Chromatography Forum

New to IC in general, and new to the IC/furnace this lab has and am not receiving training. Teaching myself through the manual. Also, it's been 'broken' for the past 1.5 months.

Using a Metrohm Compact 881 Pro IC with a Multitek drive furnace attached as the 'remote box'

We use a 5ppm phosphate scrubber solution, so when a Blank run is done we look for a 5ppm phosphate peak around 13-15 minutes. The machine has been unusable lately because the Blank printouts are terrible - dropping conductivity and background noise and no phosphate peak!

I replaced the older Phosphate scrubber solution with one I made so that I can be sure it was made correctly. I replaced the Eluent aspiration filter. (the eluent used is standard carbonate eluent - the snips from Metrohm). I detected a small air leak between the 'out' eluent degasser port and the high pressure pump, corrected the leak. I purged the valve after changing the eluent aspirator filter to rid the line of any air bubbles.

This has fixed the dropping conductivity, low baseline, and a good bit of noise.
But where oh where is my phosphate peak???????

In November a direct injection calibration was done for the ions we look at: F-, Cl-, and our reference phosphate. I don't believe calibration is the issue. We run the IC at a constant 26C temperature.

What is the baseline conductivity you are seeing now?

Wondering if you are loosing the peak in the baseline noise.

Ours usually runs around 1uS or below.

Dear darlela

Missing phosphate peaks are often a result of iron contamination in the system (inline filter, precolumn, column, MSM). Iron is usually introduced with the eluent over time as the respective chemicals as they typically contain traces or ultratraces if iron.

Did you change the "Inline filter", Guard column, and/or the column?

Please send me a "typical" chromatogram (*.idet) for inspection (markus.laeubli@metrohm.com) and contact your local Metrohm serviceperson.

Best regards
Markus

What is the baseline conductivity you are seeing now?

Wondering if you are loosing the peak in the baseline noise.

Ours usually runs around 1uS or below.

Hi, I attached an image of the readout. Our baseline is relatively clear and around 0.93us

What is the baseline conductivity you are seeing now?

Wondering if you are loosing the peak in the baseline noise.

Ours usually runs around 1uS or below.

Hi, I attached an image of the readout. Our baseline is relatively clear and around 0.93us

That is good, I have seen on our instruments if the degasser before the detector stops working the background conductivity can rise and hide smaller peaks like phosphate. Also as above if the precolumn(guardcolumn) or column becomes contaminated with iron it can broaded the peak so much that it is lost.

It may be time for a new guard column or new analytical column if they have become contaminated.