Chromatography Forum

what are their drawbacks compared to convention RPLC?

Gee. Do people still have these? I used one (back in the dark ages ), and it worked wonderfully for cleaning up gram quantities of a synthetic peptide. But, the process took 3 days, used lots of solvent, and the instrument itself was large--took up more space than most LC-MS systems. NIH used to keep one on display in the entry hall to building 10--they do look impressive.

these days the instruments are a lot smaller and a lot more efficient
these are mainly prep systems for purification
the 2 main important draw backs are:
generally less separation power than for column chromatography
you are doing partition chromatography basically with imiscible solvents lot less knowledge and support out there for that.

the main advantages if you have an application for it:
no cost of column, and silica, in big prep no more need of packing the column. this is a huge saving cost in money and time
you can do a reverse in flow direction and save time in the chromatography
these systems are easier to set up so as to work in continues mode and not only batch mode
they are greener instruments, most of the solvent can be recycled and it is easier to use on-line solvent recycling.

CCC can do some things very well. They have very high capacity and no loss of compound. OTOH, they have lower resolution than other forms of chromatography. I don't think there's a systematic method development as there is for other chromatography (I may be wrong here & would be happy to learn otherwise).

Ther is a similar technolgie to CCC called CPC, the difference is that CPC has chambers instead of coils.

I think the main drawbacks are:
-its only a preparative technologie
-everybody knows HPLC, so it seems easyer to go for prep HPLC
-some applications run better with HPLC ( Isomer- or enatioseparations)

the benfits are:
-some application run better with CPC or CCC (natural compounds)
-no solid phase (you can pack the "column" just pumping the liquid stationary phase into the system)
-no precleaning of the sample
-less solvent consumption
-no irreverisible adsorbiton on SP / loss of sample
-the prediction of selectivity and loadabillity is very easy compared to HPLC

Best regards
Chris

what is the underlying principle of their low resolution?
since they do not have particles, they do not have A term or less A term. so it should have high plate count.

CCC can do some things very weell. They have very high capacity and no loss of compound. OTOH, they have lower resolution than other forms of chromatography. I don't think there's a systematic method development as there is for other chromatography (I may be wrong here & would be happy to learn otherwise).

since they do not have particles, they do not have A term or less A term. so it should have high plate count.

The Knox / van Deemter equations do not apply to countercurrent systems. Each loop of the coil or each chamber is 1 plate.

Hi Tom, could you explain to me in principle (hydrodynamic aspect) why countercurrent chromotography is not popular? Thanks so much!

since they do not have particles, they do not have A term or less A term. so it should have high plate count.

The Knox / van Deemter equations do not apply to countercurrent systems. Each loop of the coil or each chamber is 1 plate.

The popularity (or lack thereof) has little to do with the hydrodynamic aspect, as indicated by many of the other posts. In fact, in the classic "Craig" apparatus, hydrodynamics are completely irrelevant. Each transfer equals one plate. In fact, that's the origin of the term "plate", borrowed from distillation as a shorthand way of saying "a discrete stage of equilibration between the phases").

so the problem of counter-current chromatography actually is the lack of plate numbers?

The popularity (or lack thereof) has little to do with the hydrodynamic aspect, as indicated by many of the other posts. In fact, in the classic "Craig" apparatus, hydrodynamics are completely irrelevant. Each transfer equals one plate. In fact, that's the origin of the term "plate", borrowed from distillation as a shorthand way of saying "a discrete stage of equilibration between the phases").

You are trying to attribute to me a statement which I have not made . I don't think you can reduce "popularity" to the effects of a single parameter.

The pros and cons of CCC have been well presented by unmgvar, Jack Silver, and Chris0000. The concept dates back to the 1940s, and I'm pretty sure that the "Craig" apparatus was around when I started doing chromatography in 1968. Over the years, it has been eclipsed in popularity by (in turn) column chromatography, thin-layer chromatography, and HPLC. It's a complex and expensive technique to implement and while it does a few things well, those are not general enough to make it competitive.

sorry.
Really thank you for your comments! I learned a lot from you.

You are trying to attribute to me a statement which I have not made . I don't think you can reduce "popularity" to the effects of a single parameter.

The pros and cons of CCC have been well presented by unmgvar, Jack Silver, and Chris0000. The concept dates back to the 1940s, and I'm pretty sure that the "Craig" apparatus was around when I started doing chromatography in 1968. Over the years, it has been eclipsed in popularity by (in turn) column chromatography, thin-layer chromatography, and HPLC. It's a complex and expensive technique to implement and while it does a few things well, those are not general enough to make it competitive.

No problem! I was just trying to clarify.