multiple injections

<p><span>Hello, </span></p><p></p><p><span>is it possible to inject the same sample several times during a run? </span></p><p><span>Our kit (uPLC-UV-MS-ELSD) has an ELSD detector that requires calibration to ensure quantification of our test samples. Currently, we calibrate the ELSD using 4 standards eluting at different retention times. </span><span>However, as we are currently experiencing issues with this approach, we are wondering iwhether it would be possible to inject one single standard every few minutes during the same run. </span></p><p></p><p></p><p><span>Thanks, </span></p>


  • Hello,

    as long as you're using the acqutiy sample manager it is not possible - or you can alter the icop, what is very unlikely...

    But you can do this with a workaround:

    Take a high pressure switching valve, insert the smallest loop you can get (0.5 µl or lower volume) and connect this between sample manager and column inlet. You need a programmable pump, which fills the loop for some seconds with your desired standard solution after getting an event from sample manager switch 1 (programmed in the event table of the sample manager). Maybe 10 seconds later you use switch 2 to switch the loop into flow path for one or two seconds.

    Problem with this is you get with every switch a pressure drop and likely a noise in the baseline. On the other hand you can easily enhance the system to get what you want.


  • lizh


    Could you tell us a little about the issues and perhasp there could be other possible solutions.


  • BJ

    If retetention time is long enough, you can inject a few times with a run time much shorter than the retention time, except for the last injection where all the peaks will come out.

    Assuming a retention time of 10 minutes, inject 3 references with a runtime of 2 minutes, then inject a fourth reference with a runtime set at 12 minutes.

    All your peaks will come out in the last run, showing a nice profile or whatever you want.