7010/8890 HES System - MS1 Abundances low (6-8 million) - poor isotope peak resolution / peak shape in tune - lowering sensitivity

Hello GCMSTQ Friends!

My lab had purchased a 8890/7010 system with HES source (via 3rd party) a few months ago for low level pesticide analysis in cannabis. Previously we have been working with a 7890/7000C with Xtr EI Source for the last few years. Every since we have begun using the 7010 with HES, I have felt there is some issue with MS1 ion abundances, in turn lowering overall sensitivity depending on the tune applied. I am used to 6-10 million counts for PTBFA 69 in my tunes on the 7000C, but was expecting at least double that with the HES. 

Peak shape of tune ions in MS1 are a bit off shaped, and isotope "foot" resolution is not baseline resolved as it appears to be in MS2 (also relative abundances seem low, particularly in mid and high masses). I have opened profile screening in manual tune to live monitor both MS1 and MS2, and am seeing about 1/3 ion abundances in MS1 as MS2. Is this normal? Should both profile abundances be equal? I have attached 2 versions of tune files, one month apart. I have tried tuning from default a number of times with minimal improvements. In addition, we do have hydrogen jetclean installed on this instrument, so I am pretty sure its not a dirty source.

Could MS1 quads be dirty causing this issue?

I would greatly appreciate any and all feedback, Thanks!

  • What is the serial number on that MS?  Please share a picture of the serial number label....The one listed on the tune report is invalid.

    How many runs on the system?      8890 and Intuvo: Service Mode, Instrument, Usage

    The Tune PFTBA counts do not have anything to do with the ion source type. The tune algorithm has targets to achieve and as long as 69 is big enough, it is acceptable. The tune EMV is fabulous at 989V and the max gain is good at 42052.  What version of MassHunter Acquisition is installed? 

    MS1 abundances are less than MS2 abundances for a couple of reasons but yes, that's normal.

    JetClean only cleans the parts of the ion source that have hydrogen and electrons on them at the same time, so it does not clean PE1, PE2, Ion Focus, and Entrance lens. It does not clean the extractor lens insulator nor the transferline tip seal both of which should be replaced quite frequently.  Clean the source. Replace the filament, extractor lens insulator, lens stack insulator, and tip seal.  Make sure that the column is not installed too far out of the transferline - I like flush with the end of the tipseal ceramic. When the system is vented and the analyzer door is open to remove the source, take pictures of the source parts disassembled, a picture down inside the source radiator of the quad end cap ceramic, and of the front of the collision cell and share those photos, too.

    The tune at 300° C ion source temperature will have lower 219 and 502 relative abundances than with the temperature at 230° C.  That's not a bad thing on a QQQ system and the HES seems to do very well at 300° C.

    The default collision cell gas flows for a 7010x are 4.0 ml/min of quench helium and 1.5 ml/min of collision nitrogen. 2.25/1.5 are the 7000x defaults. The additional helium metastables created in the HES can cause higher detector noise and the additional quench flow reduces that.

    Column flow 1.4 into the HES is the maximum that I would ever recommend. Higher flows change the spectral tilt on the HES quicker than on the orthogonal source.   

    The Q1 DIP value at 1000 is 66.3% which is a first indication that the quad is probably OK - - but that does not tell you if it's dirty necessarily. 

    Fix the air leak.  8.13% nitrogen and 2.18% oxygen is not great. It could be that the high helium carrier gas flow is making this artificially high, so first:  Try reducing the temp to 230, column one flow to 1.05 ml/min and column 2 flow to 1.2, CC gases to 4.0/1.5, and tune again then share that report.

    To recap. Fix the leak. Clean the source. Replace the consumables. Take pictures.

  • Paul, Thanks so much for your detailed reply.

    I have attached pictures of the MS serial sticker, and front enclosure. Unfortunately, the 8890 we have was not originally paired with this MS (it was brand new, the MS was not) so it is hard to know how many runs it has seen. Masshunter Acquisition Version 10.0 Service Release 1, Build 10.0.384.1 is what is currently installed. 

    Within the past 3 months we have replaced the filament, extractor lens insulator, & lens stack insulator. We have not yet replaced the tip seal, and will have one ordered this week to replace it when we clean the source. I was not able to vent last week due to samples, but will follow suit with pictures of everything once I do. 

    Regarding the collision gas/quench flow rates, the software does seem to default to the 2.25/1.5 settings (I was unaware/nearly every Agilent application note that  I have regarding pesticide methods reference the lower flow settings, even when stating 7010x series). Is there detriment in terms of reproducibility in running the lower flow? Should I switch immediately to the 4.0/1.5?

    I have also attached two tune files with the air leak resolved,  one with the column flow settings, temps, and CC gases adjusted as your requested. MS1 looks about the same to me. Thanks again for your help!

     

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