Chromatography Forum

Hi All,

The background signal of my 5890 FID is now just 0-0.3 on the panel. it used to be around 15 even till yesterday. And it now has very low sensitivity. I tried to directly inject 3 ul methanol, the peak height is less than 10 mv.
This instrument was working perfectly until this morning. I was analyse alcohol in water solution. I read some post saying that water could cause problems for FID, but it looks my situation is different from theirs.
Does anyone know what is the problem with my FID?
Thanks!

Hai,

Sensitivity going down may be due to many reasons.

1. Have you checked the Hydrogen and air ratio flowing into fid. The H2 and air cylinders must be near empty, change cylinder and check
2. Also it may be due to leakage of H2 or air at the detector end, or below the jet. - Check leakage .

3. There may be a block in the jet.

4, Remove the column, cut a lit bit and fit again.

5. Possibility of electrometer also not working. turn on your data processor, swithc off the fid electrometer and again switch on there must be change in the baseline. if there is a change in base line, your electrometer is ok. if not your electormeter is faulty.

Vajjara

I bet your jet or fid is plugged with graphite, did you change columns recently?

Could be a simple as tightening the column detector nut.
Is the make up gas on?

Also as above... clean detector, check flows etc.

On my 5890 when I get a signal of 0.3 my flame is out.