What is delta psi?

Good day! 

Can I know what is delta psi?  It seems that the delta psi is increasing when I increase the flow rate of the mobile phase but when I remove the flow rate it goes back to normal. By the way I am a beginner in using Alliance HPLC. 

Big thanks. 

Best regards,



  • Delta psi is just the difference in the minimum vs maximum psi observed over the last minute.  It is expected to be a larger value at higher flow rates/overall pressure.  It's especially good for gauging if your system is equilibrated or if there's an issue with the pump's check valves.