I am trying to analysis chloroform in the bulk material as volatile organic impurity.
I use Headspace-GC with FID.
But the problem is the sensitivity of chloroform is too low. As you know, PDE(permitted daily exposure) of chloroform is 60 ug/g. So if I dissolve 1g of bulk material in 10mL DMF, the concentration of solution should be 6 ug/mL.
At that concentration, the peak of chloroform is so small that I cannot believe quantitative analysis.

My GC condition is...
AT-1(0.32 x 30m, 5um)
Oven 35 degree, hold for 9 min ...
(Chloroform detected at 8.0 min)
Carrier gas : 24 psi(He)
HS condition: heat 85 degree, needle and transfer 90 degree...

How can I increase the sensitivity of chloroform?
Please help me...

Dear anonymous,

Please review the following article:

Analytical Chemistry Vol 69 No 11 p2221-2223

Peaks from samples containing chloroform at less than 1ng per vial were detected. At 0.050 µg (50ng) per vial the recovery based on the regression of samples spiked from 0.0005 µg to 1 µg was 99.2%. Methodology is linear up to 100µg per vial and was performed on a Varian Genesis (Tekmar 7000) HS analyzer using an old Varian 3500 GC. Organic solvents such as DMAc or DMF reduce the recovery size by a factor of 3-9 but which remains linear over the range specified. Email me for any questions you may have. You have a lot of chloroform in your sample at 6µg/mL. If you used 1µL of your sample solution then 6ng of CHCl3 would be present in the vial. That is 10 times the amount detected in the above method. You should not have any problems performing this analysis as I am sure you can use more than 1µL of sample per vial for your analysis. Heating time was 6 minutes at 85°C. Sample size was 25 µL. You should optimize your sample at 100 µL, 0.600 µg per vial, per the concentration you stated for maximum peak size.

Rodney George
Supelco R+D
rgeorge@sial.com