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Re: Benzene/Toluene in water: what internal standard?
Posted: Sat Apr 04, 2015 5:17 pm
by dblux_
...
Extraction: I'll centrifuge water and benzene+solvent at 600 rpm for 15 minutes,...
You need rather to shake it vigorously. Emulsion will easily disapear forming two layers when you stop shaking.
I'll put the vial at 4 degrees and when the vial reach the 4 degrees I take out 0.5 microliters of solvent+benzene with a syringe, I fill the other 0.5 microliters of the syringe with solvent + internal standard and I inject in the GC.This procedure is to reduce volatilisation and to know the partition of benzene between water and solvent.
Execute your experiment in room temperature
Is it a good way? How know the partition?
The GC column is capillary, non polar, suitable for aromatics and pesticides. Phase: bonded; poly(5%diphenil/95%dimethylsiloxane). I'd like to know if the substances mentioned above are dangerous for the column and how set this program in the best way:
Hydrogen 30 ml/min (fixed)
Air 300 ml/min (fixed)
Carrier gas: He 1 mL/min
Detector temperature: 180°C or 250?
Injector temperature: 180°C 250 or 250?
Oven temperature program: I know three program used with other column to determinate BTX, but I need to identify only benzene. Really ? Forgot about internal standard ?What is the best program?
35°C for 5min , to 70 °C at 5 C/min, to 180°C at 15C/min and hold 10 minutes at 180°C
50°C holding time 1 min, to 70°C at 5/min, to 200 at 20 °C/min and holding 200°C for 20 min
40°C for 5 min, to 48°C at 2 C/min and to 120 at 15 °C/min (no holding time at 120°C)
Injection: splitless. Why ?????????
Thanks!
Andrea
Re: Benzene/Toluene in water: what internal standard?
Posted: Sat Apr 04, 2015 5:44 pm
by RobinDelBosco
Hi dBlux,
ok only shake, without centrifuge.
room temperature: benzene and solvent are volatile, so your advice is .. do as faster as I can?
injection: Correct, I don't forget internal standard. But at the moment I don't know what is better, ethylbenzene in hexane or dichlobenzene in dichloromethane.
What oven program and type of injection do you advice me?
Thank you
Re: Benzene/Toluene in water: what internal standard?
Posted: Sat Apr 04, 2015 10:42 pm
by dblux_
Hi dBlux,
ok only shake, without centrifuge.
room temperature: benzene and solvent are volatile, so your advice is .. do as faster as I can? 5 to 10 seconds is enough time to withdraw organic layer, amount of volatiles you loose in 5 seconds is negligible. Besides, that's (among other reasons) why you use internal standard - to compensate for volatiles lost
injection: Correct, I don't forget internal standard. But at the moment I don't know what is better, ethylbenzene in hexane or dichlobenzene in dichloromethane.
What oven program and type of injection do you advice me? Start with split. You have very simple mixture to resolve and you may check which program is sufficient. Probably you will be able to shorten each of the programs because you don't have high boiling compounds
Thank you
Re: Benzene/Toluene in water: what internal standard?
Posted: Sun Apr 05, 2015 2:50 am
by RobinDelBosco
Dear all, thanks for your help.
Dear Dblux,
many thanks
Re: Benzene/Toluene in water: what internal standard?
Posted: Sun Apr 05, 2015 7:10 am
by dblux_
Let us know in the future about the outcome of your experiments. Spend a nice time with chromatography
Re: Benzene/Toluene in water: what internal standard?
Posted: Sun Apr 05, 2015 7:33 am
by Peter Apps
room temperature: benzene and solvent are volatile, so your advice is .. do as faster as I can?
Thank you
Use a septum-capped vial, and withdraw sample though the septum.
Peter