Agilent 1100 Injection Repeatability

[phiswiz]

Hi all,

I have a flukey thing that happened a little while ago and have not found a cause.

I have an Agilent 1100 system with a good performance history. I inject assay samples in duplicate and have to meet a ratio spec. Normally this is never a problem but I had a run of 13 samples (dual component) and had 2 ratios go out for one component and 5 ratios go out on the other component with only 1 sample in common. We have ruled out vial misplacement (we inject out of separate vials) and our metrology department came up empty.

Any ideas as to the cause?

[AdrianF]

Did the retention times remain the same? If it was an injector problem both peaks would be affected identically.

Incidentally I think it is a waste of time doing duplicate injections with a reliable system like the 1100.

[DR]

Separate sample preps for ea. vial? If so, I'd look there if the 1100 precision & linearity check out OK.

[rnelson]

I've seen that exact problem on an 1100, and we determined the cause to be a poor needle to needle seat seal. We found that the needle had been re-installed and not inserted properly into the needle holder (there is a small channel on the needle holder where the needle should sit which ensures a nice vertical alignment). If the needle is not in this channel, it would be possible for it to move slightly during injections.