GC OQ - Inlet Pressure Accuracy

[J Sackett]

Good day,

Currently working on procedure for AIQ activities within cGMP-regulated, pharma, QC labs. All initial AIQ is performed by vendor, our organization is working to bring recurring OQ/PQ in house.

I have run into some difficulty in setting up a calibrated manometer to perform inlet pressure accuracy component of GC OQ. I have worked through several tubing configurations with the generic (Dwyer Series 475) manometer with no luck. Can anyone recommend a supplier for a pre-configured and calibrated manometer which is capable of connecting to Agilent fitting? Or, advise on any OQ testing performed, in place of pressure accuracy via manometer, to demonstrate that the inlet integrity (e.g. accurate pressure/flow)?

Testing would be on Agilent 6890 S/SL inlet configuration. I was thinking a combination of split flow, purge flow and column flow readings with a calibrated mass flow meter would demonstrate inlet flow controller/3-way solenoid/backpressure regulator are operating as expected - would this flow testing be comparable to pressure accuracy test? Thoughts?

Thanks in advance!

Cheers,
Jeremy

[CE Instruments]

Sorry but is this not overkill and a waste of time ? The head pressure supplied to your GC will not within a set of wide parameters affect the flow/pressure applied to the column. A simple gauge should be fine, is there any requirement for calibration and at what time interval ? Once the gas enters the GC it will be passed to the EPC module that will be programmed to give the desired flow/pressure as set by the GC. As part of the IQ the supplier should have carried out a set of tests and calibrations to confirm the instrument is within specifications. As part of any on going PQ/OQ you should ideally be using these tests or getting the vendor to check them as this will validate the instrument is still performing to the original specification ? I am amazed at the extents that are carried out (required ??) as part of these tests. One upon a time it was more than valid if you ran a certain test standard through a particular column using a set test mix and obtained reproducible results. This must be the best way to prove that any instrument is still performing to exactly the same specifications ? IMO repeated checking of a complete method with your standard is the best way to check GC performance.
If you are trying to test the pressure produced post the EPC module you ideally need to either do this at zero flow as any flow from the EPC will need to be controlled within the expected GC conditions. If you run a flow based method you can only check the flow at the end of your desired column as flow is controlled by the GC from the head pressure of the gas vs the back pressure of the column.

[J Sackett]

CE,

I believe you may have mis-interpreted my questions, apologies if I did not provide sufficient clarity.

I am not concerned with head pressure pre-EPC for qualification activities. Our gas supply regulators do have simple gauges, as you indicated.

The supplier (Agilent) did perform IQ and has typically been performing annual OQ/PQ activities as well. We are working towards developing procedures and executing these OQ/PQ events by trained staff, in-house.

Inlet pressure accuracy is a "Core GC OQ test" as defined by Agilent Equipment Qualification Plan. My difficulty lies in measuring the inlet pressure (post EPC) with a calibrated manometer as defined by Agilent procedure, e.g. configuration of tubing/Swagelok to connect manometer probe to inlet via a pressure tight setup has not been successful for me. To test the pressure post EPC the GC is programmed to defined inlet pressure via the keypad interface and pressure measures, I just need to figure out how to measure the pressure in the same manner Agilent does.

If other measurements, such as column flow, are an acceptable alternative to direct pressure measurement, I will need to provide sufficient justification for doing such. This is the approach I may take, since the pressure measurement has proven difficult.

Our quality unit seeks to maintain annual OQ activities similar to those performed/recommended by Agilent in which operational set points are defined, programmed and measured to compare against acceptance criteria to demonstrate the mechanical components of instrument are operating as expected. For PQ activities an evaluation of system performance under defined recurring test conditions, as you described, will be our approach.

Thank you for your considerations.

Cheers,
Jeremy

[Peter Apps]

The connection of the manometer to the inlet can easily be done with a needle through the septum and a vespel/graphite ferrule with an i.d. that matches the needle o.d. in a 1/16 inch swagelok, and then whatever tubing and size converters you need to get to the manometer. In other words do not worry about disconnecting any lines to the inlets and reconnecting them to the manometer (in fact I would say that this risks causing leaks). Alternatively - connect to the column nut using a short length of column and the swagelok as above.

Sorry I can't help with where to get a manometer.

Peter

[J Sackett]

Peter,

Thank you for your guidance! The manometer is already in hand, so I will just work towards getting the tubing/Swagelok configuration assembled as you described.

Thanks again for your consideration.

To a joyful and prosperous New Year!

Cheers,
Jeremy