loop offline or online?

Neuchuplc
Neuchuplc
in Instrumentation and Mass Spectrometry
<p>Hello,</p><p></p><p>I have a few questions regarding the way the Acquity injector works.</p><p></p><p>1. During normal injection mode (no load ahead), does the mobile phase flow through the injection loop during the whole run or does it go to offline (load) position after a certain time? I think it stays online during the whole run but I am not entirely sure.</p><p></p><p>2. In load ahead mode, when working in partial or full loop, one needs to set a time after which the injector gets offline. I understand this time should be long enough to enable high organic solvent to go through the loop. However I guess it should be short enough to enable the next injection load to occur within the run. So my question is: how much time before the next injection should the injector be set offline?</p><p></p><p>3.In partial loop with needle overfill mode, one doesn't need to set this offline value. Do you know why? Does it mean that in PLWNO mode, the injector automatically switch to offline position after a certain time?</p><p></p><p>Thanks for your reply.</p>

Comments

  • rune
    rune

    Hi Geatan

    Reg. Question 1: Yes the loop stays on-line with the pump for the entire runtime.

    Reg. Question 2: The loop off-line time should be long enough to enable the sample to be flushed from the loop onto the column. I usually say 10 times the loop volume, but if you have sticky samples you might need to wait longer. The next sample will not be loaded until approximately 30 sec. before the end of the run anyway (depending on injection volume and loop size).

    Reg. Question 3: In PLUNO mode the injection valve cannot switch to off-line before the run has finished. In this mode the sample is drawn to the other side of the injection valve BEFORE the valve turns to load (loop off-line) position. So in load ahead mode the next sample is drawn to the other side of the injection valve during the previous run, and when the run is finished the injection valve turns to load and the sample is pushed into the loop and the injection valve switches back to inject.

    I have attached some graphics that might help explain what happens.

    best regards

    Rune

  • Neuchuplc
    Neuchuplc

    Thanks Rune, it is all clear now.

    Best regards,

    Gaetan

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