Chromatography Forum

Hello,

I am currently trying to determine a good sample concentration and split ratio for a GC method using a FID detector. Is there a peak height (milivolts)considered desirable with a GC-FID detector?

I know in HPLC a peak height around 1 AU is considered an appropriate height for accurate determinations. Is there a GC-FID version of this rule of thumb?

Thanks

James

GC differs from HPLC in the linearity of detection for the most common detector.

FID for most manufacturers is linear over a range of about six to seven orders of magnititude. HPLC UV detection is linear over a smaller range. Thus, the FID amplifier setting can and will be changed if conditions require it.

Measuring a peak which reaches the 1volt limit will require a split higher than a peak which is close to the detection limit which may require a splitless injection.

A peak having a height half the dynamic range of the amplifier should be measured accurately. Adjust your concentration and volume and split so this can be reached if conditions permit it.

I hope these meager comments help your understanding of the situation.

best wishes,

Rod

I know in HPLC a peak height around 1 AU is considered an appropriate height for accurate determinations.

1 AU is pretty darn large !!!! We usually stay under 100 mAU with today's better instrumentation.

I agree. Historically, getting near the 1 AU limit is out of linear range.

But one question at a time, right?

best wishes,

Rod

Thanks for your help Rod. I understand the situation a bit better now.

James