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7820A Inlet Pressure Limit Variability

Question asked by icg-001 on Apr 16, 2020
Latest reply on Apr 17, 2020 by james_jenkins

Hi all, I’m doing GC method development for the quantification of nicotine using a new column. I have chosen a short DB-HeavyWAX (Part number 127-7112, 10m x 0.10mm x 0.10µm) for its temperature stability, polarity, and speed potential. 

I'm using constant flow in this method with a column flow of 0.56mL/min, so the inlet pressure will increase from 45.6psi at the start to ~75psi during the run. The problem occurs mid-way, as it appears our inlet is ‘capped’ at 60psi, which then reduces our flow to ~0.4mL/min.

I initially presumed that this may be the software limiting pressure due to the narrower column, but trialling it virtually on our other machine, the limit there is 100psi no matter what we do to it, and my method would be well within the instrument’s tolerance. Is it perhaps an instrument model issue? They’re both 7820As, but if they’re different gens perhaps?

Is there any way we can remove this 60psi limit on the primary instrument?