the capacity factor

[MestizoJoe]

i recently calibrated an HPLC instrument. in order to pass the temperature precision test i needed a capacity factor between 0.9 and 1.8. the run i carried out were all the same except the temperature of the column was altered. how does this experiment prove that the temperature is precise? is that even what it's trying to prove?

[JA]

I find it interesting that you can show the precision of a column heater by monitoring the variation in retention time for some chemical probe.

I wonder what upper and lower limits of temperature give you k' values from 0.9 to 1.8 in your method, all else being equal. If I recall correctly a rule of thumb is approximately 1% change in RT for a 1°C change in temperature, so this looks like quite a wide working range.

I would expect that temperature accuracy and precision would be better demonstrated using a certified thermocouple. With all the other variables in any particular HPLC methodology I don't see how retention time variation can be attributed to temperature alone.

[unmgvar]

you experiment is interesting.

for it to be anything close to valid, does it show the translation of the K' value to temperature values?

[HW Mueller]

Maybe it is just a misnomer for a test of temp. on retention time?

[aceto_81]

This looks like the test for temperature accuracy from Waters.
I think waters allows 5°C deviation from the set temperature, so this is also a large range.

One can verify the trueness of the test by setting the temperatures, verify by an external temperature probe and inject. Do this for 30°C, 35°C, 40°C, 45°C and 50°C and you know wether the test is correct or not.
(And please let us know)

All the best

Ace

[rhaefe]

This is simply a van't Hoff plot (lnk vs 1/T). In most cases pure reversed phase separations will give a linear relationship, so one can indeed calculate temperature from retention factors.
This relationship can become very significant if the samples undergoes a structural change at a certain temperature. Denaturing HPLC (dHPLC) is such a case where separation temperature control down to 0.1 or 0.2°C becomes necessary.