By Anonymous on Thursday, April 15, 2004 - 06:54 am:
I am running a SEC HPLC method with RI detection, and I am seeing that during system suitability injections, the first injection of the five replicate injections of the working standard is always very high. The next four injections are very close in
area counts. The current injection format is to inject 2 blanks, 5 working stds, then 1 check std. The mobile phase is 70% 100mM phospahte buffer/30%ACN, using a SynChropak GPC column isocratic, and the sample is a natural polymer. Does anyone have any idea what could be causing this? The blank injection is the mobile phase (sample solvent as well), but the standard contains 50% MP and 50% water as the solvent. Could this be causing the initial differnece?
By Anonymous on Friday, April 16, 2004 - 09:28 am:
Do all 5 of your injections come from the same vial? If so, there could be pressure in the vial that is pushing "extra" sample into the loop. After the septa is punctured, the pressure has somewhere else to go.
By Anonymous on Monday, May 3, 2004 - 07:00 am:
Thank you for your input. Yes, the injections are all from the same vial. I will investigate this further.
By Henrik Vogelius on Wednesday, May 19, 2004 - 10:42 am:
If you move on to vial 2 and repeat what you did in vial 1, do you then get the same result then? Normally this is why you do a blank run.