Chromatography Forum

Hi, I'm new to gas chromatography and ran into this problem: The initial solvent peak is very large (> 14'000 mV) and distorts the chromatogram so that my analytes of interest have small peaks (<100 mV) in relation. To solve this, I wanted to delay the acquisition of the FID to start after the solvent has eluted, however, Chromeleon is reporting this error: "This driver allows acquisition to start only at t=0 min."

So what I did is now to inhibit integration until the solvent peak has passed. But avoiding integration doesn't solve the problem of tiny peaks. While small responses don't necessarily interfere with accurate measurements, the problem is that I have to share this chromatogram with colleges and the peaks of the analytes are not visible next to the solvent peak.

Is there some other way to fix this? It seems the core of the problem is that the instrument driver doesn't support this parameter.

Software: Chromeleon 7.2
GC: Thermo/Finnigan TraceGC Ultra

Thanks for help!

Hello

Just change scale (time and response) in displayed chromatogram so you can see small peaks.

Regards

Tomasz Kubowicz

Hi Tomasz,

Thanks for the idea. That works well, however, the problem is now that the smaller analytes are close to background noise. The concentration of the sample is already high (according to literature) so I can't increase it further.

The largest peak, which corresponds to the component that makes up roughly 60% of the sample is now at only 19mV, and less abundant components are only at around 1mV. This seems out of range for a precise quantification no?

I think because the initial solvent peak is distorting the scale so much, the accuracy of the measurement might actually decrease. Or is this not correct? My reasoning is that the resolution in the range of 4'000-8'000 mV is much higher than in the 1-20mV range.

Hi

Just paste chromatogram and describe method (parameters, analytes, solvents etc)

It will be much easier to help.

Regards

Tomasz Kubowicz

Hi Tomasz,

Thanks for the idea. That works well, however, the problem is now that the smaller analytes are close to background noise. The concentration of the sample is already high (according to literature) so I can't increase it further.

The largest peak, which corresponds to the component that makes up roughly 60% of the sample is now at only 19mV, and less abundant components are only at around 1mV. This seems out of range for a precise quantification no?

I think because the initial solvent peak is distorting the scale so much, the accuracy of the measurement might actually decrease. Or is this not correct? My reasoning is that the resolution in the range of 4'000-8'000 mV is much higher than in the 1-20mV range.

The solvent peak does not distort the scale, you can adjust the vertical scale to make the peaks as tall or as short as you want.

If your peaks of interest are small in relation to noise there is something wrong with your method; as Tomasz says we need to know what you are doing in detail so that we can make sensible suggestions.

Peter