Chromatography Forum

My system has about 10% peak area change for 10% flow rate change.
ie. 0.9ml/min peak area is about 10% higher than 1.0mL/min, and 1.0 mL/min gives about 10% higher area compared to 1.1 mL/min. How is this possible. No interfering peaks near the major peak, retention time changes as expected. No tailing or integration errors. Injecting 100uL which is the maximum possible.

You can figure out yourself "how this is possible": What do you think will happen to the area if you stop flow while the peak goes through the detector?

Hi Ranjith,
It is quite satisfying when theory and practice are in agreement with one another! What you’re experiencing is what one should expect.
You see the slower is the flow-rate the longer it takes for the analyte to pass through the flow-cell and thus the broader is the peak. The peak height on the other hand is roughly the same (within reasonable limits – see also some van Deemter discussions for more clarification on this particular matter) so when you multiply the peak height (roughly constant) by the peak width (which is inversely proportional to the flow-rait) you observe these differences.
The above is one of the reasons for chromatography to be regarded as a relative measuring technique – i.e. one needs to employ standards (known quantities).

Best Regards