large standard deviation for my Aglient 6890 GC

[biomass]

Dear all,

Recently, I just switch from GC/MS to GC/FID (Agilent GC 6890N), but I found my peak reproducibility decreased a lot.


My interested peaks are methanol (Peak height is around 40 pA), phenol (Peak height is around 1000pA) and 1,6-anhydro-?-d-glucose (Peak height is around 40pA). I found these peak area standard deviation changed from 4% to 13%.

My GC parameters are:
Injector: 275 degree C; split ratio 10:1

Column flow: constant flow: 1ml/min.
Column: VF-1701ms (ID 0.25mm)

Oven temperature: temperature programming. And the maximum analysis temperature I set is 250 degree C.

FID detector:
temperature: 250 degree C;
H2 flow: 40ml/min;
Air flow: 460 ml/min;
Make up gas flow: 25ml/min.

Can you tell me what's the problem and what can I do to improve my system.

[soccerdad007]

Lots of potential solutions.

I would start at the beginning with the injector and the syringe but someone once told me (& this is correct a lot of the time) that most problems are solved by looking at the inlet
Some possibilities
Is the correct liner being used?
Is it clean?
Is the septum leaking?
Is the gold seal contaminated.
Is the column connected properly.

Just a start
Kevin