BFB continually failing 75/95 ratio.

[Ziggy80]

Greetings!

I am currently having a problem passing a BFB tune for method TO-15(Air analysis method). My setup is a 5973 with a refuribished metal quad analyzer that has been in the instrument for a little over a year(The instrument as a whole is about 8 years old).

The problem is the mass 75/95 ratio, 75 is consistently high, typically around 70-80% or higher. I have taken serveral steps to troubleshoot the problem; new repeller, new multiplier, multiple source cleanings(the thing is sparkling now). I have utilized the Atune and BFB tune functions and manually adjusted settings, but no dice, mass 75 will not cooperate. I have even re-installed my chemstation software to rule out file corruption. I am currently waiting for new source parts to arrive and will be replacing those in the next few days.

Has anyone run into this type of problem or have any advice for lowering mass 75? I feel like it is some sort of hardware issue, but so far I have not been able to pin anything down.

This is my first post to the forums, so if there is any info I am missing or anything else that would be helpful, please let me know.

Thank you very much!

[bisnettrj2]

You probably have already seen this document, but if not, maybe it will help:

http://www.chem.agilent.com/Library/app ... 4373EN.pdf

[Yama001]

We have a 5975C that behaves like that. We manage it by tweaking the Target tune to produce a PFTBA spectrum with 131 and 219 at 50 to 60 percent, with 131 a bit higher than 219. Every source is a bit unique, though.

[James_Ball]

As above every source is different and you will get different values for every passing tune.

Do you have the Entrance Lens Offset running in Variable mode or Fixed mode?

In the Variable mode you can edit it to different values of Entrance Lens Offset at different masses.

When you are in the manual tuning Parameters window, look under More Parameters and on the list will by Dynamic Ramping. Open that and choose Entrance Lens Offset(should be the default). Here you can manually alter the different values for the parameter at different masses. Since 75 is too high compared to 95, try adjusting the mass 69 and mass 100 values. To find out how you may need to change them, uncheck the box at the top to enable/disable dynamic ramping then do a ramp of Entrance Lens Offset at mass 69, 100, 131 and record where the ramps maximize. Then reload the tune values and go back in and adjust as needed, moving 100 closer to the maximum if it isnt already there and 69 away from the maximum.

You may want to find the maximum for mass 50 while you are ramping just in case you begin to lose it while adjusting for mass 75.

I normally have to use this to tweak mass 50 because the response is too low on my instruments but I have had one before that gave the same problem with 75 being too high. The lighter masses are more difficult to tweak with just the normal lens settings because they are so close to each other and moving the lenses tends to affect them all the same.