GC/FID TPH (C10-C40) Baseline Shift Problem

[la_donz27]

Hi, Qazedc;

I think Peter & Hornet are right on the money - the first thing to do is change that 6-year old trap.

If you get oxygen inside the column, then elevate the column oven temperature like you're doing each run, you will definitely badly damage the column phase, resulting in high bleed.

Try that first, see how an injection looks after that, but you might just be stuck replacing the column anyhow if the phase is already damaged.

Best of luck!

Donna

[qazedc]

Hi,
To Davide & Donna
Firstly thx for the information about the columns and the ferrules.
i will get the trap in 2 days and will see what will change.

i made a sequence for TPH calibration curve at 6 different points in the weekend and attached below 2 concentrations of the chromatograms and the method using “subtract blank run”
20ppm TPH

500ppm TPH

The correlation of the calibration curve is 0.99918 and there is hill too

- If i dont understand wrong, you do not give an quantitative result below lowest calibration point.
Here is Agilent 6890N and it supports pulsed splitless but the installed liner is split where the link is:
http://www.agilent.com/store/productDet ... =5183-4647
can i run splitless mode with this liner?

Thx both of you for your consideration.

[Hornet]

Restek cod. 23303 (top quality)
Restek cod. 22405 (cheaper and works ok for this application)
Agilent cod. 5062-3587 (agilent equivalent)

Your is wide and tapered, but has the wool in a bad position for splitless analysis plus it has a neck in the middle.

[qazedc]

Hi

Yes i know the agilent 5062-3587 but the main problem for me that i do not run only the analyses of TPH, there are many other methods (like BTEX, PAH etc.) run with this.

if i use splitless liner like agilent 5062-3587 at that case will have problem for the other analysis (all are split mode).

it seems that i will use "subtract blank" method for TPH, at least till get a new column. Baseline is barely stable (but success) after 1 hour column condition and 4 blank injection. i think ambient temerature differences effects it too.


Thx again.