In a determination of erbicide I use a standard that containing 10 erbicides
at concentration 0,1 mg/L and with injection of diverse volumes the curve is
obteined in a range 0,01-0,1 mg/L.
I have made the first calibration three days after the pump down of MS detector,
(Agilent 1100 MSD) with a good level of vacuum (about 7E-006 Torr).
However, in a time of 8-10 days, the response of any single erbicide continue to
raise and arrive at a response augmented of 5-10%.
There is a reason for this behavior?

Thanks in advance.