Hi everybody,

I am analysing VOCs emanating from plants by GC-MS. Since I moved lab I am trying to get the analyses running on the GC-MS of the new lab. However, I have difficulties getting good peaks of green leaf volatiles (e.g. hexenal, hexenol) and other short chain compounds (e.g. n-octane, which I use as Internal Standard). In contrast, the other larger compounds (mono- and sesquiterpenes) are doing fine.

In the old lab (where everything was fine) we basically had the same GC-MS system, the same column and the same method. The only difference I see is that we have no retention gap here. Also, we have two columns installed (one for split/splitless, one for on-column) which are connected before they go into the MS. So, what could it be? I would be thankful for any suggestions.

Here are further details of the method:

GC-MS from Agilent/ 6890N/5973N
Column: HPms-1, 0.25 mm x 30 m x 0.25 µm
Solvent: methylene chloride

INLET
Inj vol: 2 µl
Pulsed splitless inj
Heater: 220°C
Pressure: 11.6 psi (80 kPa)
Inj pulse pressure: 11.6 psi until 0.65 min
Purge flow to split vent 200 ml/min@0.65

Constant flow of He 1.5 ml/min

TEMPERATURE PROGRAMM
40°C for 3 min
increase by 8°C/min to 230°C