Chromatography Forum

I am in the planning stages of ordering an Agilent GC for greenhouse gas analysis using headspace injection w/ a Gerstel sampler. We run several hundred samples at a time and I'm looking for a reliable injection septa. Any suggestions or is the merlin acceptable? We will use ECD and FID detectors w/ HS-N and Q columns, and backflush.

Any comments would be greatly appreciated

I've used the Merlin Microseal septum assembly successfully for the last five years. The first seal ran for 13,000 injections but I wasn't monitoring for septum leaks so it should probably have been replaced sooner. The second seal lasted for 3600 injections before it began to leak. The third seal has 1600 plus injections with no leaks so far. It's on an HP 5890 Series II GC with an Agilent autosampler. Keep in mind that you will need a different autosampler syringe, Agilent part #9301-0725. I'm using standard autosampler vials so I can't comment headspace analysis.

I've never had luck using the Merlin for HS analysis. The typical headspace needle (point style 5) tears them up quickly and the merlin compatible needles aren't available for the Gerstel syringes.

I've had good luck with the Supelco ThermoGreen pre-pierced for SPME septa or the Zero Septa from cepure (www.cepure.com).

I've also found that using a older HS needle to line up the prepierced hole with your septa nut is beneficial for life time. I'll typically put these septa in, put a needle through the septa nut and guide the needle through the pre-pierced hole and down into the inlet. Fingrt tighten the septa nut, turn 1/8 turn tighter with a wrench and pull the needle out. Test at 60 psi, if it doesn't hold then tighten another 1/8 of a turn. I've noticed alot less septa particles and cleaner needle travel through the septs when doing this.

Hope this helps