radial temperature gradient in LC

[MaxSpecs]

Hi,

Would radial temperature gradient cause fronting or tailing, and would it depend on the direction of such gradient?
I'm seeing conflicting reports on that.

(scenarios: the column core hotter than the rest, e.g. in frictional heating and the column core colder than the rest, e.g. inefficient through-the-wall heating).

Any thoughts on that?

Cheers

[Multidimensional]

Internal column heating (as seen in some UHPLC applications run at very high back pressures OR in some Prep Systems with high flow rates) can result in all kinds of abnormal peak shape and poor reproducibility problems. To troubleshoot the issue, start by first checking the fundamentals to make sure your method and technique are sound, then try reducing the sample load by 10x (or more) and/or reduce the flow rate.

However, most peak shape problems are fare more likely to be due to other very fundamental errors in chromatography method development such as sample injection overloading, use of an injection solvent which is too strong, not fully dissolving the sample in the injection solution before injecting, use of the wrong injection solution, poor quality method...

BTW: I mentioned this topic to my boss and he commented that the upcoming January 6th, 2018, "HPLC HINT's and TIPS" blog post will be related to your question. The soon to be available article is about "Column Frictional Heating Effects Causing Poor Resolution and Peak Shape (and how to correct for it)". The post, when available, will be seen at this link: https://hplctips.blogspot.com/2018/01/uhplc-tip-reducing-column-temperature.html

[mattmullaney]

Hi MaxSpecs,

This link:

http://www.chromatographyonline.com/ult ... l-issues-0

provides some items to consider on page two, and provides some additional references (4, 5, 8, 9, 10 and 11). The condensed version: radial thermal gradients are more of a problem with increasing column width and different column heaters have different ability to dissipate radial thermal gradient effects.

Longitudinal thermal gradient formation seems to be an issue at high running pressures (> 1000 bar), with increasing column length and with smaller particle size (< 2 microns).