Dear Yohan,

Do you really need ethanol peak in your chromatogram? If not, then please add solvent delay time in your method (mass spectrometer). This will help you in getting good spectra.

Furthermore, solvent exposure to filament will reduce the filament life. Hence, be careful in running the samples.

if solvent peak is of your interest, (which I do not feel required in your analysis) than just increase the split ratio so that you can get good peak shape.

If I am not wrong, Rtx-624 phase is designed for solvent impurity analysis. This phase selection might be restricting you in quality separation. Therefore, you need to select a suitable column for your analysis.

Hope this answer will help you in solving your problem.

Dr CS Chanotiya, CSIR-CIMAP, INDIA

if ethanol is saturated in the mass spectrum you are damaging the MS. have you tried to set a time to star to run only the MS just after ethanol come out in the chromaogram?

Florentina has rightly pointed out about solvent delay in her answer.

As others have said already, you could be damaging your filament by the huge solvent slug.  If you can, put in a solvent delay even if the solvent elutes between analytes.  You should be able to do this.  You might consider changing your solvent.  I am not familiar with your HS instrument but we run solvent residues by putting the solid samples directly into the HS vial, adding 3mL of water and capping them.  It works great.  If you need a solvent for the sample prep, consider DMF or DMSO which are used for liquid injection.  Modern cross linked columns in GC are not sensitive to water like the older columns were.  Thus, you should not have any issues there.  Not being a lab that runs VOC's, I am not sure if you are constrained by the protocol and if so, then shutting off the filament (solvent delay) would be advisable to protect your filament as others have advised. 

Everyone has given the correct suggestion.  Too much of solvent vapour flowing over a heated filament will reduce it's life.Hence you can set a solvent cut-off time. Once you give a solvent cut-off time, the filament heating will start only after that time period and during this time most of the solvent must have gone.  QP 2010 Ultra is a dual filament system. Are you using HS-20 head space along with your GCMS? 

Solvent delay. I assume EtOH is eluting early. If the solvent is eluting at the middle of your chromatogram you can try to split the scan function into two different avoiding the peak.

Solvent delay. It depends how close the peak is to your compounds. you can always make a program that will turn on and off the detector so you would not see the solvent peak in the chromatogram.

If you are using a programmable injector port, you can set a fix time for evaporation of the ethanol for several minutes before ramming the injector temperature to a higher values to evaporate the rest of the samples. Set the injector temperature and column temperature at the value which only evaporates ethanol first. Then only you start acquisition. Hope this helps. 

Dear Yohan,

I agree with the most opinions that in this case the solvent delay is necessary in use. From one side You must to protect the filament "life" from other side You should to avoid the presence in MS the peaks of the ions of ethanol. If You have the option of turn on and turn off the filament work, please consider it in practice. The changing of the split ratio  of the sample injected is also  strongly recommended. 

I agree with everyone that filament delay and, eventualy, split ratio adjustment will help and are required. My question is: why do you need the ethanol? What is the initial matrix of your sample? The 524 method is a water method and most analytes can be very easily and with good sensitivity analysed using an SPME (on a PDMS fibre) headspace or direct extraction method, which we use in our lab routinelly for disinfection by-products. SPME is a solventless extraction method that works very well in cojunction with GC for slightly polar and non-polar volatile and semi-volatile analytes. The whole extraction/analysis method can be easy automated and works out at about 15 min total time/sample. If you do not have an SPME capable autosampler, SPME can be done manually, by using a syringe-like device.

If You really need some sort of a solvent (check this thoroughly with respect to the already mentioned drawbacks!!!):

for dissolving the samples prior to injection you can use a less volatile solvent with a delayed retention time. Dichlorobenzene for example has a Kovats retention index on a polar column of round about 1500, which means it coelutes with C15. We use DCB on a PerkinElmer Headspace sampler in order to analyze very volatile substances in chewing gum. But take care:

• protect the filament "life" by switching it of at the retention time of DCB
• be aware of the toxicity data of DCB

Add a solvent delay method so that the MS will only activated after the solvent delay time.

Thank you very much for every one, who giving me to valuable guidance on GCMS analysis. 

If the ethanol elutes before the compound of interest, increase the solvent delay time in your method. Good luck.

sir, i have one doubt

why not use DMSO for GC-MS analysis. can you clear explanation sir 

In GC you want preferably to use a protic non water mixable solvents, as the columns are usually quite vulerable to all that.

All akanes do well, all ethers do fine (except THF) chlorinated solvents do fine.

DMSO will probably very quickly ruin your column. additionally it has a very high boiling point and is heavily sorbing to everything meaning you get a lot of DMSO throughout the GC run. - DMSO would be one of the last choices ever I would use on a GC systems ;-)

It is bad enough to us on an HPLC system.

someone please tell me what should be the solvent cutoff time

This is a 3 year  old question....please start a new post.

I fully agree with Chandan add the solvent delay time in your method unless you are interested in solvent chromatogram.

I have the same issue after 20 minutes of total run time ( 60 min) a huge peak is coming and after that no peaks is coming!! Any solution for that is it okay to remove the saturated peak options from setting?? or that will affect my colum & MS

In my opinion You should use GC with the FID detector and the same column as used for GC/MS analysis. In this way You will receive chromatogram of the separated components of Your sample and than You can optimaze the parameters of GC system. The obtained the best separation conditon You may next use for GC/MS analysis. Good luck!

Increase split ratio 1:10 to protect the MS and decrease sample build up