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Bischoff- POPLC

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

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Does anybody have any experience with POPLC?
Is it worth buying?
It seems quite usefull, but i do not know anyone who uses it.

I never used it myself. The philosophy behind is looks good.

What I heard from the field is that for isocratic separations it works nice, in gradient elution it's not very effective.

I will test it myself too.

When you say it is not effective for gradients, do you mean the columns or the software?
Mark Tracy
Senior Chemist
Dionex Corp.

There are several things that complicate the story.

1. In isocratic separations, the retention times add up, but not the plate counts. A mixed column system always has a plate count that is much lower than the plate count in a system with the same columns. Proven by Snyder and Sternberg long before I knew what chromatography is, and this is a long, long time ago...

2. Even simple things like retention times do not add up in gradients. In simple terms, you get in gradients more or less the separation that you would get from the column segment with the longest retentivity. So why bother putting the other columns in... (reality is a bit more complicated than that, but this is a good first cut).

we have not used it but we also looked at the system.

basicaly what everybody is looking for is the best possible resolution for the least amount of time.

resolution is a result of combination between efficiency (N); selectivity; capacity

most important vendor solutions have been to go and boost the plate count number of columns= smaller particle size. but that only contributes in the square root.

the POPLC is a different appraoch. this goes to the stationnary phase selectivity. they are not looking out at the N too much. they developed a software that works on the prisma principle between 5 different stationnary phases.

is it a bad aproach? well in theory no because absorption chromatography is first of all choosing your column before you look at something else. i think that most of us have gone lazy looking for solutions provided only by c-8 c-18 columns.
it seems like a good possibiliyty in my view.

one con is that you can only work isocraticaly with your solvents. for long run your bound to have peak broadning effect.
the main con if you are in a regulated environment is to be well prepared to explain that system to your bosses who will think only of the questions that might arose if you get inspected. that is where we got stuck :wink:

ask them to do a real demo with some of your stuff. it should not take more then a day's work to get a first impression.

unmgvar wrote:

the main con if you are in a regulated environment is to be well prepared to explain that system to your bosses who will think only of the questions that might arose if you get inspected. that is where we got stuck


Unfortunately this is the present-day truth. It confirms once again that the chromatographic market is very conservative. This mentality also slows down/complicates all new LC developments.

Uwe Neue wrote:
.
1. In isocratic separations, the retention times add up, but not the plate counts. A mixed column system always has a plate count that is much lower than the plate count in a system with the same columns. Proven by Snyder and Sternberg long before I knew what chromatography is, and this is a long, long time ago...


No doubt about this, but in most isocratic separation the selectivity dominates over the plate number. Unless you don’t loose a factor 10 in plates, I don’t see this as a limitation.

Nevertheless I have my doubts about the practical feasibility of this approach. The suggestion to ask for a demonstration sounds like a good idea.

Do a bit of back-of-the-envelope calculations about what happens when you put mixed columns together, and you will learn very quickly that most of the time, you will loose more than what you gain in this game of putting different column chemistries in series.

Mark Tracy wrote:
When you say it is not effective for gradients, do you mean the columns or the software?



In general, we apply POPLC for gradient separations. We use it in combination with ChromSword Auto. At first, we perform "screening gradients" on each of the 5 POP linked columns (length: 6 cm each) by means of a column switching module. Subsequently, we combine a POP linked column and repeat the screening gradients. If the chromatograms promising a good separation, we perform an automated "fine optimization" to get the final separation. We do not use the POP linked Optimizer for the gradients. POPLC is a very good tool for optimizing problematic separations. :lol:

Pfeffer_BSP wrote:
In general, we apply POPLC for gradient separations. We use it in combination with ChromSword Auto. At first, we perform "screening gradients" on each of the 5 POP linked columns (length: 6 cm each) by means of a column switching module. Subsequently, we combine a POP linked column and repeat the screening gradients. If the chromatograms promising a good separation, we perform an automated "fine optimization" to get the final separation. We do not use the POP linked Optimizer for the gradients. POPLC is a very good tool for optimizing problematic separations. :lol:


Hey, if it's working for you that's great!. Provided it doesn't break any condientiality issues, I was wondering if you would be kind enough to provide an example of the process, just to help me understand where the benefits appear.

The aspects of interest to me are:-
How complex is a typical sample?
How do you decide which peaks have critical resolution requirements?
What are the five column phases?
What are the screening gradients?
How quickly does the selection process identify what should be used for the automated fine optimsiation. In other words, is the gradient varied or the column selection varied?.
How long does the process take for a typical sample?

Thanks very much, and please keep having fun,

Bruce Hamilton

Ok, this is fine...

But what happens in a gradient if you switch the the position of the POP columns???

Or - more interestingly - what happens to your gradient separation if you just plainly take out the column with the weaker retention?

I'm curious: what does the POP of POPLC stand for?.... maybe I'll have a look on Google... cheers..

Rob Burgess wrote:
I'm curious: what does the POP of POPLC stand for?.... maybe I'll have a look on Google... cheers..


POP stand for: Phase OPtimized

thanks
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