Chromatography Forum

Hi,

I have a question that is more for my interest than an inherent problem per se (I hope). I run a Agilent 1200 binary pump for reverse phase (isocratic mobile phase) with an ECD. I always see a wavy baseline (quick small sin wave - I assume pump noise as ECD's are quite sensitive to flow rate). In trying to minimise this I have optimised the 'compressibility' and 'stroke volume' settings.

I figured that using both pumps (if they were pumping out of sync) would be beneficial and should increase the frequency but decrease the magnitude of this wave (does that make sense?). A lower magnitude would give me a better Signal:noise so this is what I am aiming for. However, no matter what % each pump is at or what stroke volume (these can be individually assigned) using both increases the magnitude of this noise. I was wondering if anyone could explain to me why this occurs. It may be a silly question but I just don't 'get it'.

Thanks for your help.

Hi

Is it a 1200SL pump, if so is damper attached? Usually the sin wave you get is caused by either a valve failing or mixing issues ( typical seen with solvents with vastly varying absorbances ). I would run the leak / pressure test and see what you get. Typically 1100 / 1200 binarys have the pump A inlet valve cartridge fail.

Hope this helps