作用？
Thanks in advance! | s****2
发帖数: 4569 | 2 if it forms TEA salt, say orotic acid.2(3)TEA salts, it readily soluble in
DMF/ACN, even DCM. | c******m
发帖数: 884 | 3 Thank you for the reply. Do you mean triethylamine for TEA? If so, I didnot
use any TEA in the previous wash.
The ion exchange (IX) solid phase (SP) contains a linker-piperazine with pKa
of 6, so I load the orotic acid (ORA, pKa1=2.8) with a pH 4.4 (half of 2.8+
6) solution to make sure both SP and ORA are ionized. Then I use 2%Formic
Acid/water (pH=2) to wash (should not elute any ORA out), and then use NH4OH
in MeOH/ACN to elute ORA. But the result shows the acidic wash step elute a
lot ORA. So I am wondering that the 2%fomic acid may ionize ORA with its
pKa2 or pKa3. But I don't know how.
【在 s****2 的大作中提到】
: if it forms TEA salt, say orotic acid.2(3)TEA salts, it readily soluble in
: DMF/ACN, even DCM.
| s****2
发帖数: 4569 | 4 overlodaing!?
didnot
pKa
8+
NH4OH
a
【在 c******m 的大作中提到】
: Thank you for the reply. Do you mean triethylamine for TEA? If so, I didnot
: use any TEA in the previous wash.
: The ion exchange (IX) solid phase (SP) contains a linker-piperazine with pKa
: of 6, so I load the orotic acid (ORA, pKa1=2.8) with a pH 4.4 (half of 2.8+
: 6) solution to make sure both SP and ORA are ionized. Then I use 2%Formic
: Acid/water (pH=2) to wash (should not elute any ORA out), and then use NH4OH
: in MeOH/ACN to elute ORA. But the result shows the acidic wash step elute a
: lot ORA. So I am wondering that the 2%fomic acid may ionize ORA with its
: pKa2 or pKa3. But I don't know how.
| c******m
发帖数: 884 | 5 Thanks.
I tested the post-loading solution, there is no ORA left in the solution. so
I think it is not because of overloading.
I tried 0.1%formic acid/water (pH 2.7) instead of 2%formic acid/water (pH 2)
to do the wash. This time no ORA is washed out. So I guess the 2%formic
acid may have very high ion concentration that could shorten the ORA
retention. But I am not sure about this hypothesis.
【在 s****2 的大作中提到】
: overlodaing!?
:
: didnot
: pKa
: 8+
: NH4OH
: a
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