Chromatography Forum

Hi,

Where can I get information on fast hplc?

thanks for ur time

If you contact me, I sent you a few papers.

here is a very commercial but interesting source:

http://www.eksigent.com/expresslc.htm

You might also try Waters website for the new Acquity LC system. We have one and the user is very pleased with the results and system performance so far.

Regards,
Mark

Be careful about the Acquity system from Waters. The same time savings can be had with most exising systems, simply by using 3um column packings. Waters will lock you into their proprietary columns. special hardened fittings are required for tube fittings (available only from Waters, of course) and they still can't beat physical laws-if you get speed, you give up resolution (remember the old triangle). Many of these posters are Waters personnel!

Be careful about the Acquity system from Waters. The same time savings can be had with most exising systems, simply by using 3um column packings. Waters will lock you into their proprietary columns. special hardened fittings are required for tube fittings (available only from Waters, of course) and they still can't beat physical laws-if you get speed, you give up resolution (remember the old triangle). Many of these posters are Waters personnel!

OK - please refrain from vendor bashing. Those of us who frequent this board are aware of who the vendor employees are. Aside from the one conference seminar thing, the bashing is not warranted.

PS - Waters' Acquity system does not require their proprietary columns. Regular columns can be used on the systems (just don't over pressure them). Give it a week or two and you will almost certainly be able to buy appropriate fittings from a number of vendors besides Waters. Physical laws are behind the Acquity system - the higher sustainable pressures means that they can go with smaller particles in the columns, which means more plates. When you use a lot more plates (Res. is proportional to N^1/2), you get better resolution.

PSS - I do not work for Waters, and I do not run an Acquity (but if Uwe wants to send one my way, I'd be happy to try it out!).



bashers---><-----Mods

I certainly didn't intend to "bash" Waters-I just wanted to offer some pointed criticism, which I feel they deserve. You can certainly use conventional columns with the Acquity system, but then it would function as a conventional system, so what's the point? From what I've seen, they've (as usual) taken existing technology and very cleverly packaged it as something completely new and different. My comment about the laws of physics was to indicate that contrary to Waters marketing materials, you cannot increase all three parameters-speed, resolution, and sensitivity-at the same time. Optimizing the value of one of these parameters always results in a loss in one or both of the others. Finally, I'm glad you know all the Waters people who post here-I'm new to this forum, and I certainly don't-do they generally clearly identify themselves?

Elmiko,

I am from Waters, and most people know that. I have also written the textbook on "HPLC Columns", as well as many pieces of literature or articles in other textbooks.

Here is what the real story is, and there is no way to deny this. As one goes to a smaller particle size, both the speed of chromatography and the performance per unit time increase. This happens at the expense of backpressure. Once you get to a particle size below around 2.5 micron, and you still want a column length that gives you a high performance, you need higher backpressure. This is not marketing, this is a fact of life.

Sensitivity has little to do with any of this. Sensitivity on its own is a complicated subject which depends on column dimensions as well as performance, and of course also on the detector.

If you do not believe what I have written, you can check up on publications by Jorgenson, the inventor of capillary CE and a respected scientist. He is the one who did the first work on ultra-high pressure separations. You may call him the father of ultra-high pressure LC. Waters is only implementing his ideas to make them available to the general public of chromatographers.

Uwe,

As an add on to this discussion, considering that the benefits for ultra high pressure LC have been known for a while, why has it taken so long for instrument / column manufacturers to develop the technology. Has it been the difficulties in developing the pumping system or creating stable small (sub 3µ) particles?

Rob

Rob,

When I was young, I believed that the progress of science and technology is marching on a fairly straight path. Over time, I have learned that the path is often fairly convoluted. The bottom line is best described with a German proverb: "Gut Ding will Weile haben", with the rough translation: "A good thing takes its time"...

Huge backpressures are not necessarily a consequence of using smaller particles and performing faster analyses. You can get the same advantages of using ultra high pressure by increasing the temperature. I can provide information if anyone is interested.

I am interested.

It is correct that one can speed up an analysis by increasing the temperature. See my article in the J. Sep. Sci. 24 (2001), 921-929. The potential disadvantage of this approach is the question of analyte stability.

I have seen very little evidence of thermal degradation, and I work at temps up to 200 C. There are more advantages to increased temp than just faster runs.

For those interested in high temp HPLC, you can get more info at our website, www.selerity.com, or email me.

Regarding analyte stability, I would look at tech notes 801 and 807 (under the literature section at the Selerity website). We also have a few published articles on the subject. I will dig up the references and provide them if anyone wants them.

Reaching a high but stable pressure is a not an easy job. The hardware (pumps, tubing fittings, columns, etc) has to be made in a way to endure the ultra-high pressure. It will definitely increase the capital cost of the whole system as well as the maintenance.