Chromatography Forum

Hello, to start sorry for my bad English, I am French, but I will try to be most clearly possible.

Terms:
- 40°C, 5°C/min => 240°C (40mn)
- Column dB-Wax 30m*0.32mm*0.5µm
- H2 0.8mL/min, constant Pressure 29.09
- FID detector
- Time of incubation of the samples: 180mn

Software:
Management Frontier runner: Maestro
Aquisition management: Ezchrome

I have a problem with my GC, I work in Headspace and when I launch my sequence of 25 samples (26h ~ of run) my device incubates my sample N°6 ad infinitum (the 5 first did not have any problem in the injection and the aquisition).

Do you have an idea of why? I wanted to look at if there were a “Run Prep” but I read that it was automatic.

Thank you in advance

Sometimes, when a new sample has to be loaded into the headspace oven at the same time as a sample is being injected to the GC the whole system freezes. Try reducing or increasing the incubation time by two minutes to avoid this clash.

Two comments on your method; do you really need such a long incubation time ? and your carrier gas flow rate is much too slow - you will get better separations in less time if you use 2 ml/min.

Peter

Ok I will try to start again the sequence by changing the time of incubation of one or two minutes. I would tell you if it goes better

For my method, I work on the analysis of the headspace of a wine of synthesis, my time of incubation was determined compared to the moment when I am with balance, it is my optimal time of incubation.

For my flow, I must be with a swiftness of 37.2cm/sec with constant flow, if it is higher I have besides Co-elutions in my spectrum.

The linear flow that you are aiming at is for helium. For hydrogen the optimum is 50 cm/sec. I think that you need to check your flow anyway - given your inlet pressure at your starting temperature your volume flow is about 1.6 ml/min, which gives a linear velocity of 31.4 cm/s. If your volume flow really is 0.8 ml/min your flow rates are appropriate for nitrogen carrier, which is very slow.

Peter