Problems with IC PAK Anion HC column

[Rodolfo10121970]

Greetings,

I have had problems with IC PAK Anion HC column.
After several injections, my target begins to "walk" during the injection or after it had been set up for the firt time, my target do not "appers".
I followed all the procedures that the column manual discribed, but with out success.
Where can I found more informations about this column behavior?
Att,
Rodolfo

[Markus Laeubli, Metrohm]

without information about sample and ion of interest, nobody will be able make a suggestion.

[Rodolfo10121970]

Greattings,

My apologies, my fault.
I am working with Pamidronate Disodium.
I'm making tests with the method of U.S. Pharmacopoeia 35 Official Monographs page 4200 (Assay).

"Mobile phase— To 2500 mL of water, add 0.47 mL of anhydrous formic acid, adjust with 2 N sodium hydroxide solution to a pH of 3.5, filter, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621). [note—The small amounts of formic acid have a strong influence on the retention times. ]
Standard preparation— Dissolve an accurately weighed quantity of USP Pamidronate Disodium RS in water, and dilute quantitatively, and stepwise if necessary, with water to obtain a solution having a known concentration of about 2 mg per mL. Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a refractive index detector and a 4.6-mm ×10-cm column that contains packing L23. The flow rate is about 1.0 mL per minute. The column temperature is maintained at 35. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the tailing factor is not less than 0.3 and not more than 1.2; and the relative standard deviation for replicate injections is not more than 2.0%."

Att,
Rodolfo

[Markus Laeubli, Metrohm]

Do you mean the Pamidronate peak was shifting to shorter or longer retention times?
Is the pH of the eluent constant?

[Rodolfo10121970]

Greattings Markus,

The pH of eluent is constant.
The Pamidronate peak had had both behaviors after 50 injectons.
But some columns after setup and after few injectons showed that Pamidronate peak did not interection with it.
So I have columns that has a short life time and columns that I do not get the Pamidronate peak.
Thanks for your helpping.
Att,
Rodolfo

[Markus Laeubli, Metrohm]

Dear Rodolfo

Unfortunately the behavior is not consitant. Therefore I assume that this is more a column problem. I would recommend to check back with your Waters representative for further information.

[Rodolfo10121970]

Dear Markus,

Thanks a lot.
I already had asked for futher information but the Waters representative did not ansewered yet.
I will post it.
Att,
Rodolfo