Chromatography Forum

Hello All,

I am facing a very troublesome leak issue but struggling to pinpoint the source of leak. The GC component is working fine, its holding carrier gas flow and gc column pressure fine. But when I try the auto startup, it does not trigger the rotary pump to start, neither does it start the turbo pump or the ion source. If I do it manually, the rotary pump pressure goes down to 2 Pa, then I turned the turbo pump on, the pressure went to 3e-4 Pa. Now here comes the issues:

1. There is bubble forming in the rotary pump oil viewing window.
2. The instrument passes the auto tuning
3. The ion source temp goes upto 230C which I can see in the software's window but GC panel shows the temp to be zero.
4. There is no loud noise coming from the turbo pump.
5. Since it passed the auto tuning, I tried collecting background scan, GC would start running but mass spec status stays at "Ready" but it doesn't collect any scan.


I suppose the bubbles forming would indicate a leak but I don't know where that could be coming from, I even tried using a Helium detector around the instrument and found nothing. Please let me know what steps I can take now. Thank you

Hi Tasneem,

your vacuum readings seem ok, so there is probably no leak in the MS.

I don't know why the GC panel shows the wrong ion source temp, but as long as the software gets it correct this should not be a problem.

The turbo pump shouldn't make a loud noise - if it did, it was broken.

You should check your method if the instrument doesn't collect mass spectra. What are your start and stop times set on the MS-tab in the instrument parameters?

For the bubbling oil: open the gas ballast valve for an hour or so. If that doesn't help, change the oil.

Kind regards, Hartmut

Thank you Hartmut.

I was wondering if there is any command i can provide to mass spec to start other than just starting the run? Our instrument is a hyphenated technique, it is connected with a py unit, normally the process starts from py and it triggers gcms start. Now that we are trying to troubleshoot it, we have separated the connection with py.

Now when i start a single run in gcms, gc starts but mass spec stays at "Ready" status like I mentioned in my previous message. Is there any way i can send "start" signal to mass spec? In my method mass spec is supposed to start after 1 minute. But it doesn't start at all.

My auto tuning results are fine and vacuum is also fine.

Ok, so the MS doesn't get the start signal. There is an RS232 cable connecting GC and MS. Maybe this was connected to you "py" (Pyrolysis?) unit and has to be re-connected to the GC?

Don't you have the phone number of a Shimadzu service tech? They are usually very helpful...

Yes, I have been in contact with shimadzu. They have been very helpful.

So now I have connected everything and ran a blank through the py. The same thing happened, py triggered gc start but ms didn't start.

The fact that ms works fine when its there just by itself during a real time mass spec run, I wonder if the ion source temp at the gc panel is the reason ms is not getting triggered to start.

GC panel shows that ion source temp is 0, but again the software shows it 23 when i shut off the vacuum but when i turn it back on, it goes back up to 230 (the set temp for my method). So, i guess the thermocouple is working fine but something in the gc panel is off. Any ideas how i can fix that?

Thank you
Tasneem

So, the MS doesn't get a start signal from the GC.

Like I said before, this could be a problem with the cable connection between the two devices.

I don't know if the incorrect temperature displayed by the GC is the reason for this problem.

Both problems might be due to a faulty configuaration. There are two menu items (on the GC panel, after pressing the [Func] key):
6. GC Configuration, and
7. Service/Maintenance

Normally the correct values there are set at installation time of the instrument. Maybe something is accidentally wrong there. I don't know enough about the options that can be set there to advise you what to do exactly. Reading the manual might help...

Another option might be a firmware update or re-install.

Okay, shimdazu came to my rescue. Adding the solution here, in case anyone else faces the same problem. The RS232C cable settings needed to be changed.

It is actually a bit confusing, even thought GC uses a USB cable to connect with the computer but the RS232C cable provides the ion source temp info to the GC panel.

But also be careful once you change the settings in the cable (GC panel-Home-Function-Transmission setting-RS232C-(Level 3, baud speed 115200), remember to apply the setting to USB so it connects with the computer again.

Thank you
Tasneem