Agilent 5973MSD Air Leak

[djletin]

I'm having a difficult time troubleshooting a signiifcant air leak on 5973MSD. Noticed significant N2 and O2 in leak check diagonostics. Needed to change columns any way, so vented. Installed MSD inteface nut with no-hole ferrule only and pumped down. Leak check good (<2% 28(N2 abundance). Vented again. Installed column to MSD inteface nut with inlet end of column plugged to isolate it from potential inlet leaks. Pumped down but get VERY high 28 (N2). Sprayed dichlorodifluoromethane on MSD interface fitting and monitored m/z 85. but none detected. Where could air leak be coming from?

[JI2002]

Is is possible the column was broken?

[djletin]

Is is possible the column was broken?

No. I checked that. Also tried same this morning with another column I had just taken out of another GC-MSD that was working. Same symptoms.

[AICMM]

djletin,

Very high 28 AND 32, right? Possible that the MSD nut is stripped, possible that the ferrule is installed the wrong way? Possible that the ferrule is cracked? How did you plug the inlet end of the column?

Just some thoughts.

Best regards.

[djletin]

djletin,

Very high 28 AND 32, right? Possible that the MSD nut is stripped, possible that the ferrule is installed the wrong way? Possible that the ferrule is cracked? How did you plug the inlet end of the column?

Just some thoughts.

Best regards.

Plugged inlet end of column with septum. Was thinking either MSD nut stripped or perhaps theads on transfer line damaged. Will try to repeat making sure I use brand new MSD nut.

[BCBC]

I have used a "die" to correct cross threading on the interface. Also toss out the old interfacen nuts since they may be misaligned.

[Consumer Products Guy]

I'm sure you remembered that the ferrule at the MSD interface is positioned "backwards", correct?

[Rick]

I suspect gas tank contamination....change the gas tank, wait 30min for clear old gas and check again.

[bhuva31]

Possible reasons for poor resolution:
1. contaminated mass spectrometer,
2. poor mean free path i.e. poor vacuum,
3. wrong tune files i.e. the tune parameters are not matching with current instrument parameters.

Isolate the leak as nitrogen or moisture and look out for the nitrogen:oxygen ratio, in general 3:1 or 5:1 indicative of air leak. If nitrogen dominates suspect contaminated gas filters.

If isolated MSD had leak, look out for damaged O rings at vent, side plate, vacuum gauge manifold, CI connection.

If GC had problem, look out for aged septa, leak at liner nut, injector nut, detector nut and contaminated gas filter.


The Agilent mass spectrometer calibrated using perfluorotributyl amine (PFTBA) using masses 69, 219 and 502 m/z utilizing Mathieu stability diagram.

Among the tunes two are important on the basis of sensitivity – autotune and resolution – standard spectra tune with difference in peak width of 0.6 and 0.5 respectively. In general, the auto tune itself the trading off between sensitivity and resolution.

Happy MSD days