stable pressur .. how stable is stabe ....?

[tarzan]

dear all...
we keep discussing stable back pressure ..
but how stable is stable ...?
in our c18 column,300mm, 5 micron particle size, 93:7 water:ACN ..0.5ml flow rate we get aback pressure of 95bar and it fluctuates by +/- 1bar.
however at 1.0 flow rate .. we get 210bar with +/- 5bar .. is this fluctuation accepted ...?

with best wishes

[dblux_]

Start with checking your pump specification for appropriate pressure parameter.

[daniel_aut]

As per operational qualification at install date.Then, if you establish other limits in you performance qualification/system suitability, use those.

[James_Ball]

The first HPLC I used 20 years ago from Waters said in the manual if you had less than 200psi fluctuation you had acceptable results, that is +/- 7bar. On our new Agilent systems I usually get less than 1 bar fluctuation.

Pressure fluctuation will usually cause baseline instability, so I guess the pressure fluctuation you can get by with is what still produces acceptable baseline fluctuation.

Just remember the more stable the easier it is on the column packing.