How to set Dual AJS ESI and TOF Parameters for non-target measurements?

LC-TOFMS dual-ajs-esi 6230B 

I am looking forward to analyze water samples using LC-TOFMS in non-targeted manner. I am using Agilent 6230B LC-TOFMS system with Dual AJS ESI. (TOF Firmware: 17.723, LC/MS Data Acquisition Version B.09.00 Build 9.0.9044.0)

 

In method editor there are many parameters in Source, Acquisition and Ref Mass tab, where I do not know how to choose the most suitable value. In help file there is some information what these parameters mean but still having hard time to choose the values. Is there a documentation which explains the parameters and how to set the values? There are some screenshots where you can see the parameters. My flow rate will be between 0.200 - 0.300 mL/min.

 

Thank you for your help in advance

attachments.zip
Parents
  • Dear Dawn,

    Thank you very much for your fast response and detailed explanation.

    For me there are some unclear points remaining.

    1) In Ref Mass tab: Does the detection window parameter influence much.

    2) If I understand correctly a nozzle voltage helps creating droplets. So a value of 0 should be very bad. I will set it 1000 but is there a easy logic how to choose this value?

     

    Kind regards

  • You're very welcome. 

     

    To answer your remaining questions . . .

    1.  The detection window of 100ppm and 1000 counts means the instrument has to see each reference ion within 100 ppm of it's theoretical exact mass and at least 1000 counts.  If you can't detect the reference ions within 100 ppm- it could be that the TOF was not calibrated recently enough (this should be performed every day you intend to run samples on the TOF) or in some cases it could be that it is picking up a small background interference which can occasionally happen for purine.  If you don't have at least 1000 counts of reference ion, you should first check that reference solution is coming out of the reference nebulizer (about 1 drop every 8-10 seconds) and if it is following ok then you can consider increasing the concentration of those reference ions in bottle A.  You should not be in the habit of increasing the 100ppm or decreasing the 1000 counts in order to detect reference as you could be referencing off the wrong ion. 

     

    2.  Before the jet stream, the nebulizer could be easily seen when you opened the source however now it is enclosed in that "nozzle."  Nozzle voltage can be thought of as an extraction voltage and is compound dependent.  A value of zero is ok to use and you will see many references where the nozzle is set anywhere from 0 up to 2000.  I typically will choose 1000V when I don't know specifically where to set it because there could be many compounds of interest (not all in the same class of compounds either) in my sample just as is your situation.  If you get into a situation where you have a class of compounds or one specific compound that you need to optimize the source towards to get the best sensitivity, this is where you would optimize this nozzle voltage (typically will be done from 0 to 2000V in increments of 500V).  

Reply
  • You're very welcome. 

     

    To answer your remaining questions . . .

    1.  The detection window of 100ppm and 1000 counts means the instrument has to see each reference ion within 100 ppm of it's theoretical exact mass and at least 1000 counts.  If you can't detect the reference ions within 100 ppm- it could be that the TOF was not calibrated recently enough (this should be performed every day you intend to run samples on the TOF) or in some cases it could be that it is picking up a small background interference which can occasionally happen for purine.  If you don't have at least 1000 counts of reference ion, you should first check that reference solution is coming out of the reference nebulizer (about 1 drop every 8-10 seconds) and if it is following ok then you can consider increasing the concentration of those reference ions in bottle A.  You should not be in the habit of increasing the 100ppm or decreasing the 1000 counts in order to detect reference as you could be referencing off the wrong ion. 

     

    2.  Before the jet stream, the nebulizer could be easily seen when you opened the source however now it is enclosed in that "nozzle."  Nozzle voltage can be thought of as an extraction voltage and is compound dependent.  A value of zero is ok to use and you will see many references where the nozzle is set anywhere from 0 up to 2000.  I typically will choose 1000V when I don't know specifically where to set it because there could be many compounds of interest (not all in the same class of compounds either) in my sample just as is your situation.  If you get into a situation where you have a class of compounds or one specific compound that you need to optimize the source towards to get the best sensitivity, this is where you would optimize this nozzle voltage (typically will be done from 0 to 2000V in increments of 500V).  

Children
No Data
Was this helpful?