Purpose of cooled LC autosamplers?

Discussions about HPLC, CE, TLC, SFC, and other "liquid phase" separation techniques.

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Hi everyone,

I'm looking at autosamplers for my HPLC system and I've come across a few that are have a built-in cooling/heating system (eg. Shimadzu SIL-20A). My question is why would I need to this. Is this to prevent highly volatile liquid samples from evaporating and escaping the 1.5ml vials? Or something else.

I completely understand the need to have heated autosamplers for GC for headspace applications (eg. HS-GC, SPME-GC, etc) but for LC, I'm not sure what the purpose would be?

Any input would be great, sorry for the dumb question.
As you said, preventing sample evaporation (concentration change, crashing out).
Also preserving the analyte if unstable, especially biologicals ( often 4c required) - watch out if lab temp not too high for that (cooling efficiency).
Having the option to cool or warm the samples is very useful for some applications.

One common use of an A/S with a cooling feature is to provide stability to thermally labile compounds. You do not want your sample decomposing or degrading while it is sitting in solution waiting for analysis. Cooled A/S provide a simple way to maintain and control the sample temperature before analysis. Almost all of the major HPLC instrument vendors offer cooled/heated samplers.

BTW: Heated samplers are used for a similar purpose. Again, to maintain/control the sample temperature. For example, many users who work with cell, bacterial or clinical samples maintain samples in the A/S at ~ 37C for analysis.
Thanks MaxSpecs and Multidimensional for your input.

I figured it had something to do with stability and of course it makes perfect sense for biological samples. I'm coming from the GC world where the majority of the A/S are heated so getting my head around a cooled A/S was a bit foreign to me.

Thank you again for the input!! Very helpful.
As others have pointed out, the option is primarily for stability, especially in ADME/DMPK analyses.

Also to clarify - the Shimadzu SIL-20A is heated only. The SIL-20AC has heating and cooling.
… just a remark, in some environments it becomes a habit to keep all samples cool, in hopes of improving stability. Then one day analytical people decide to do semi-prep chromatography (many modern pumps can do 5mL/min nowadays), and suddenly they're using a sample that they've only just got into solution with gentle warming. They put it in the cooled autosampler and it crashes out of solution, and blocks the tubing between the autosampler and the column oven (and you don't want to think about how much that tube costs...).
LC Autosampler manufacturers really do take stability seriously. The Waters sample managers with windows, for example, have UV-opaque plastic in the window to avoid light degradation even if you don't use brown vials (and that's also why you can turn the light off in the autosampler!).
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