Chromatography Forum

Im using Agilent 7890b GC with DFPD detector. Using The checkout method given in Agilent user manual.
Column: Agilent 19091J-413, HP1,
30.0 m × 320 μm × 0.25 μm.
The sample is methylparathion.
The flame is on, output is around -1.4 and output 2 reads around 2.4.
Run time is 15min.
But not getting any peaks.Can someone help ???

Are you sure that the standard is ok? Try injecting some dimethylsulfide vapor with a gas-tight syringe. DMS elutes early so you'll know if you're making progress quickly. It stinks so keep it in the hood!

Thank you for that. But the sample being used now was used previously and had given the peak. I'm not sure if the DFPD is igniting. The hardware panel though says as Flame ON. I think so coz, im not able to see any vapours getting collected. Also the hardware panel shows a negative output, though output2 is positive.

Can you use the "old fashioned mirror test"? You can check for ignition of an FID by holding a shiny piece of metal or a watch glass over it to check for condensation. Water will condense on the watch glass if the flame is lit.

sjv,

I am assuming you mean a PFPD? If so, you should hear the pop, pop, pop of the detector it is working normally. If you don't hear that I would first look to see if the ignitor is working and then check the flows to make sure they are where they should be.

Best regards,

AICMM

sjv,

As soon as I hit post, I realized you may be talking about a dual flame FPD. If so, yes you should see water collecting in the jar, otherwise you are not lit. On a regular FPD (at least in sulfur mode) the zero is around 500 or so and relatively "noisy" so if you don't see a significant flicker I would argue you are not lit.

Sorry about my misunderstanding.

Best regards,

AICMM

Thank you all for the help. That's quite encouraging.
Ur right, I am using a Dual Flame Photometric detector. But I am not seeing any vapours getting collected. On running the gc with the vent tube removed, able to get something that looks like a peak. On exporting this raw data to another project there is an area mismatch. Not sure of wat is going on.

regards
sjv

sjv.

When you say vent tube, you mean the rubber tube or the metal tube with fitting? If metal tube, you are allowing ambient light into the detector so not advised. This may be your stray peak.

I assume you are running rather rich as well in order to obtain some sulfur sensitivity?

Try something for me. Put the rubber tube back on, tell the detector flame off, then tell the detector flame on again. Pinch the rubber tube about 3/4's closed with you thumb and forefinger. Wait till you feel the pop, wait till your detector drops the air flow down to the operating level then let go of the rubber tube. Zero should be pretty high (hundreds....)

Best regards,

AICMM