By Anonymous on Wednesday, June 25, 2003 - 10:17 am:
I am tring to purify a compond which has two -COOH group, one is at side of a C18 fatty acid, another one in at 6 position of a suger which connected to the middle of fatty acid chain by -O- bond.
Because the diol of the same fatty acid can be purified at 4%IPA, 0.1% acetic acid in hexane, UV 202nm r.t =1 0~ 15 min ( normal phase ), I try to purify my compond at 7~20 % IPA, 0.1 % acetic acid in hexane, UV 202nm, but did not get any peak after 1h. ( My compond has 2 more -OH and 1 more -COOH group on the suger comparing to the diol of the same fatty acid )
The PH of mobile phase with 0.1 % AA is ~5, the PK of both -COOH is around 3-4, should I adjust the PH of mobile phase to ~3 by acetic acid ( or by TFA or HCL) ?
Should I adjust the PH of sample to ~3 before injection?
Many Thanks for any suggestion!
By Anonymous on Wednesday, June 25, 2003 - 03:29 pm:
Use 100% IPA with acetic acid, then work backward adding hexane until you got the right retention.
By Anonymous on Thursday, June 26, 2003 - 07:23 am:
Thanks,you mean the compond is more polar than i expected?
I still don't know that I should adjust the PH of mobile phase to < 3 or not.
By Anonymous on Thursday, June 26, 2003 - 03:26 pm:
You are working with IPA and hexane. How are you going to measure the pH?