LECO 4D GCXGC-TOFMS mass calibration failed

[mcqian]

Hi,

We recently obtained a used LECO 4D GCXGC-TOFMS. The system was last used in 2009 and was sealed when we obtained it. I get a very good vacuum of 1.2E X 10-7 torr. When I use source temp of 200C, it pass the leak test, it also pass the detector drift test. However, the system cannot pass the optimization with error message “mass calibration failed”. The tune calibration failed too. I replaced a new filament, it didn’t help. I tried to optimize the instrument many times in the past few months, it always failed at this stage. The detector voltage is around 1480V.
some of the error messages in the logfile stated "69.160 is out of tolerance, expected mass 68.995", 262.82 is out of tolerance, expected 263.99".
DAS test give message testing the high gain ADC, ADC bit test:expected 59 or 60 but read 61 at DAC 8500, expected 108 or 109 but read 110 at DAC6345. test low gain, the system freeze.

Appreciate any advice you can share.

Michael

[Don_Hilton]

It depends on which version of ChromaTOF you are running as to the best way to handle this. Give LECO Service a call - I have found them to be helpful folks. The number I have for the US is 1-888-LECO-911 (1-888-532-6911).

I'ts been a while since I had to work with this, so I don't remember the details.

[mcqian]

I have Version 3.32 from 2007. I have sent LECO an email asking for help but haven't got any response yet. Maybe I should call them directly. I just hope it is not something major broken.

[Don_Hilton]

Probably nothing broken. From what I remember, if the detector voltage is a bit too high, the tops of the peaks (for the masses) flatten off a bit and toe software has a bit of trouble. The trick is to get the detector voltage back down and do the mass calibration.

ChromaTOF has seen some nice improvments - and I think there was one after yours that had some nice inprovements in peak detection and integration. Check with LECO on what it wouldtake to be sure you are up to date. They will probably suggest ChromaTOF 4 - and it does have some nice steps forward (that's what I'm running). (THe step from ChromaTOF 3 to 4 does cost.)

Also, the Pegaus does not drive like other mass specs - OK none of them drive like the others. And a TOF has some distinct features. So be sure you have someone who knows the instrument show you how to get the most out of it. And LECO has a class for users in St. Joseph Michigan.

Let us know how it goes.