Filling empty space in a column heater

[Cardinal Fang]

We run an old Waters HPLC system for amino acids, which has an old TCM column heater unit. I've finally got round to tidying up the system, including removing all of the columns for old dead methods from the column heater (yes I know, they should have been removed when the method was retired. But that pre-dates me on the section).

As we only run 1 method on this system now (amino acids using the Waters Pico-Tag method), there's now only 1 column in the unit.

As the TCM heaters don't have fans or anything, I'm assuming that this means that temperature distribution might be poorer and inconsistent compared more modern column ovens, so that there are cooler spots and warmer spots along the column.

Anyone have any ideas for improving temperature consistency and efficiency? (Please don't say "get a better/ newer system". Budgets mean that's not an option)

I was wondering whether filling the "dead" space with something like metal ball bearings might work.

[Consumer Products Guy]

I'd cut some flexible foam sheets and press in there before I'd try anything metal.

Edit: on second thought, maybe just buy a more-modern column heater, even used.

[Hollow]

Actually I don't know the TCM in real but from the pictures on the web it's just a heated box.
So I guess you could just fill the excessive void with aluminum foil, also put some of the foil on top of the column.
Don't know how the tubings are laid out, maybe you want to put some extra length of SS tubing in the box before entering the column to preheat the eluent.
If you don't like to fill everything with foil, maybe you can cut a solid block of aluminum or cooper to fit in the TCM and cut a notch for the column.
If I remember, this is what J. Dolan presented in his classrooms.

If the thermostat is working well, I guess a well filled box with few free space and with a tubing for preheating the eluent will not be inferior to "modern" models (if I look at the (first) Acquity UPLC CM)
Also I would prefer metal over foam because of it's heat capacity.

[uzman]

Column heaters ; including TCM ; are designed to control the temperature within required limits and several parameters are taken into consideration ;such as volume , heat loss ,heating rate ,heating power etc .

If you change a parameter , such as volume , then the stabilisation time and also the accuracy may change.

My opinion is ,use it as is.

[mattmullaney]

Hi Cardinal Fang,

Along Uzman's line of thinking, have you tried out the system as it is to see if the PicoTag separation works as it normally used to beforehand? "If it isn't broken, there may be no reason to fix it."

[Multidimensional]

Please do not worry about it. Save your foam blocks and aluminum foil which will not help you much. Instead, think about the job that a column heater really needs to do and why we use them. Running without a column heater/cooler introduces variability in results because temperature is a key method development variable. We want a stable temperature. Once a temp is selected, it must be maintained to within +/- 1C. This is fundamental to HPLC Method Development.

Any good HPLC system must have temp control of the column. Most every column heater/cooler on the market does not actually keep your column at the specified temperature seen in the software or display. The temp shown is not for your column, but the heating element in the chamber. You have what we refer to as a "block" style heater. The aluminum fins provide the surface area which is heated. The column end fittings come in contact with the fins (usually aluminum) and any heat transfer which occurs moves into the steel column. The column will be different temperatures inside and probably not what the set temp is at all (because the temp sensor is on the fin, not the column). Because columns have liquid running through them, a temp grad exists inside so the temp is not even uniform, esp using a block heater. The "temp" shown is arbitrary.

So why do I say, "do not worry about it"? Because since all column heaters end up bringing each column to a different actual temperature (and a gradient of temp too), you can not expect one column heater from one company to ever match another from a different company. The reason it does not matter is because we really only need temperature reproducibility, run-to-run. That is the most important variable we try to control with column heaters. If the column temp changed for the runs across a day, then so would the Rt (and the results too). So we use these column heaters to establish a consistent temp all day which helps us control this variable and improve our chances of getting good % RSD each time we use the method. IOW: You only need stability. Keep the oven closed up tightly and the column pressed firmly against the metal fins or cavity in the chamber. Plug any holes to the outside.

[Cardinal Fang]

Cheers for all the responses

[mattmullaney]

Hi CF,

Best Wishes going forward with the work!