Chromatography Forum

Hello All,

We have an Agilent GC/MS 7890A/5975C running in PCI mode with isobutane that is giving us some grief. In a previous post, I indicated an intermittent "step-like" baseline disturbance and short filament lifetime. We thought we fixed the issue after swapping the repeller insulator on the source, but the issue returned with a vengeance and we are now experiencing a complete failure in some part of the CI module that is preventing operation in CI mode. We get the error message "CI Flow Controller is not controlling reagent properly" for both methane and isobutane, and a flow and pressure reading of -1. It is running beautifully in EI mode.

Our independent service engineer (we do not have a service contract with Agilent) thinks the issue is the mass flow controller. However, because the CI module has been upgraded, Agilent no longer sells the mass flow controller we need. They have indicated our only option is for Agilent to come replace the entire CI module. Our module is only five years old.

We are hoping to try some alternative options before throwing out the baby with the bathwater. We are not 100% sure it's the mass flow controller, since we don't have a replacement part to test. Any ideas for what else could be going on, and how we could test it? Could it possibly be a failed valve or gasket? Also, any suggestions for reputable sources for used parts? Would be it possible to buy a mass flow controller from a third party, or is compatibility strictly limited to Agilent's products?

Thank you, I know this is probably a reach. Let me know if I can provide additional information.

An update.

We happened to have a mass flow controller from an old CI module that was compatible. We swapped it, still getting the same error. So unfortunately, the mass flow controller is not the issue. We also blew out the gas lines in the CI module, none of them were clogged or had any debris. Next step is to swap out the shutoff valve and motor. If this doesn't work, I fear we have an issue with the CI flow control board, which Agilent no longer sells. If anyone has any other suggestions, please let know.

Thank you!

Hello, I'm curious whether you were ever able to solve this problem. I'm getting the same error on our 5975C. At first it was only happening when we used gas B (isobutane) and after confirming that we had no problems with low pressure or flow restrictions upstream of the CI flow controller, I plumbed the isobutane into the gas A position and the instrument ran without problems for about a month. My understanding is that there is a single mass flow module downstream of the reagent gas solenoid valves so my assumption was that our gas B valve was not operating properly. However, after a vent/pumpdown cycle we now we see the same error on the gas A line as well and I am suspecting that either the mass flow module or the CI controller board is faulty. As your posts are the only mention I've found of someone experiencing this problem, I thought I'd reach out to you before going any further.