Split flow prior to MS: flow rates used

<p>I want to increase the flow rate on my acquity methods from 0.3ml/min and think splitting the flow post column prior to MS would do the trick.</p><p></p><p>Does anyone use flow rates above 0.3ml/min on an Acquity?</p>

Answers

  • Hello:

    What is the mobile phase and column dimensions. It is hard to comment without this, just to be on the safe side.

    Liz

  • The column is BEH C18 1.7uM 2.1x100m. The mobile phase is methanol:water 0.05% TFA

  • Hi there,

    I was just wondering what you are trying to achieve by increasing your flow beyond 03mL/min. Without knowing what you are trying to achieve with your chromatography I can't really advise you on what would best fit your requirements, only on what I have used and found successful in the past.

    Typically, I have used between about 0.4mL/min and 0.6mL/min for 1.7µm, 2.1 x 100mm ACQUITY methods, although for a full view of what is feasible for all of the column types id found in the ACQUITY UPLC BEH Columns Care and Use Manual (see page 8 for a table of recommended flow rates and associated backpressure for different column types).

    Without knowing which type of MS instrumentation and what type of ionization you use, however, it is very difficult to give you a definitive answer that will be relevant to your situation on whether or not to split into the MS.

    Still, saying that, most major manufacturers' recent MS instrumentation will have no problem taking 0.4- 06mL/min flow rate of a methanol/water mixture directly into the ESI source (although with certain source designs, you may need to increase the temperature used to desolvate the eluent stream), APCI will certainly have no problem taking that level of flow, however, if you are using APPI, you may wish to keep the flow rate to a minimum (typically 100-200µL/min is optimum for APPI) or split post column. Just bear in mind however, that a post column split will almost certainly introduce dead volume and/or turbulent mixing into your flow stream, hence potentially degrading the chromatography before your analytes reach the MS, still it may be something worth trying for APPI.

    Apologies for not being able to be more specific, hopefully though. this should have given you a useful starting point for getting to where you need to be.

    Thanks and all the best,
    Ed

  • Thanks Ed,

    My rationale was to decrease run times. I have been carrying out complex metabolic studies and hence have sample run times in the region of 30 to 60 mins, I know this sounds like an awful long time especially using an acquity but I have found that by increasing methanol conc at the start of the gradient I am in danger of losing some of the most hydrophilic metabolites in the solvent front.

    I thought that by increasing the flow the metabolites would elute earlier, although not too early, and hence I could reduce my run time.

    I am using ESI on a quattro premier. Would this system cope with 0.6ml/min without the need to split the flow, but with increased desolvation temp?

    Thank you for the link to the resources I will have a look at them.

    Regards

    Jason

  • Not a problem Jason,

    The Quattro Premier should be able to cope with 0.6mL/min without split, although I woudl suggest using at least 350°C for the desolvation temperature and between 130-150°C on the source temperature to aid the desolvation process as much as possible. A good starting point fo the desolvation gas would be around 800-900 L/Hour as well.

    Hope this helps you to get your methodology to where it needs to be.

    All the best,

    Ed

  • Thanks Ed,

    I will give that a try, makes sense.

    Thanks again,

    Jason

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