Chromatography Forum

We often have samples of waste water or leachates that have super high levels of humic acids that interfere with almost the entire chromatogram. Does anyone know of a way other than GPC to remove these compounds without losing the base, neutral and acid target analytes for a normal Semivolatiles run?

I have used silica gel before when analyzing PAH samples but not sure if it would remove all the acidic phenols from the full list. Likewise with Fluorosil.

As it is we sometimes need to dilute 10x or more to have good recovery on the internal standards but that can put a client out of compliance on their permits since the detection limit exceeds their regulatory limit. If only regulators understood that not all samples are as clean as DI water and not expect the same detection limits for everything.

I did a little googling of "humate extraction". It sounds like sodium hydroxide is used to solubilize humates with acid groups from lignite and soil and then they precipitate these humates with acid. Perhaps you can acidify and centrifuge or filter out humates without loosing the 8270/625 analytes?

Two links were interesting to me....
https://humates.com/pdf/ORGANICMATTERPettit.pdf

Here is a commercial source of humates...
https://www.humates.com/mvh-lp1.html?gc ... gKZvfD_BwE

I did a little googling of "humate extraction". It sounds like sodium hydroxide is used to solubilize humates with acid groups from lignite and soil and then they precipitate these humates with acid. Perhaps you can acidify and centrifuge or filter out humates without loosing the 8270/625 analytes?

Two links were interesting to me....
https://humates.com/pdf/ORGANICMATTERPettit.pdf

Here is a commercial source of humates...
https://www.humates.com/mvh-lp1.html?gc ... gKZvfD_BwE

I wonder if that would remove the Benzoic Acid target analyte?

The butanoic, hexanoic, ect acids are always a pain, causing small retention time shifts and sometimes loss of active bases like Benzidine.

Currently running a 5:1 split injection, before when it was splitless it would knock out a column pretty fast.

I've not done 8270 since 1992 and only Pest, PCB by GC-ECD. I wonder if one of the new SPE filters would trap the humates or if they would just come back off when you recovered from the filter.

What about ion exchange resin? DuPont Amberlite SCAV3 Cl is supposed to be selective for high molecular wt organic molecules and specifically humates in cleaning up process water. Might just clean up all your analytes too.