Agilent Technologies 5975C TAD VL MSD Troubleshooting And Maintenance Manual page 190

6
Vacuum System
Diffusion pump fluid that is exposed to air at operating temperature will
break down and turn dark brown or black. This reaction is called cracking.
Cracked pump fluid gives two symptoms: higher manifold pressure and high
background with a large peak at m/z 446.
See also
•
• The troubleshooting sections of the MSD ChemStation online help.
190
"Maintaining the Vacuum System" on page 89.
5975 Series MSD Troubleshooting and Maintenance Manual