ECD response factors for mix of halogenated hydrocarbons

[kaka_munda]

Hi everybody!

I want to determine the response factors of penta/hexa-chloroethane, PCB101, DDE, mirex and some other chloroalkanes for both FID and ECD. We have a GC with aglient splitter which split streams to both ECD and FID detector. I would like to start with mix and like to use lindane or hexachlorobenzene as internal standard.

Can someone advise me how to begin?

1. Should I make equal molar concentration mix of all above compounds and then dilute them to different levels?
2. Can I use split ratios instead of dilution?

I will be grateful for your valuable input.

Best,
Kaka

[Don_Hilton]

Do dilutions.

Adjusting split to adjust concentration on column is not a good idea to use for quantitation. And if you have the internal standard in the mix it will be split at varying levels also.

YOu can use commerciall available standards which come at convienient levels and then dilute them down to the levels you need. I would not bother to calculate molar ratios. Working with weight per volume solutions works well and is convienient.

[Peter Apps]

Hi Kaka

Bear in mind that the response factors you get will be for the whole system - injector, column and detectors, not just for the detectors themselves. Vaporizing inlets are notorious for discrimination and you have no way of accurately measuring what goes into the column and passes into the detector.

Peter