what can we do to improve internal standard counts consistency? since sometimes RSD% for internal standard counts were beyond 5%?


. 1. recently, we changed the tubing for internal standard and sometimes found, RSD% for internal standard counts was beyond 5% which raises red flags ( see the below picture) 

2. These warnings showed once after 6 or 9 injections.  we noticed some very small bubbles were created and accumulated when the sampler was rinsing. 

3. what should we do to make internal standard reading consistent? 

Thank you

Best regards, 

DI Xu 

  • Hello  

    Thanks for your posting this question in the Communinity.

    Are you using ISIS3? In this case, you can increase the speed pump  around 40-50% and rinse time to 20-30 sec.

    If you are not using ISIS, please check the connectors and tubing on Rinse port .


    Best regards

  • This could be related to mixing since you are only seeing it sporadically. Other than confirming the condition and tension of your tubings.

    Other Things to try:

    1. If you do not have ISIS or some other valve system (i.e. PrepFast, etc), in your Hardware Dashboard under Sample Introduction, go into Special Process for Sample Change and check the box under when ALS Probe Move that says "Stop Peripump Rotation". This will help prevent any dead volume in the T and encourage better mixing for each sample since the I/S. conc will stay more consistent. If you do this, you CANNOT use preemptive rinse in your batches. 

    2. Try adding 0.1% Triton X-100 to your internal standard solution. 

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