GC and Helium shortage



we are currently unable to get Helium. We'll run our Helium gas inventory in a few weeks. Between other applications for our facility, it is used as a carrier gas on our GCs for solvent analysis (validated method). I'm copying our method below. Would it be best to use N2 or H2? How do I calculate the equivalent flow. Any other option?

Thanks in advance.


1.1         Injector

Mode: splitless

Temperature: 250 oC

Carrier gas: Helium

1.2         Column

Type: fused silica capillary

Model:  DB-200 (J&W p/n 122-2033),

Nominal Length: 30m

Nominal diameter: 0.25mm

Nominal film thickness: 0.5 µm

Mode: constant pressure, 15 psi.

Nominal initial flow: 1.4 mL/min.

1.3         Detector

Type: FID

Temperature: 300oC

Hydrogen flow: 40 mL/min

Air flow: 350 mL/min

Mode: constant makeup flow

Makeup gas: Nitrogen (30 mL/min)

1.4         Temperature profile

Initial temperature: 40oC for 2 minutes

Ramp:  increased from 40oC to 130oC at a rate of 20oC/min

Ramp time: 4.5 minutes

Post temperature:  maintained at 130oC for 5.5 minutes.

  Total run time:  12 minutes

Parents Reply
  • James,


    I was able to use the same column. I had to reduce the inlet pressure from 15 psi to 11 psi to keep the speed within the recommended range for H2.

    The areas are now 5 times larger (higher sensitivity). The peaks do not resolve at baseline. I'd like to reduce the injection volume from 1 uL to 0.5 uL. The problem is that the autosampler options are 0.2 uL and 1uL. There is nothing in between. Is there any workaround with the chemstation software to inject 0.5 uL with a 10 uL syringe?


    I know that one option is to use 5 uL syringes.   

  • Hi srstrangis,

    The smaller syringe is one way. Depending on the autosampler you have , you may not be able to specify the smaller injection volume without changing syringe to 5ul. You could also stay with the injection volume, but change the method to split . The split ratio would have to be high enough to maintain a recommended total flow of 15 to 20 ml/minute on the inlet. I hope that helps. Let us know what you find.


Was this helpful?