Dwell volume Agilent 1100

[bunnahabhain]

Hi everybody

I am trying to reduce the dwell volume of my Agilent 1100 as far as possible. I basically exchanged all capillaries with as short as possible red PEEK (described in this document). The only capilaaries remaining are the ones from and to the pressure damper. Does anybody know what ID these have? Will it be worth replacing them with 0.13 mm ID steel capillaries?

Thanks a lot
Jörg

PS.: I am going to use this system at flow rates below 1 mL/min exclusively. How small can I choose the ID for tubing from the quaternary gradient valve to the pump head? Will 0.25 be OK?

[carlo.annaratone]

Hi,

I just went through a very similar process in order to bring down the dead volume of my agilent 1100, in order to use smaller columns and flows. I kept the original tubing from the mixer to the pump, and replaced every other tubing (including those between the pump head and the pressure dampener) with precut stainless steel 0.01"(0.25 mm) from VICI.

Previously I had used PEEK tubing, but I highly recommend using SS precut electropolished tubing because:
-PEEK will fail at higher pressures (my experience, especially if it is exposed even only once to acetone or other solvents that may be used for cleaning the system)
-Home-cut stainless steel will have rough edges leading to dead volumes

http://www.vici.com/tube/cust-met.php

If you want I can provide you with the lenghts of tubing needed

[bunnahabhain]

Previously I had used PEEK tubing, but I highly recommend using SS precut electropolished tubing because:
-PEEK will fail at higher pressures (my experience, especially if it is exposed even only once to acetone or other solvents that may be used for cleaning the system)
-Home-cut stainless steel will have rough edges leading to dead volumes

http://www.vici.com/tube/cust-met.php

I never had problems with peek up to 380 bar, and if it fails it is easy and rather cheap to replace. To be honest, I used PEEK as a cheap option to see if I see some benefit at all. I did, and therefore I leave the PEEK as long as it does it's job
I am also a big fan of the VICI steel capillaries, I won't ever buy others.

If you want I can provide you with the lenghts of tubing needed

That would be great, especially for the ones leading to and back from the dampener.
Thanks a lot
Jörg

[Klaus I.]

I’m not sure about the application you have in mind. Do you really want to reduce the gradient dwell-volume or do you want reduce the extra-column volume as it is described in the article?

Of course it makes sense, to reduce the extra-column volume by using smaller capillary diameters downstream from the injector. All of my systems were installed that way. But I was never thinking about the capillaries between pump and autosampler (I work usually with flowrates > 1 mL/min). It is very interesting if there are observable differences.

I’m also curious about the optimization of the gradient dwell-volume. The 1100 dampener volume depends on the system pressure. By using smaller capillaries the system pressure will be higher (forth-power relationship). Unfortunately I have no access to the data of the 1100 binary system, which was optimized that way in the past.

Concerning the extra-column volume: Are you aware about the reduced-volume heat-exchangers which were available since the introduction of the 1200 SL system?

Hm, what is the current recommendation for the flow-cell. Is it still the 2µL high pressure flow cell?

Best regards
Klaus

P.S. I’m a big fan of the Dionex Viper capillaries ;o)

[Himar]

You can also try bypassing damper and mixing chamber completely.

[mattmullaney]

Hello All:

Just small stuff to add, you folks have everything well in hand already.

@ Klaus I., I'm not sure about the 1200 SL, but for the 1260, yes, 2 microliter, 400 bar cell is recommended.

http://www.mac-mod.com/pdf/technical-re ... Report.pdf

http://www.mac-mod.com/pdf/technical-re ... uceECV.pdf

You guys know this stuff already...the Mac-Mod tech reports offer good summaries.

@ bunnahabhain, I'd probably keep a 0.17 mm ID "green line" on this one...in any case, I don't think that this capillary ID will make a great deal of difference for what you're trying to do. Please, if I'm wrong, feel free to correct me on this point.

VICI capillaries are very good, quite agreed...haven't had the chance to try out Viper capillaries.

[bunnahabhain]

Dear all

what I am trying to do is really to get the gradient to the column as quick as possible. I know I cannot turn a 1100 quaternary pump into a binary 1260 or so, but for low flow rates, the gradient performance is, well, useless. I have an inter-lab validation study which was validated at 0.2 mL/min (using a binary pump, of course) and I just can't get the retention times stable. I guess the problem already starts in the mixing chamber, which is too large fur this flow rate.

Kind regards
Jörg

[Klaus I.]

Maybe it is a problem of the low pressure pump in general. With this design the gradient can varied only every full pump-stroke. For low flows and rapid gradients the short-time accuracy of the gradient-mixture is not given.

Best regards
Klaus