Precision of 2~3 uL injection on 2695e

Hi, since there is no section for 2695, I have to post it here.

I have some problem with the precision of sub-5 uL injection on 2695. Two methods I received were developed/validated on Agilent 1100/1200, but injection precision on 2695 is challenging even with 25-uL syringe installed and configured in system:

==Method 1===
Sample diluent: 75% Ethanol/25% Water
Injection volume: 3 uL, slow speed draw
MP A: water/TFA
Gradient: 25 min, 90% A to 10%A
Column: 4.6x150 C18
Flow: 1 mL/min
Wavelength: 228
%RSD (n=6): 3.3, need < 2.0
Bracketing recovery: 95 to 105, randomly up and down
Carryover: no

==Method 2===
Sample diluent: 30% ACN/70% Water
Injection volume: 2 uL
MP A: water/H3PO4/TEA
Gradient: 3.1 min, 90% A to 10%A
Column: 4.6x50 C18
Flow: 1.5 mL/min
Carryover: no
%RSD (n=6): 5.6, need < 2.0
Bracketing recovery: randomly up and down
Carryover: no

LCs are serviced routinely by Waters engineer.

Does any one know how to improve low-volume injection precision on 2695?


  • Hi ronery,
    It sounds like you have already made all the hardware changes to give you the best result for low volume injections, so now it is just a matter of ensuring that the rest of the hardware is not adding error to your analysis.  Can I ask what volume you are trying to inject and what RSD you are getting today?