Chromatography Forum

Hi there,

I have put in operation ICS900 unit that stood off for few years. Previous operators were determining the rain on it.
On anion unit I cannot detect posphates and sulphates - I can see those peaks but they are stretched over for some 6 mins in concentrations of 50ppm. If I run 10ppm standards, I cannot see them at all.
I'm using AS14 column, AMMC 300 suppressor and eluent is 3.5mM Na2CO3/1mM NaHCO3. The flow is 1.5ml/min and regenerant is 25mN H2SO4. The conductivity of the eluent is 25uS/cm.
I have regenerated the suppressor (250mM H2SO4) and I have put the column the opposite way and put 10 times higher conc of the eluent through it.
By the specs the eluent conductivity should be 16-18uS/cm, and then, hopefully I could resolve the peaks, but I cannot get that low conductivity. Does anybody have any idea how to achieve that low conductivity and why do I get so stretched PO4 and SO4 peaks?
Thanks!

Good Evening,

How old is the AS-14 column that you're using? They will lose functionality even if properly stored after a bit more than two years, as I recall.

Hi Matt,

I'm not sure how old is the column, but it's more than 2 years for sure. Unfortunately, I'm a guest at this institute and cannot influence in buying new column...
Today I have managed to get SO4 ions in conc of 1ppm, but they are stretched and very small. Considering the PO4, I've given up on them... The conductivity is still higher than should be.
Do you happen to know if there's some other way to re-condition the column, beside the 10x higher eluent conc?

Thanks in advance!

Hi Again,

I'm afraid that there isn't any other way that I know of to regenerate the AS-14...or any other IC column. After a time (I've found that it begins at about two years, coincidentally) the functionalities begin to be lost entirely from the resin base material and/or modified and there is little that might be done to remedy that situation...except to buy the new column. Sadly, same will go for the electronic suppressor.

I would recommend trying to use virtual column software (Thermofisher who now owns Dionex) has an online version that free to use here https://appslab.thermofisher.com/Accoun ... lumnOnline

you enter in the type of column, suppressor, eluent, whether it's isoctratic or gradient, and it will demonstrate the best settings for the what your using in terms of peak alignment. might be easier to try that instead of guessing ?

if that doesn't work, I would try new columns and suppressor. I know you are a guest in the lab, but it doesn't help them out either by having this problem.

good luck!

Thanks labmonkey,

I'll try that