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- Posts: 515
- Joined: Fri Jun 02, 2017 11:10 pm
- Location: Western Colorado
First some preliminary backstory...
A while back, we had a sample that was activated carbon pellets from a refinery. They wanted 8260VOC before disposal. Of course putting pellet in a VOA and doing P&T 8260 resulted in loss of the internal standards and surrogates (ISS). I tried sonication, no go. I did a little reading and came across a paper that talked about methanol displacing what was absorbed. I treated it like a high VOC soil and sonicated 10g of pellets with 10 grams of MeOH. This worked at least to the extent that I was able to report VOC's that had been in the pellets.
Now we are getting groundwater that has been sampled from sites that have had injections of activated carbon to try and reduce BTEX. Centrifuging helps but often the only solution to fine carbon dispersed in the VOA vial is to dilute the sample which decreases the loss of ISS added in sample prep.
Recently I've been running samples by 8260 SIM that necessarily need much lower ISS to properly work with very low levels of analytes. This exacerbates the loss of ISS when activated carbon is present. I know from experience that up to 100uL of MeOH extract can be taken from a soil-MeOH extraction and combined in a 5mL syringe with ISS to prep a sample for P&T 8260VOC analysis without affecting chromatography or spike recovery.
So, to cope with dissolved activated carbon in groundwater.
1) centrifuge the pair of sample vials to reduce particles suspended in the water.
2) Add 100uL of MeOH to your empty P&T autosampler vial.
3)Draw up your sample in a 5mL syringe, add ISS, and transfer to a 40mL P&T vial.
Note: You can add the MeOH to the 5mL syringe during each sample prep but I found it easier to prep several vials with MeOH before hand.
4)Take the sealed 40mL P&T vial and sonicate for 5-10 minutes.
Note: This helps the MeOH get absorbed into the activated carbon and thus prevents absorption of ISS by the activated carbon. My guess is that this floods the activated carbon with the MeOH.
5)Run the sample as per method.
Let me know if you have a similar work around.
A while back, we had a sample that was activated carbon pellets from a refinery. They wanted 8260VOC before disposal. Of course putting pellet in a VOA and doing P&T 8260 resulted in loss of the internal standards and surrogates (ISS). I tried sonication, no go. I did a little reading and came across a paper that talked about methanol displacing what was absorbed. I treated it like a high VOC soil and sonicated 10g of pellets with 10 grams of MeOH. This worked at least to the extent that I was able to report VOC's that had been in the pellets.
Now we are getting groundwater that has been sampled from sites that have had injections of activated carbon to try and reduce BTEX. Centrifuging helps but often the only solution to fine carbon dispersed in the VOA vial is to dilute the sample which decreases the loss of ISS added in sample prep.
Recently I've been running samples by 8260 SIM that necessarily need much lower ISS to properly work with very low levels of analytes. This exacerbates the loss of ISS when activated carbon is present. I know from experience that up to 100uL of MeOH extract can be taken from a soil-MeOH extraction and combined in a 5mL syringe with ISS to prep a sample for P&T 8260VOC analysis without affecting chromatography or spike recovery.
So, to cope with dissolved activated carbon in groundwater.
1) centrifuge the pair of sample vials to reduce particles suspended in the water.
2) Add 100uL of MeOH to your empty P&T autosampler vial.
3)Draw up your sample in a 5mL syringe, add ISS, and transfer to a 40mL P&T vial.
Note: You can add the MeOH to the 5mL syringe during each sample prep but I found it easier to prep several vials with MeOH before hand.
4)Take the sealed 40mL P&T vial and sonicate for 5-10 minutes.
Note: This helps the MeOH get absorbed into the activated carbon and thus prevents absorption of ISS by the activated carbon. My guess is that this floods the activated carbon with the MeOH.
5)Run the sample as per method.
Let me know if you have a similar work around.
