The pressure of LC fluctuates

[shangyer]

I was running LC/MS. After injection, the pressure keep climbing. After 5 min maybe, the pressure started to fluctuate from between 100 and 60psi. Like climbed to 100 and back to 60psi and then climbed to 100 again with 1psi/s. The thing is when I wash the column which 100% ACN or water/ACN 50/50 , it is stable. And I did not find any leaking!

[DR]

Type of LC?
Flow (gradient) program?
Mobile Phase composition(s)?

[Consumer Products Guy]

Like the Dr. ordered, provide more information. But it sure sounds more like a HPLC issue, not the detector. Without that information, I'd say to degas solvents better, purge out all/any bubbles, disconnect detector, and run pressure check tests if the pressure still fluctuates. It could be pump problem or a mixing problem, must isolate the issue. To rule out mixing issue, put all solvent leads in one reservoir, purge out all dead volume, and see if problem goes away (that way same will be pumped no matter how the individuals are mixed).