Delta psi doubt

[Davidantony]

Dear All,
I have working in a waters 2695 HPLC conected to MSMS.I have doubt on delta psi.Is there any relation in RT of compounds.Our Application Specialist tell us it should below 50 before taking next injection.What is delta PSI.Whether it is the difference between minimum and maximum pressure.One more doubt is what is system and sample pressure

[lmh]

Might be wrong, but I think the delta psi is the pressure ripple during pumping. If it is large (i.e. pressure is fluctuating up and down) that usually means that there is an air-bubble in the pump somewhere, and the pump needs priming. An air bubble would cause the flow to be less than what you expect, and very erratic. Hence your Application Specialist not wanting to proceed unless delta psi is small.

System pressure is the pressure in the pump. Too high means that something in the conventional flow-path from pump to detector is blocked.

Sample pressure is the pressure in the autosampler part of the instrument (sample manager), I think it's measured somewhere between the syringe and the loop. Too high means that the loop, needle, or some other part of Waters' phenomenally complicated injection system is blocked. Too low means something in the autosampler has sprung a leak, or the whole system is full of air (as happens if you make injections from vials that don't contain enough liquid...)