HELP NEEDED IN VENEZUELA
I am starting to work in a new project related to the determination of polychlorinated biphenyls (congeners) in water by gas chromatography. We have in our lab, an HP 5890 gas chromatograph with an ECD detector, and a wide bore column (HP-608 30 m x 0.53 mm x 0.83mm). W e prepared our first calibration standard of congener no. 194 (an octachloro-bipheny)(accustandard neat) in isooctane (residue grade) in a concentration of 0.020 mg/ml and we did not get a peak in the chromatogram (except for those peaks related to the solvent). Our chromatographic conditions are the following: Inj. Temp.250 °C; Detector temp. 300°C, Oven: Initial temp: 150°C, initial time 0 min; 150-275° @ 5°/min, final time 23 min. Splitless injection 1 ml, purge valve time on 1 min., Column flow (N2) 3,62 ml/min. Detector auxiliary gas (N2) 30 ml/min.
We think that the compound is trapped in the column. What should we do? Increase column flow? Increase the final time? We have tried other temperature programs with the same result.
Thanks, Socorro de Cabré
By anonymous on Wednesday, April 11, 2001 - 04:44 am:
bake the column @300 and see if you see the peak come off. I have run congener's and find this set up is the best: inj 300 det 300 130/0/5/300/18
make you're standard up @ 20 ug/l (PPB) not 20 ppm
that is too high a concentration.
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