Discussion Category:  GC-Ion Trap

Mass Readings slightly off

The mass readings for my Saturn 2000 is slightly off.  PFTBA peak at 132 reads 131.8  or the peak at 69 reads 68.8.   Primary peak for Naphthalene (128) reads 128.1    Is this normal?

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Vernon Pate
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Dan Ste.MarieReply by
Dan Ste.Marie

Vernon,

For this MS the accuracy of the mass should be within about 0.1 amu of the true value.  This are slightly off.  When was the last time the MS was cleaned and tuned?

Dan


Dan Ste.Marie

RJ2 Instrument Services

Erie, PA

www.rj2.biz

   
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Vernon Pate

Cleaned last week.  I Autotune everyday that I use the instrument.

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Dan Ste.MarieReply by
Dan Ste.Marie

Vernon,

I would run a full diagnostics to ensure theere are no reported errors and then I would check the Rf adjustment as well as the axial modulation (check in the manual for procedures if you have not done this before)

Dan


Dan Ste.Marie

RJ2 Instrument Services

Erie, PA

www.rj2.biz

   
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Vernon Pate

1. Passed Full Diagnostics

2. RF tuning Results:

 Average: 432

HIghest: 953

 

Axial Modulation at 4.0

Not sure how to tell if lowering the Axial Modulation will improve the mass accuracy.

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Dan Ste.MarieReply by
Dan Ste.Marie

Vernon,

I would suggest testing the mass accuracy when setting the modulation at 3.0 and 5.0 to see if there is an appreciable difference in mass assignment.  Make sure to look at several of the tuning ions and not just one ion as the magnitude of the mass can be a factor with this setting.

Dan


Dan Ste.Marie

RJ2 Instrument Services

Erie, PA

www.rj2.biz

   
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Vernon Pate

Lowered the Axial Modulation did the trick.

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Dan Ste.MarieReply by
Dan Ste.Marie

Very good


Dan Ste.Marie

RJ2 Instrument Services

Erie, PA

www.rj2.biz

   
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