%RSD Failing issues

Ravihans

Dear team,

I am facing %RSD failing problems in HPLC waters systems which leads to bracketing failures. Can u guide me  what precautions need to take before to start of analysis. 

We observed that due to RT change only %RSD failures happens.bubble found on compression observed on display in log.  We are taking all the necessary precautions while  doing the analysis. we are not performing manual purge injector . Is it required? 

Please help me to sort-out the problem.

Dan_Ramlose

Degas your mobile phase, make sure ALL of your lines have degassed mobile phase or other eluent in them, go ahead and purge the injector once or twice before starting your run and be sure that your needle and seal wash has not run out.

If you do all of that and still have problems, look at your retention times. If they vary much, you probably have a sticky check valve that needs replacing. If that is not a problem but RSD is still high, try a compression check. If it fails, get the unit serviced.

Ravihans

Dear Dan_Ramlose, 
Thanks for your reply. can u clarify that is it required to do manual purge injector ? if yes how much sample loop volumes should i give ? 
These kind of issues occurring very frequently in every week. In order to revise SOP, can u please tell about manual purge injector is necessary for high injection volume methods? 

Dan_Ramlose

I usually put a Purge Injector direction in my sample set method and just use the default settings. I think it takes 10 minutes for a 2695.
If doing it manually, the number of loop volumes depends on how "sticky" your analytes are. For clean, easy to wash out samples, 5 volumes should be fine. If you see carry-over, you need either more volume or more purge cycles (or both).

MarcNoble

Hi Ravihans - Maybe start by checking out these KB articles about "bubble found on compression"

Good Luck!