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- Posts: 9
- Joined: Fri Sep 08, 2017 4:29 pm
I am fairly new to HPLC/LCMS, and I am currently working on method development on an Agilent 1200 Series HPLC and 6100 MSD that has not been in use for about 5 years. My goal is quantification of certain additives in polymers.
I create standards by making a stock solution and diluting it down to a range of 100-250ppm, and my calibration curve is linear. I have remade the standards about 8 times, and my results are not consistent with one another, they appear to be increasing for each concentration, but linear for the same run.
The same trend goes for actual samples that I run on the machine. There is a definite pattern of increasing peak area, more consistent than the standards, where they should all be the same.
I thought the problem initially was contamination of the needle, or some other carryover from the previous sample. I fixed the issue by adding a needle wash and a longer post-run purge of the tubing. This unfortunately hasn't seemed to fix the issue with my increasing standards.
Any suggestions to what my issue is?