Injector Pressure Problem

[Balderquell]

5890 FID
Split/Splitless injector with EPC
Column: 30m x .25mm ID x .25um film
Column Flow: 1ml/min
Split: 50:1 50ml/min (flow verified @ 40C)
Helium pressure from tank 60psi

I am running hydrocarbon analysis (C6-C35) with a broad range temperature program. The injector pressure can not keep up with the temperature program, however, and the flow begins to rapidly drop off throughout the run. I've noticed that the injector pressure can not be adjusted (manually or through chemstation) above 15.0 psi--clog, leak, or other is my guess. If it's a leak, it does not seem affected by changing temperature.

The instrument is in a good state of repair and has been running fine. I have noticed a gradual decline in performance with retention time shifts consistent with loss of flow/pressure.

I've cleaned the injection port, cut some column, cleaned split line and solenoid, and removed the injector weldment and backflushed it with solvent. Ferrules and o-rings are new. I've leak-checked every connection that is easy enough to access.

Any thoughts?

[Peter Apps]

Check the septum purge flow at various temperatures, and all the settings (including the maximum and minimums for any parameter that these can be set for. Is the maximum 15 psi pressure the maximum that you can set or the maximum that you get ?

The only thing that you do not mention checking is the septum - this is the most likely source for leaks, and the most likely to leak at a high pressure and seal at a low one.

Peter

[Balderquell]

Septum is new.

And 15.0 psi is the maximum programmable set point. If I attempt to change the set point to 20 psi for example, the set point remains unchanged at 15.0. The set point can be adjusted to anything below 15.0, just not above 15. I've tried reducing the pressure set point to 5.0, allowing it to stabilize, and then increasing the set point to 15. The pressure rapidly adjusts to 15.0 and stops. The increase in pressure from 5 to 15 seems to go fast and without much difficulty.

[GasMan]

At the back of my mind I seem to remember that there may have been a low pressure version of the 5890 EPC introduced. This was for customers who needed to work with short 530 columns. The standard version was not able to control so well at low pressures.

Gasman

[Balderquell]

Gassman,

Makes sense to me and may likely be the case. But I called Agilent and they claimed they produce(d) only one standard version of the epc. Remember if the low pressure epc might have been a custom job?

[GasMan]

I can confirm that there was a 15 psi max pressure version. You will need to change the sensor board, which had the part number 19245-60025 for the 100 psi version. I am not sure if this is still available from Agilent.

Gasman

[GasMan]

More info.

There were two flavors for the EPC module, a two channel version and a six channel version. You probably have the six channel version, and the 15 psi max pressure was only available on the six channel version.

Gasman

[Balderquell]

You're correct, Gasman. This GC is using the 0-15psi sensor board.

Part ordered and on its way. Thanks!