SPE preparation waste water

[willemdm]

I'm trying to find an SPE method for the analysis of organophosphor and organochloride pesticides in wastewater.

currently i'm using Oasis HLB column with following method:

1) wash column with DCM, ACN and water
2) load sample
3) wash with 30% MeOH in water
4) dry for 30 minutes
5) elute with DCM
6) inject with Large-volume injection on GC/MS (single quad)

this method works for drinking water,... but for wastewater i still have a lot of coeluting peaks. there is still a lack of selectivity...

any help to improve this method?
.

[Don Shelly]

Use a hydrophobic DVB (500 mg bed/L of sample). It will be more selective. Are you using SIM?

Don