Bad reproducility

[afzal81]

Dear all

I am having irreproducible area with the manual injector while injecting sample, but this is not the issue with the standard. I have the following system.
Knauer s 1000 pump, s 2500 uv detector and manual injector
I have changed the rotor seal of the injector, it didn't work. Somebody please give me suggestion.

afzal123_ahmed@yahoo.com

[Gerhard Kratz]

Maybe your sample has different viscosity than your standard. What volume has your sample loop? Is the stainless steel part of your injector smooth? Do you see any leaks? Do you load the sample loop with a fixed volume or do you over fill the loop?

[remesquaddie]

Non reproducibility on any HPLC system can be attributed to several different factors.
1: Air in your syringe, 2; Leaks at the injector port, 3:worn rotor.
Check all of the above.
Good luck.

[skunked_once]

Be sure that you are using the proper procedure for manual injections. If you are using the sample loop to set your injection volume, you should load 2-3X the loop volume to get a consistent loop fill. If you are measuring the volume by the syringe, it should be less than half of the volume of the sample loop.