how much of column to insert inside the detector?

[dipschrom]

Hi. I am a new person on board and am looking for good time with gas chromatography knowledge sharing with all of you. I use a Perkin Elmer Clarus 500 GC with ECD/FID...It would be of real great help if I could get a little direction on the following two things:

1. how much of the column (mm/cm) should I insert inside the ECD detector and FID detector? How much for the injector port?

2. The ECD basline voltage showed >800mv for quite sometime, even though no sample was running. So detached the detector end of the column and baked the detector out at 350 degree C for two days...the voltage came down to 45mV...as per my knowldege ECD voltage without sample running could be around 20mV depending on how old the detctor is..so i continued the baking for two more days and ECD voltage turned 102mV...how to solve this? what can i do to bring the voltage down to ~20mV, when no sample is being analyzed? i use helium as carrier and nitrogen as make-up gas.

thanks,
Dpez

[Fat Jonny]

Do you not have the user's manual?

I have a PE AutoSystemXL GC, which is essentially the same as the Clarus500. My user manual says the column should be inserted into a PSS injector "so the back of the nut is 3.8 to 4.4cm from the end of the column". If you are using on-column injection then obviously your column will fit snugly into the injector liner.

For the detectors, my user manual states that the column should be inserted into the FID detector "so the back of the nut is 70mm from the end of the column" or into an ECD detector "so the back of the nut is 64mm from the end of the column".

With the FID detector you can slide it in while the flame is on and watch down the top of the output, you'll see a glow when the column hits the flame, so pull it a little back so it's not touching.

As for the ECD voltages, I don't use one so can't help with that. But why don't you try running some blanks/standards and take a look at the baseline variation.

[SemiAuto]

I had my first problems with ECD when I tried using other than ultra pure Helium for my carrier gas. Other problems were with using a column that was not designed for 350 degree temp. I was continually bleeding out column phase at that temp. Changing both of these solved my problem.