Serious problems with Hamilton PRP-X200 column

[PretoriaS]

Hello everyone, my name is Sebastian and I'm a chemist from Argentina. I work in the QC of radio-pharmaceuticals and we are having problems with our method for 11C-Choline. I will try to explain in detail the situation:

We analize the radiochemical purity with a Dionex ICS-3000, with the following conditions:

Column: Hamilton PRP-X200
Mobile phase: HNO3 10mM, prepared with Milli-Q. (We used to use He for degassing, but it has been discontinued by suggestion of a Thermo scientific representative).
Detector: conductivity detector with CSRS4mm suppressor
Standards used: Choline and 2-Dimethylaminoethanol (DMEA)

The systems is showing heavy broad peaks and poor reproducibility. A mix of the two standards can't be resolved. The problem is serious because the previous employee (I started a month ago) had been using these columns for a long time, and as a result there are 3 dead columns in the drawer, in a period of less than 2 years. I started to use a new column but after 3 samples the problems started once again.

I have tried the regeneration proposed by Hamilton (injection of 100 uL of HNO3 1M several times) with no changes. Furthermore I flushed 100 mL of MeOH with HNO3 0.1N with no result. I'm afraid of having definitely killed the column with such harsh conditions.


There is something very wrong that we are doing, but we can't identy what it is and it is frustating. Any help will be more than welcome.


Kind regards,
Sebastian

[tom jupille]

That sort of column (sulfonated polystyrene-divinlybenzene) is generally fairly robust, and your conditions (dilute HNO3) are not particularly harsh. So, some additional questions:

1. If you go ahead and re-test the column using the manufacturer's test procedure (my guess is the test mix would be Li+ / Na+ / NH4+ / K+), how does the column compare to the initial results?
2. What else is in your sample matrix?
3. Go back and look at the records of past column failures. Did the columns deteriorate gradually, or abruptly?
4. If the columns deteriorate gradually, does the deterioration happen if you inject only standards, or only when you inject samples?

[PretoriaS]

Hello Tom, thank you for your reply. I will look into those questions. When I said "harsh conditions" I was talking about the regeneration with methanol-HNO3, because I don't know how much organic solvent this column can handle (0-100% aqueous says Hamilton :S).

I'll add further data when I can.

Regards,
Sebastian

[upamaniah]

it may not be that serious,
remove the column and flush your instrument as well the detector parts.
may be you need to talk to the service eng. for cleaning the instrument.
also mention DMEA is your internal standard?? is that standard mixtures freshly prepared??

[PretoriaS]

I have new information!

I have tried a regeneration protocol with H20-MeOH 90:10/ HNO3 0.1N with no success.

By Tom's suggestion I tried with NH4Cl and NaCl (which appear on the specification of the column) and the results are bad! After washing with H2O-MeOH the baseline is oscillating a lot and the peaks are showing tailing, very long tailing. I flushed the line and even tried an injection of NaCl 100 ppm without the column, to see problems with the injection valve, with the expected result (normal peak at low retention times).

I'm thinking now about physical damage or a blockage in the column as the only option left to explain the problem. Should I try to use the column backwards? (last resort)

Regards,
Sebastian