lgchrom wrote:
There is mostly loss of resolution in the early eluting peaks. The divalent ones elute more than 15-20% earlier. What do you think?
Assuming that the system works perfectly with another IC column, I would open the column inlet to see if there is frit contamination and/or void has developed at the head of the column and the guard column. This can also be tested by reversing the column direction (the frits are identical on both ends so no worries about reversing the directions for a short time).
Even a small void is enough to degrade the resolution of early eluting peaks. The decrease in the retention time of the divalents indicates there is some loss of capacity but it is not that drastic. The early eluting peaks are more affected by the hardware issues (such as contaminated guards/ voids at column heads/ extra long tubings before and after the column/ column overload - the most ignored aspect)
Try a fresh carbonate eluent after 0.1 M HCl and 0.1 M Na2CO3 washes. Hope that works.