injector repeatabiltiy

[moonchips]

I would like to have a question about HPLC injector.

in our system suitability, we inject 5 injections of assay standard and then 2 injections of check standard.

We have 4 of the injections of assay standard with peak area about 3650, and the fifth one dropped to 3500. the RSD% was about 1.8%. It still passed, but ususally it is smaller than 0.5%. What could went wrong?

Thanks a lot

[danko]

Not enough standard solution in the vial for the fifth injection? Yes/no/maybe?

Best Regards

[anirbanrc]

Check whether the septa of the vial is OK.Sometimes if it fragements , or goes into vial , you get some descrepancy or reason given by Danko, insufficient qty in the vial