[leUltraNoob1]

Does the retention time for a specific substance depend on the amount injected?

If you inject 0.5 mL of a liquid and measure it's retention time, then inject 0.1 mL of the same liquid, will the retention times be equal or different?

[SiberiaFrogUnit]

On the assumption that you use same GC model, same column, same analytical conditions,
Same substance has same Retention time regardless of the injecting amount.

This is the base of Chromatography.

But it's not absolute so we need open all possibilities.
I read that increase of injecting amount could change Retention time shorthen very slightly on book about chromatography.

So if have suspicion peak, use MSD or spiking sample.

And also inject too much amount, could have some problem like peak tailing, column contamination..

[Stepan]

In GC, retention time generally decreases with increased concentration. This change is in a range of 1% for non-polar compounds and can be as high as 2-5% for polar. 

[SiberiaFrogUnit]

to Stepan, May I ask you that retention time decreasing ratio by increasing concentration in LC??
Like 1% for non-polar, 2-5% for polar in GC.

[Stepan]

Not sure about LC. I think it is not as obvious as for GC.

In GC, the time shift is related to peak tailing. If you observe non-symmetrical peak with a "tail", you should expect RT increase for low concentrations. 

On the packed column the shift if bigger, than on capillary. Retention time starts to increase when concentration of analyte is below 1000 ppm, the most pronounced change is when concentration is below 100-10 ppm   

[SiberiaFrogUnit]

to Stepan, thanks for your answer. I'll remember that.