Chromatography Forum

Dear All,
Iam using 2695 hplc systems, iam getting RSD up to 8-10%, my system's pressure is stable, no air bubble in injector needle, can any one letme know the possible causes?
Regards
Shoaib

RSD variation in area counts, or in retention times????

If retention times are stable/consistent, sounds like injection issue.

If there are no obvious signs of air bubbles or leaks in the autosampler the first place I would look is the six port valve, the rotor may be baddly worn or damaged.

If your samples are fairly viscous, or if sample viscosity varies a bit over different methods, check the sample draw speed on the plunger. Are you doing partial-loop injections or full-loop, and if you're using partial-loop injections are you ensuring that the injection volume is less than one-half of the loop volume?

Also verify your needle wash functionality.

Hi

If you have checked all the above solutions, then it may be the seal pack and / or one of the valves ( V2 ). If you feel comfortable remove the right hand cover and take a look to see if anything has been leaking. The manual helps with overhaul of these parts.

Good Luck