e2695 and injection repeatability problem

[Kasiban]

Dear All,

When try to inject standard in same vial in 5 duplicate with Alliance e2695, we 've got %RSD of Area > 2.0% in every test method.

Anyone can help, what is wrong with my instrument?

Best regards,
Kasiban

[Bull76]

Hi,

Have you purged the Injector and verified that there is no bubble in the syringe. Also have you done a compressiblity test?

Regards,
Bull76

[Kasiban]

Hi Bull76,

I did it both purge injector and compessibility check.
No sign of problem from air bubble.
System pressure is constant before inject, equilibrate time is good (more than 20times of column volume), but we still get repeatability problem!

Regards,
Kasiban

[AA]

Try using pre-slit septa, they can often help.

[Kasiban]

Hi AA,

I am using pre-slit vial.


Regards,
Kasiban

[Bull76]

Hi,

If the compressibility test passed. Then you need to check the syringe or even replace the syringe. Possibly need to check V2 for leakage or buffer build up.

Regards,
Bull76.

[tom jupille]

Also take a look at your injection volume vs. the volume of the installed. Laminar flow effects can affect precision when you get up above 50% or so of the loop volume.

[unmgvar]

does the 5 replicates give a behavior of areas
going down
going up
"all over the place"
only the first one is too low
the last one is too low

i remember also a case that a non-centered needle in a alliance system, caused a rep problem.

[ym3142]

what is the concentration?

What is the peak area or S/N?

How long the method runs?

what is the diluent? 100% aqueous or 100% ACN?

How is your blank baseline? DO you see any interference? How is you peak integrate?

what is your injection volume? 1 uL or 200 uL?

What is loop size? 20 uL or 2000 uL?

Thanks for sharing

[WillyOne]

Not too much data to send an opinion...
Anyway check the inner diameter of the loop. I've suffered a lot using a 100 microliters very short but very wide.
Seems that eluent at certain flow values can't sweep up completely the analyte off the loop.
Perhaps you can try to change the loop for a narrower one.
Please excuse my english

[Renato]

Have you tried to change the Seal Pack and Needle?
V3 valve could be the defective part too.
Renato