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- Posts: 2
- Joined: Wed Oct 06, 2021 2:21 pm
For setup of my samples, I measure out 0.5g of NaCl, pipette 3mL of sample, 0.1mL of internal standard (2-ethylbutyric acid 1800mg/L), 0.2mL 2M H2SO4.
The method of running - Headspace oven temp - 100C, Sample Loop Temp - 185C, Transfer Line Temp - 190C. 15min equilibration, 0.5min injection. Starting GC oven temp 60C, Ramp to 190 in 15min and hold for 2min. Post run is 230C for 2min.
We are running a DB WAX UI column. I calibrate from 5ppm-300ppm. When a brand new sample loop and injector are installed, things look great. After about 1month of running, I start to see some carry-over occasionally. Now it's been over 3months and my acetic acid peaks look all over the place. I have tried running the calibration from high to low (I usually go from low to high), extra DI blanks. Nothing seems to be helping. The peak shapes themselves look fine, I just can't seem to get anything to stay stable.
Any help would be greatly appreciated! Thank you.