Area counts rising for subsequent injections

[cawarhur]

For the sake of simplicity, let's pretend I have a sample with two components: analyte and solvent. What are common causes for the area count of the analyte to increase between runs when injecting from the same sample vial?

[HbJ]

Analyte carry over somewhere in the chromatographic system.

[dblux_]

For the sake of simplicity, let's pretend I have a sample with two components: analyte and solvent. What are common causes for the area count of the analyte to increase between runs when injecting from the same sample vial?

For the sake of simplicity most obvious reason is evaporation of solvent (from vials - provided it is more volatile than analyte).

[chromatographer1]

Actives sites in the sample flow path which become blocked with the analyte after continued injections.

These active sites could also be sites of catalytic decomposition of the analyes as well. So if they become 'consumed' then more of the analyte peak will elute to the injector.

Of course, all this assumes that your detector is not changing, becoming more sensitive due to some cause.

Murphy is alive and well and has been known to play all sorts of tricks on the unwary.

So be wary.

best wishes,

Rod

[Peter Apps]

If the most simple possible scenario: If you have two runs there is an exactly 50% chance that the peak area for the second run will be bigger than the peak area for the first, and there is absolutley nothing that you can do about it.

Peter

[chromatographer1]

Peter's reply is accurate to within one part per infinity, which is pretty close as far as accuracy goes.

It is possible that the two would exactly match.

But that likelihood is like having two posters exactly agree on an answer, which is also one part per infinity, give or take a part.

best wishes,

Rod

[JI2002]

What's the detector?