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- Posts: 185
- Joined: Fri Jul 20, 2012 9:18 am
Hello,
For the analysis of both pesticides and PAH's we are using a single liq-liq extraction using CH2Cl2 as extraction solvent.
10ml of CH2Cl2 is added to 150ml of sample in a 150ml Duran bottle. This is put on an agitator for 5 min. The solvent can than be easily transferd to a test tube by using a glass serological pipette. The solvent is than dried by adding Na2SO4 and vortexing. After centrifugation 1ml of the dried solvent is transferd into 2 separate vials to be analysed on a Thermo Trace GC - TSQ for pesticides and on an agilent 7890a -QQQ for PAHs.
on Thermo:
50µL CH2Cl2 at once injection on a large volume liner with sintered glass beads.
max. PTV temp: 320°C for 20 min
On Agilent:
50µl CH2Cl2 speed controled on a glass-beads + glass wool liner
max. PTV temp: 300°C for 5min
Both systems have a 5m siltek deactivated pre-column.
Problem is that both systems are being troubled by rapid loss of inertion. On Thermo we can perform about 200-250 injections (= about 3-4 runs) before changing the pre-column (liner will last about 100 inj), on Agilent it takes only 5-10 injections to ruin the liner and cause bad chromatografical separation of critical compounds.
As a drinking water company we are mainly testing tabwater and ground water. The amount of surface water is a lot smaller and most of these are fairly clean. So this should not stress the system to much.
* Is in your opion the CH2Cl2 to blame for the rapid loss of inertion? We are injecting 50µl but of course most of the solvent is blown off through the split-valve.
* Is there an other GC-compatible solvent suited for extracting both pesticides and PAH? (extra difficulty is the lack of air-conditioning in our lab. Temp can rise up to 30°c )
I hope you can help us.
Kind regards
BMU
For the analysis of both pesticides and PAH's we are using a single liq-liq extraction using CH2Cl2 as extraction solvent.
10ml of CH2Cl2 is added to 150ml of sample in a 150ml Duran bottle. This is put on an agitator for 5 min. The solvent can than be easily transferd to a test tube by using a glass serological pipette. The solvent is than dried by adding Na2SO4 and vortexing. After centrifugation 1ml of the dried solvent is transferd into 2 separate vials to be analysed on a Thermo Trace GC - TSQ for pesticides and on an agilent 7890a -QQQ for PAHs.
on Thermo:
50µL CH2Cl2 at once injection on a large volume liner with sintered glass beads.
max. PTV temp: 320°C for 20 min
On Agilent:
50µl CH2Cl2 speed controled on a glass-beads + glass wool liner
max. PTV temp: 300°C for 5min
Both systems have a 5m siltek deactivated pre-column.
Problem is that both systems are being troubled by rapid loss of inertion. On Thermo we can perform about 200-250 injections (= about 3-4 runs) before changing the pre-column (liner will last about 100 inj), on Agilent it takes only 5-10 injections to ruin the liner and cause bad chromatografical separation of critical compounds.
As a drinking water company we are mainly testing tabwater and ground water. The amount of surface water is a lot smaller and most of these are fairly clean. So this should not stress the system to much.
* Is in your opion the CH2Cl2 to blame for the rapid loss of inertion? We are injecting 50µl but of course most of the solvent is blown off through the split-valve.
* Is there an other GC-compatible solvent suited for extracting both pesticides and PAH? (extra difficulty is the lack of air-conditioning in our lab. Temp can rise up to 30°c )
I hope you can help us.
Kind regards
BMU
