Metrohm 940 Vario - Sulfate in ICE column

[Eluent123]

Hello All,

I am in the process of qualifying a new instrument, a Metrohm 940 Vario IC with a 858 sample processor. The material to be analyzed using this instrument will primarily be hydrofluoric acid (about 50% strength HF but diluted during sample prep).

The issue I am running into is we utilize a Dionex ICE AS6 column to prevent fluoride overloading. The anions of interest here are chloride, nitrate, phosphate, and sulfate. We expected that the AS6 based on its material and storage before use to have to flush out some sulfate. Discussing with our Metrohm reps they suggested just running several water blanks to rinse it out (18.2 megaohm).

I've done this and based on the chromatograms, the sulfate peak doesn't seem to diminish.

Are there other suggestions in flushing out this sulfate? The AS6 is brand new.

Other details:
500 mM H2SO4 suppressor
Eluent is 3.2 mM Na2CO3, 1.0 mM NaHCO3
water reservoir and dosino reservoir uses 18.2 DI water.

thanks in advance.

[Nadine Seifert, MIHQ]

I would suggest to rinse the column overnight to see if the sulfate decreases then.

Kind regards
Nadine

[anionman]

Turn the eluant concentration up and run blanks that way. I have a new Integrion that is only 18 months old and it has a persistent chloride peak that is very hard to eliminate. If I run enough blanks it goes away but when a high Cl sample gets run or even a high level calibrator it comes back. It is well below the reporting limit so I don't worry about it.