Hi Roxanne,

What is the column temperature ramp? 

Dusan

Hi Roxanne

Without further method details I can already think of two possible causes: the wrong type of column and/or overloading. What type injection do you use, i.e. split, splitless, on column..? My suggestions:

good luck :)

Hi Roxanne,

what is your objective, you want to know the purity of those solvent ? if yes, decrease the injection volume and go with split starting with low oven temperatures. Try with 624 column will give good seperation

Hi all,

Thanks already for the suggestions!

I'm trying to detect the chemical compounds of the body odour of a pangolin, with solvent extraction out of swabs. And because I don't know what I'm looking for, I'm using this general column Rtx-1. For the solvents I'm looking for the fact where those solvent come off to put on my delay time.

Splitless injection method

Injection temperature: 300°C

Injection volume 1µL

Flow rate (He): 20.00 psi

Oven temperature programme:

* 80°C for 3 minutes

* Rate 20°C/min

* Until 300°C held for 15min

FID detector Temp: 280°C

Hi Roxanne,

The temperature ramp seams right. I suppose you have 60m column. From what you described I thing that you have high amount on solvents loaded onto your column. I usually use methanol and ethanol (as solvent for internal standard) and they not escape in first 3 min under similar temp ramp. The simplest thing to try is to use split 1:100 and see how it goes, but this will dilute your sample as well, so you may want to try to decrease the dilution factor.

Nice project, by the way.

Hi Dusan,

I only have a 30m column. Would that be something to think about as well?

Thanks for the advice as well, I'll try different things today to see what works.

The solvent peak width in splitless injection is affected by your splitless time, i.e., the time before you open the split valve.  What splitless time are you using, and have you optimized it?

This is how the pure methanol solvent looks like after analysing it with that method.

Roxanne, I would suggest not to try solvent extraction of swab for volatile organic compounds (VOCs) of body odour. Alternatively, place swab in a 2-4 mL vial with septum and do solid-phase microextraction (SPME); you may heat the vial possibly to 30-50 deg C on a hot plate while extraction. On placing in the heated injector, VOCs are eluted from SPME fibre and introduced into the GC column. There are plenty of papers available. So, you get rid of solvent peaks and early eluting VOCs are also seen. Best, perform GC-MS for characterization. Good luck.

Contd. Your methanol chromatogram is very typical, a common experience on capillary columns even after splitting. 1µL of neat solvent is a lot of material (on mass basis) loaded.

Hi Roxanne, 

For such biological samples longer (60m) column could be better, but it is really up to what you have and how much you want/can invest in this.

I agree that SPME would be better for the nature of your experiment, and GC-MS instead of GC-FID. Whit only FID you will have real challenge to get any compound identification. Following this, ideal would be to do your experiment on entirely different (more sensitive) instruments (PTR-MS or SIFT-MS). If you have access to PTR-TOF-MS that would be perfect ( just put your sample in 1L Teflon/Tedlar bag, fill with zero air/nitorgen, incubate it 30 min on 30-40C and run).

Good luck. 

Hi Roxanne,

I just noticed that you are not far form us. Please check if your university has a research agreement  with us. If so please contact me on [email protected] as we do very similar projects an you might want to initiate short collaboration or at least visit us in order to get idea what and how the team here is doing the similar stuff. My supervisor is involve in this and I am in position to organize a lab tour.