Ion exchange column performance??

[rick1112]

Hi

Could some one tell how can I go about doing column performance for Ion exchange columns (Anion and cation)… I am suppose to make a general protocol for Ion exchange column performance for my lab.. a little help plz…

Thanks a lot

[danko]

SST (System Suitability Test) that relates to the method you’re using the column for.

Best Regards

[rick1112]

hi danko,

at this moment i dont have a "SST (System Suitability Test)" as i am in the intial stage of my method development...also i am looking for a general column performance method which can be used for all the Ion exchange column (along with SST where it is avialable..) so i was looking for chemical/Compound for the performance run....?

thanks

[IC_Gal]

We do both cation and anion chromatography where I work. We use the "standard 7" anions mix for our anionic method: F, Cl, NO2, Br, NO3, ortho PO4, and SO4. The "system suitability" criteria we use is threefold
We run a new calibration curve every day and insure that:

1). The column separate all anions with baseline resolution (Rs >/= 1.5) at the highest calibration standard used, in our case 100 ppm.
2). R2 for the calibration curve is >0.99.
3) The response for a midrange or designated QC standard is within 10% of the true value. We also go to a 2nd vendor to get the QC standard.

We've used this protocol for years and have found it gives good results for the types of industrial waters that we test. For cations we use a 6 cation mix of Li, Na, NH4, K, Ca, and Mg with a similar protocol.
We also do check the plates for the midrange standard from time to time to see if the column efficiency is ok.

Hope these suggestions are helpful.
Cheers;
IC_Gal

[rick1112]

hi IC_Gal,
thanks a lot for your reply...
well i am given task to develop a column performance/efficency test for ion exchange column... i went throught COA of some of the columns i presently have (DIONEX Carbopak uses " nitrate" std)..i am looking for a method/compunds which i can uses for all my Ion Exchange column regardless of brand (some thing that works for columns from DIONEX, tosho..or supleco etc..) could you plz help me out..

IC_GAL...
do the ions you use are internally prepared or purchased as standard mixture externally?? could you tell me the method details for such an analysis??
thanks a lot

[IC_Gal]

Hi rick;
We purchase 1000 ppm single anion (or cation) stds that are certified as such. They usually come with a COA that lists the concentration as 1000 ppm +/ 5% or something like that. The anions are simply the sodium salts of the appropriate anion, example sodium chloride, sodium nitrite, sodium nitrate, etc. You can make any anion standard from the sodium salt. Simply insure that the salt is dried in an oven at say 110 deg for a while to drive off the water. Cations are generally chlorides or some other soluble anion salt of the cation.

The seven anions I listed before can generally be used on any ion exchange (anionic) column capable of performing that separation whether they be from Dionex, Metrohm, or whoever. Just insure that the column is intended to perform the desired separation. Construct your calibration curves to bracket the expected concentration of the ions in your samples. Many people make a curve of say 1 - 100 ppm for each anion with 5-7 levels of calibration or points on the curve. Depending upon the capacity of your column you may have to settle for something like 1 - 20 ppm. Some columns cannot separate all of the anions at the higher levels of 100 ppm. The same principles will hold true for the cation method as well.

One note of caution you should know when running IC is that most of the time you are dealing with a conductivity detector. If the sample has too much ionic strength it can overload the detector. One nice rule to keep in mind is that you should never put more than 100 ppm of any anion or cation on the column at a time. This will help you to avoid overloading of the column and bad peak shapes. Dilution of the sample may be necessary and in many cases is recommended. Depending upon your matrix some cleanup steps may have to be performed using solid phase extraction. High levels of organics, surfactants, proteins, etc will foul the column and need to be removed prior to analysis.

[Markus Laeubli, Metrohm]

If the sample has too much ionic strength it can overload the detector.

In most of the cases overloading the detector is not the problem as their ranges go up to 3'000...15'000 µS/cm. But the column might be overloaded.

One nice rule to keep in mind is that you should never put more than 100 ppm of any anion or cation on the column at a time.

Anyway, this role of thumb is a very good guideline.