HP 5970B will not perform TUNE

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

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I have a 5970B attached to a 5890 GC that was last tuned perfectly in 2002 (no column/carrier gas - mass spec transfer line end sealed with nut and blank ferrule). It sat on the bench for twenty years in climate controlled room with rough pump never disconnected. The vacuum was comprimised because the flange nuts were not properly tightened.
After all these years, the turbo pump was oiled again and gave a vacuum of 2.5 X 10-6 torr (capped end transfer line) when pumped down. However now the system refuses to TUNE because of very poor sensitivity. The PFTBA peaks are two weak and are jagged and spit. The abundances are from the hundreds to 40,000 rather than the half to 1 million range.
After trying two old multipliers, I bought a brand new one which gave even poorer peak heights from 200 - 700.
Could this be an electronic problem with either the detector or quad board? The transfer line was set to 280C. Should the temperature of the heater tape around the manifold be checked?
Is your PFTBA vial empty?
I just checked and it is about 3/4 full. I added this PFTBA several months ago when first starting this. It is also 20 years old, but has been checked by FTIR which gave a perfect spectrum.
I would also like to add that this is being run on the Pascal Workstation which has Diagnostic software. I ran a BASIC SYSTEM TEST and all checks including the RFPA and EMV were all "OK".
The age of the instrument should not be an issue so long as you still have access to the previous set of working MS tune parameters. These systems are inherently stable and will at least generate spectra using a previously good set of tune parameters,

As with any HP / agilent MS, the amu width and gain plus mass width and gain parameters are an important first step to verify . Access a good tune file and in manual tune, cross check the values of these 4 parameters and adjust if necessary.
I saved the Tune print-out from 20 years ago and all TUNE values are the same. It is using the original computer/software.
However after the question about "empty PFTBA vial?" I had an idea. Ever since I have been working on this, each and every time I vent the system by loosening the column nut plug on the end of the transfer line. You can clearly hear the noise of the air as it rushes in.
Tonight, I went and tried doing this to the PFTBA valve end. The mass spec was off and cooled but still under vacuum. I removed the PFTBA vial and turned the Swagelok handle and I did not hear any air noise at all. I then went to the front transfer line end and turned off the column nut and could easily hear the air rush in.
Could the valve indeed be no good? I have noticed in the past that electronic PFTBA valves go bad, but would imagine a manual valve failure.
I will now check into this.
That is an important observation. For sure both manual and electronic PFTBA valves can become defective with blocked restrictors.
In the meantime you can still verify the GC and MS are working without tuning.
With the system vented and before reconnecting the GC column, check the GC inlet can deliver flow through the column by dipping the column end in a beaker or tube of methanol or whatever solvent you have on hand. watch the stream of gas bubbles to confirm column gas flow.
Reconnect column, pump down MS, restart Pascal controller. If you have a high vacuum tube installed, monitor MS vacuum. Allow system to stabilise with GC oven at 100'C , inlet at 200'C and a column flow of 1ml/min, split @ 100:1
In the manual tune screen, change the MS scan range from 10 - 100 amu.
Possibly you will see responses for water and air at m/z 18, 28, 32.
However of real interest is to manually inject 1uL of solvent headspace vapour.
Depending on the length of the column with the MS scanning , you will observe a large response after approx. 1 minute. Methanol gives a spectrum at m/z 31, acetone at 43 and 58.
When you know the MS is operational, you can focus on the PFTBA valve.
I've only gone back as far as a 5973 but I would think that the PFTBA valve should be closed unless tuning. Easiest way to check would be to open up manual tune and actuating the valve from there.

I'd heat the oven up to max run temp and just scan out to 500 and make sure there isn't a bunch of oil in in analyzer chamber. I revived an ECD that was sitting around for 8 years at ambient and it took a day at elevated temps and flows to bake all the garbage that accumulated on the detectors. How long was it pumping down for before you tried to tune?
mathiue and 70ev- Thanks for your input. I have removed the analyzer at least 5 times to change filaments and multipliers and every time I let it pump down for at least 1-2 days before making an initial test. It was then left on for 2 - 3 weeks before shutting off and the baselines were consistent - even when the peaks were in the 300 height range baseline is good. I also make ion guage readings each time.
I pulled off a valve from a junk analyzer and upon observation was surprised how small the restricted side is. You will need a dissecting microscope to really examine it.
Introducing a test solvent from a column is a good idea. I will have to order more supplies (column nuts, gold seal, ect.) Right now the GC has only been
used to provide the connection to the transfer line DET B set to 280C. The GC temperature readings communicate perfectly with Chemstation.
I will start to order supplies and will try to find a new valve.
70 eV wrote:
I've only gone back as far as a 5973 but I would think that the PFTBA valve should be closed unless tuning. Easiest way to check would be to open up manual tune and actuating the valve from there.

I'd heat the oven up to max run temp and just scan out to 500 and make sure there isn't a bunch of oil in in analyzer chamber. I revived an ECD that was sitting around for 8 years at ambient and it took a day at elevated temps and flows to bake all the garbage that accumulated on the detectors. How long was it pumping down for before you tried to tune?


5970 valves are manual, so have to switch them by hand instead of in the manual tune.
The past is there to guide us into the future, not to dwell in.
lsmith wrote:
mathiue and 70ev- Thanks for your input. I have removed the analyzer at least 5 times to change filaments and multipliers and every time I let it pump down for at least 1-2 days before making an initial test. It was then left on for 2 - 3 weeks before shutting off and the baselines were consistent - even when the peaks were in the 300 height range baseline is good. I also make ion guage readings each time.
I pulled off a valve from a junk analyzer and upon observation was surprised how small the restricted side is. You will need a dissecting microscope to really examine it.
Introducing a test solvent from a column is a good idea. I will have to order more supplies (column nuts, gold seal, ect.) Right now the GC has only been
used to provide the connection to the transfer line DET B set to 280C. The GC temperature readings communicate perfectly with Chemstation.
I will start to order supplies and will try to find a new valve.


The orifice will be very small, it is there to prevent the liquid from being drawn into the analyzer, only the headspace gas should enter and in very small amounts, so that is probably good.

Another test you could try would be to loosen the inlet cap with blank ferrule and allow a small amount of air to enter, then retighten it and after 5-10 seconds scan and see if the air and water peaks are present.

The only problem with some of these very old MS would be the condition of the capacitors on the boards. If you can pull the boards and look at the ends of the cylindrical capacitors, look to see that the ends are flat and not swelling outward.

When you get the low response with the PFTBA open, does it give sharp peaks with low heights or just noisy grass peaks where the peaks should be?
The past is there to guide us into the future, not to dwell in.
James_Ball wrote:
70 eV wrote:
I've only gone back as far as a 5973 but I would think that the PFTBA valve should be closed unless tuning. Easiest way to check would be to open up manual tune and actuating the valve from there.

I'd heat the oven up to max run temp and just scan out to 500 and make sure there isn't a bunch of oil in in analyzer chamber. I revived an ECD that was sitting around for 8 years at ambient and it took a day at elevated temps and flows to bake all the garbage that accumulated on the detectors. How long was it pumping down for before you tried to tune?


5970 valves are manual, so have to switch them by hand instead of in the manual tune.


"Sorry for the delay but this is the first time I have been back. The PFTBA is a MANUAL SWAGELOK turn valve on the outside of the spectrometer and is only turned ON when I do a TUNE.
As far as the QUADS/SOURCE they look very clean - I have removed the analyzer 4 times to install 4 electron multipliers following guidelines strictly from the service manual. Also each time I let pump down for a full two days before turning the valve ON. I also check the vacuum first (2.5 x 10-6 transfer capped/ no column). I do not know how to attach pictures here - but if you looked at the PFTBA peaks themselves , even though they are weak and about 300 high - the baseline is not noisey - so is this an indication that the Quads are not contaminated?
I ws thinking that the 36 year old wick in the PFTBA valve may be comprimised. The only thing to do at this point is to change the valve or let air or solvent leak at the front transfer side to see if it will detect air/H2O/solvent ions."
Lewis
I would try introducing a small leak at the inlet first, just loosen the nut for a few seconds then tighten again, then turn on filament and scan and see if there is any residual 28,32, 18 showing up. If there is, then it could be the valve, though I have not seen those go bad before.

If there is no sensitivity even with an introduced leak, then at worse case it could be the EM power supply. Not easy to test that since it is at -1000V and higher, if you have the proper test equipment then that would be next, but don't use just an average volt meter on that one.

Examine the boards inside and look for an swollen capacitors, with this much age on the system those would be the first things to go bad.
The past is there to guide us into the future, not to dwell in.
Thanks for the advice - in the next month I will do exactly that and let you know what I find.

Lewis
Thanks Lewis
Please keep us updated. There will be insights of benefit to all GCMS users, especially in the area of FC-43 calibration valves.
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