Read Energy Test MassLynx4.1

<p><span>Hi,</span></p><p><span>We´ve a question about the Read Energy Test in MassLynx 4.1, because we want to use this as a functional test, with an acceptance criteria.</span></p><p><span>If we perform this test we get the following result (f.e. Wavelength: 187,1042): approx. 630 counts. How can we interpret this result? How long you can use this lamp? Is there a limit of counts we should not fall below?</span></p><p></p><p><span>Thanks!</span></p>


  • Hello:

    I discussed your questions with the Global Support manager for Optical Detectors

    I would strongly discourage the use of the read energy diagnostic as pass/fail criteria of the detector. This is because the detector has the ability to set the exposure automatically for optimal detection and because each assay is different in it's requirements for acceptable signal.

    For example it would be possible to replace a lamp that has abundant energy for most assays prematurely.

    It would also be possible just using the read energy diagnostic to misdiagnose a flow cell problem as if it were a lamp issue.

    The only way that the read energy diagnostic would be useful would be to record the values from when the detector is new at wavelength 230nm (at this wavelength the deuterium lamp has the most energy) and track the energy value at a 5 msec exposure until the signal becomes unacceptable for your typical separations. At this point the lamp could be changed, but it would also be critical to compare the energy of the new lamp from the flow cell to a shunt flow cell to avoid confusing cell problems to optical degradation (optics bench versus flow cell mechanics).

    The diagnostic was created to ensure that there was sufficient signal, although counts are reported the diagnostic was not mean to be quantitative, but rather qualitative.

    Therefore, best practice says to use a signal to noise value limit, using a given method, mobile phase, flow rate and injection peaks is probably far simpler and more meaningful.

    I would also add tracking the values for auto-exposure for a given set of samples where issues have arisen is very valuable, for a given method and set of samples the auto-exposure determined should not change.

    We hope this helps.