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- Posts: 15
- Joined: Wed Feb 15, 2017 6:29 pm
Proposed methods: external calibration or Standard Addition.
Short background: The gas is not readily available at ≥99.95 mole % from any vendor. We purchase this gas from random sellers, process it to clean it up, and send it to a 3rd party vendor to certify it's purity. Sometimes it's beneficial to know the purity mid-processing and I would like to calibrate our GC-MS properly to do this. The range of mole % we typically work with and see is between 99.95 to 98.00, and 99.60 is the minimum we can send to production.
My initial thought is to use several of the certified samples we sent to our 3rd party vendor already, run it through our GC-MS, and create a calibration curve from those. I'm skeptical of that idea because I know I can send two samples of gas from the same batch, on the same day, and receive a variation in purity (+/- 0.05 mole % typically), but it might just be the nature of the beast... and I also feel like I leave a lot of room for error because I don't know if all of those samples were run on the same conditions, GC, etc...
The standard additions method would still require me to use a high purity sample that has been certified from our 3rd party vendor.
All comments, questions, and recommendations are gladly welcomed!