Chromatography Forum

Hello,

I have recently run a method that uses 100% MeOH as MP-A and 100% EtOH as MP-B. Apparently the 2695 does not like this mixture since there were 'bubble found on compression' notices popping up all over the place during the gradient ramp, as well as RT shifts and unacceptable recoveries. The same thing happened on a different 2695. I am led to believe that the problem is with the mixing of the 2 solvents. Delta psi is all over the place as well and diagnostic tests indicate failure with a C/D ratio of about 17 (should be < 1.. This problem showed up after these analyses using these 2 solvents. Each mobile phase was filtered and helium sparged and the instrument has an inline degasser. Any thoughts? Thanks

Chris T

Maybe a vacuum chamber broken, or your degasser pump stuck?

Did you try using only 100%A, and see if the C/D ratio is still too high?

Ace

Yes, while running at 100% A the CD ratio is high. The bubble warnings tend to go away while running isocratically at 100% A and at higher percentages of MP B.
Just odd that the same mobile phases doing are the same thing to 2 different LCs within a week.