change the column gc/ms without stopped turbo pump

Hello !!

I have a question.
how I can change the column in the gc/ms without stopped turbopump ? It is possible?
regards Azrael ?

Parents
  • Use 1 meter of deactivated fused silica tubing going into the source (the same diameter of your column), then use a union (either the press-fit glass type of, better yet, the SilTite brand) to connect to your column in the oven. When you want to change columns, cut the fused silica just after the union and plug it with an old septum while you do the change. Then affix the new column to the union and finally remove the old septum, cut a few mm of the fused silica to remove the rubber plug, clean and affix to the union. Done. I have been doing this for 30 years and it has never failed me. 

     

    Or you can go the expensive way and purchase the Agilent Quick Swap attachment. I have no experience with this, though.

Reply
  • Use 1 meter of deactivated fused silica tubing going into the source (the same diameter of your column), then use a union (either the press-fit glass type of, better yet, the SilTite brand) to connect to your column in the oven. When you want to change columns, cut the fused silica just after the union and plug it with an old septum while you do the change. Then affix the new column to the union and finally remove the old septum, cut a few mm of the fused silica to remove the rubber plug, clean and affix to the union. Done. I have been doing this for 30 years and it has never failed me. 

     

    Or you can go the expensive way and purchase the Agilent Quick Swap attachment. I have no experience with this, though.

Children
  • Gentleman,

    The above statements are correct & I would like to point out here from my experience as a service engineer:

     

    1a) Azrael is probably responsible for several users

    1b) many "modern" users do not come with our practical experience.

     

    2) Pressfits are good, but in my opinion not suitable for less experienced users or GC novices =>

           then metal ferrules like AT CFT (Capillary Flow Technology) or Siltite are the better/more reliable choice.

     

    3) Short MSD restriction capillary:  can I use any dimension? Please, NO

       Why are the dimensions of the MS restriction capillary so important?

          When the main column is removed, only the restriction capillary (inside the MSD) limits the air flow into the MSD/pump.

          The dimensions of this capillary (iD & L) should be calculated, because more than 6(-10)ml into the MSD/pump should be avoided !

     

    Examples for bad & good AIR flow values by restriction capillaries (no gas supply by EPC or main column):

    Result/summary

    Dimensions of restriction capillary [ID µm * L]

    Air Flow into MSD,

    (without main column)

    Idea: where & who to use?

    (not mandatory to do)

    BAD, too high flow

    250 * 1.0 m

    14 mL

     

     

     

     

     

    OK

    250 * 2.5 m

    6 mL

    if main column has ID 250µm.

    extend the main column by 2.5m

    OK

    200 * 1.0 m

    6 mL

    if main column has ID 200µm.

    extend the main column by 1 m

    Calculation details: see screenshots below

     

     

    Finally:

    Because of all these mentioned uncertainties I always recommend the Agilent QuickSwap.

    Admittedly, QuickSwap might be not cheap (because of EPC) but in the environment of many users it’s the SAFEST hardware choice and it also protects expensive equipment very well.

     

    Note: when changing columns the ion source/quad temperatures should be reduced to 100°C to avoid unnecessary oxidation.

     

    regards, M.

     

  • Yes, those are very good capillary tubing unions. Or you can use these:

     

    5190-6979 | Agilent 

     

    They will be cheaper from other suppliers...

  • Hello ,

    yes, that was my intention. Thanks for the good explanation 

     

    regards, M

     

  • Good points. I agree that the quick-swap is the best solution if the expense can be justified. As to press-fit vs metal ferrules, it's a hard decision. They both require care on the part of the person doing the column swap, and the ferrules cost twice as much as the press-fit. One has to find what works best for the situation.

     

    I do have one comment in regards to item 3:

     

    I have never considered that final length of capillary to be a restrictor, but an extension to the column (making sure that it's the same ID as the column). Then I just add the length of the capillary to the length of the column in the column definition and the EPC takes care of keeping the flow rate at the desired value. Not that it will make a major difference in any production environment. As long as you get the chromatographic resolution and run length that you need/want, the actual flow rate should be irrelevant as long as it's within the instrument's capabilities. The 14.5 mL/min are the maximum that the 1 m length of 0.25 mm capillary can transfer, but that volume isn't available because the EPC is controlling the flow from the column, so it's only that much volume that gets into the MS.

     

    Cheers,

     

    Milan.

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