Take into account that your choice of solvent also needs to fit with the column type. Some columns cannot handle ethanol or acetone, you would just wash away a little bit of the stationary phase with each injection if you happen to have such a column.

Are you using a split or splitless injector. In case you use split injector, what is the split flow? Or do you have a PTV injector?

Hi Harinder

You can have different effects.

It can be a regular by-effect of solvent/column/program...try another solvent (more unpolar/polar) maybe the effect is reduced.

What column and what injector/liner do you use? How many samples do you run per day and how is your service intervall.

The membrane or the liner sealings might leak, the split mechanic can be poluted or impropper in function, the split-inline-filters might be closed or if you use a workstation: the D/A transformer might have difficulties with the split/splitless switching.

It is usual to get a big solvent peak at the beginning of elution..however if it is going to very huge then some leakage should be there in the system.. As Frank hoger stated the different possibilities may also cause huge solvent peak..Your GC may be serviced to rectify the problem..I dont feel there is any technical issues.

Good afternoon. I agree with the above ansewers. Despite I'm not a specialist in GC, my experience tells me that you may also try another split ratio, increaseng the flow that goes to waste (in the case that you are using a split injector), or simply concetrate your sample, if possible (i.e.,if concentration doesn't damage your sample).

Hello,

Could you check if you have still the issue when injecting 1µl ?

It simply can be a backflash (solvent expands when

vaporized to a volume that is larger than your liner volume)

There is a nice tool to calculate it (in the link i send you)

Nevertheless you should consider to :

1/ Check your injection mode in your instrument method (split is good)

2/ Make a leak test (if it fail change septum first)

3/ Inject something well know on your GC to verify if there is nothing wrong with your equipement (SST)

4/ Maybe change the liner

http://www.chromacademy.com/essential-guide/Aug_2012/fig-22.swf

Thanks for the suggestions. Engineer visited few days back and serviced it, so there is no technical issue (leakage/septum). I read that apart from technical issues, three things can solve the problem: increase Injection temperature, decrease injection pressure, and increase split ratio. I tried injection temperature and different split ratios . Solvent peak did come down, but did not vanish. Recently, I asked the column customer support guys and they told me that in GC-FID, solvent peak cant be avoided. I can change my solvent, but I can not do that. Anyway, my sample peaks are quite away, so it is not bothering me. But I am curious to know:

1. Changing injection volume from 2 to 1 ul can solve this?

2. Is it a fact or varies from lab to lab, that solvent peak comes in the beginning? I am talking about GC-FID and not GC-MS, where delay option is there.

Sometimes changing the liner can fix this problem too.

Some liners have a kind of wool to facilitate evaporation but this can also gather dirt or not very well volatile solvents/molecules (that condensate in, depending the injector temperature).

For each analyse, add a blank (dilution solvent alone) and a SST in your sample table before your samples to check if everything is alright (especially if you are not alone to use the GC)

And yes you will always have a solvent peak at the beginning of your chromatogram.

I think that is you have a huge tailing solvent peak that gets in the way of your analysis all the above suggestions are valid.

However, you will always have a solvent peak in GC-FID. THe matter is that you have to choose a proper solvent with low boiling temperature so you can get it off the column in the void volume and not bother your analysis.

Obviously the solvent peak will be the largest peak, since your solvent will always be the most abundant molecule in the 0.5-2 ul that you inject on the column.

In GC-MS you can avoid the solvent peak, but commonly just by not recording the first 2-3 minutes, in which the solvent peak gets eluted.

It depends upon detector used. Preferential solvation of analyte in one solvent in case of binary or ternary mixture of solvent is one of the reason, that slightly leaves different composition of the mobile phase and solvent elute at the dead volume of the column and that can have different different RI for example and it would have a peak at dead volume. On the other hand, it wont be present in signal of UV detector or ELS detector etc.

One of the factor is no doubt the injector (as pointed by certain readers). However, I would like to add that, if you can change the solvent to some other material like ethanol or acetone, I feel that this problem can be overcome. Secondly, I suggest that you slightly concentrate your sample so that instead of 2 micro liter you can cut it down to may 1 micro liter or less and the solvent peak would reduce too.

Take into account that your choice of solvent also needs to fit with the column type. Some columns cannot handle ethanol or acetone, you would just wash away a little bit of the stationary phase with each injection if you happen to have such a column.

That is because of the high temperature. If you want to know what is happening, just run without injecting anything. You will get the same result. This is not the solvent peak, this is the sensitivity of the system that cause it. You must find a way to equalize it ie; use a double column system with two detectors.

may be any solvent that you inject in the system will get the same shape  the temperature may be is too high and in case of solvents I prefer use injection by head space mode.

also you must use solutions with less concentration and a bigger Split ratio 1/200

best regards

If you are using capillary column GC, increasing the split ratio will help. Also, begin collecting data after the solvent peak elutes. You may have to begin at a lower initial temperature and hold until the solvent elutes, then begin data collection. I could provide more detail if I knew what the target compounds were and the concentration. 

This is a common problem while making large volume injections (LVI). LVI is required for many residue analysis like pesticide residues in foods etc. Since the target is dissolved in a suitable solvent, naturally the solvent portion will be higher when making LVIs. Many times, the target peaks get merged with the solvent peak and hence you will not be able to detect it. The solution for this is to use PTV (Programmable Temperature Vapouriser). PTV is a type of injector where you can programme the temerature. At the time of injection, PTV is kept at a low temperature and the Split Ratio is kept very high. This time most of the solvent escapes through the split vent. After a certain time period, the Split Ratio is reduced to a very low value and the PTV temperature is suddenly raised to a high value. The targets now vaporise and go to the column. Thus you eliminate the huge solvent peak and increase the sensitivity of detection for your targets.

I agree with Girijan. However, if you do not have a PTV, and if your sensitivity requirements do not allow you to use a split ratio, try using a lower start temperature for the column, in fact I would go as low as possible (35 C is possible in my lab without cooling the oven). Changing the solvent is not a posibility? If you give us more information about what you are trying to separate, you may get more appropriate suggestions.

Increasing the split ratio can be helpful

very dilute samples or high attenuation