Chromatography Forum

So, it calls for a lower temperature and not higher. Or was the goal broader peaks?

With regards to pressur, unless one has installed a restrictor (typically on the detector outlet) on purpose, in order to generate some pressure on the flow-cell, which often is a very good idea, the presser will be zero, if there’s no column installed. Anyway, when conventional mobile phases are utilized. So, I don’t think we need to worry too much about the system’s intrinsic pressure.

Best Regards

JUst to repeat what was siad about the DRI detector. The refractive Index is temperature dependant. So if the temperature changes the DRI changes so you have to control the temperature. If you only have a heater then the only way to control the temperature is by continually providing heat but varying the amount of heat going in according to the heat being lost. ie if the outside temperature heats up then you hesat less. To have an effective control you need at leats a 10 C difference between the ambient temperature and the controlled temperature but most people like nice round numbers so lab temp 25C gets heated to 35C which gets rounded up to 40C.

The real answer is buy a DRI with a Peltier Heater and Cooler as this will allow you to operate at any temperature you like, which can be very important with biological materials.

The chap who figured out the diffusion Laws was named Fick, never heard of a Fisk.

As I said before, I can imagine that there are some solutions which may have a significant RI temp. dependence, but I can´t imagine that anybody has conditions which would require an active temp. control of the CELL.

The chap who figured out the diffusion Laws was named Fick, never heard of a Fisk.

As I said before, I can imagine that there are some solutions which may have a significant RI temp. dependence, but I can´t imagine that anybody has conditions which would require an active temp. control of the CELL.

I use an RI with light scattering. In this case, the absolute value of dn/dc is quite important. And, there are very few examples where the value of dn/dc varies enough with temperature to cause problems. Here, "very few" means I don't know of any, but recognize it is a big world.

That said, I haven't seen an RI for batch mode or GPC use that does not have temperature control. To split hairs, the oven surrounding the cell is kept at constant temperature and that eliminates gradients. But, this is the sort of esoteric distinction that usually confuses more than it enlightens (unless you are designing the thing). I don't know of any better way to keep the cell temperature uniform.

Here's a more practical way of looking at things. If you don't have much drift in your RI, the temperature control is "good." If you have a temperature control problem, you will see a lot of drift. Unfortunately, there are lots of reasons for drift. Temperature control is usually at the bottom of the list.