Waters HPLC Diagnóstico Y Corrección De Anomalías página 114

Problem – – Sample Draw Volume Problem
Reproducibility - - Reproducibility
Symptom: Peak area increases after first injection from the same vial (first injection –
low, latter injections OK)
— Possible cause:
FIRST Time. "Vacuum formation"
injection needle.
— Vacuum draws some sample back out of the needle
Situation can be aggravated by over filling the vial Situation can be aggravated by over filling the vial
o o
(Never fill the vial all the way to the top)
— Test: Remove cap and septum* from the vial.Perform multiple injections. Measure
peak area to determine if the septum/cap is the
•*
Some auto samplers may have to have the vial sensor disabled
•Vial A
•Inj. 1
•Area = 200,000
Sample Draw Volume
Venting Venting
Inadequate venting upon needle piercing the septum/cap for the
caused by the septum/cap sealing around the
cause.
•Vial A
•Inj.2
•Area = 250,000
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