Problem with GPC/SEC Multidetector Triple Analysis

Hi Everyone! 

I am new to GPC and currently I am using a Agilent 1260 GPC/SEC Multidetector (LS, RI, and Viscometer) to measure the molecular weight of my standards and samples.

The software I am using now is a GPC software.

I have questions regarding calibration and the Triple analysis.

Firstly, if my standards already had information about the Mw, IV, and I want to do the triple analysis, do I only need to calibrate the system and then to perform the analysis? or do I need to do the universal calibration and column calibration before the analysis? 

Secondly, when I perform the triple analysis after the the system calibration, the red boarder in the pictures attached shown and I couldn't proceed the analysis even though I change the curve fit, do you know why it happened and how to fix it?  

  • Hello ZBH, 

    The first step to do before you can use the system to analyze samples is to perform the System calibration. This must be done using a single narrow standard of Mw between 100k and 200kda, with known Mp, IV, dn/dc, and of course the concentration. Make multiple repeat injections, up to ten for good averaging. This will generate the detector constants (K values) for all the detectors, and this further enables other calibrations to be performed. The red box around the results is a clear indication the system has not been calibrated and therefore the slope of the Mw response curve is partially negative. Follow the System Calibration with any other calibrations you desire for the specific samples you plan to run. 

    Hope this helps, 

    - Howard

  • Hi Howard! 

    Thank you for your answer, it helps a lot! 

    When you said inject signal narrow standard in up to 10 replicates, do you mean I should do the system calibration on all of these replicates? As far as I know, when you proceed another system calibration on different sample, the previous calibration will be automatically replaced? and what's the point of calibrating 10 same molecular weight samples? 

    Regarding the red box, since in this case, I created several "batch" of samples and run at different days, but they both ran at the same workspace. I use a Molecular weight of 70600 to calibrate the system, but when I use the Triple analysis to measure the sample (Mw ~ 229000, 260000, etc) from other batch, the red box appear, does that mean I need to do the system calibration at each batch even though they are perform at the same workspace? 

    Best regards,

    B

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