I perform some solvent analysis (BTEX) one time by week. Every time I do a calibration curve by slope chage from 50 to 250 for example. I thought it could be some pneumatic problem related to split ratio, since my peaks are visualy incresing or decreasing. but my retention time is constant.
I also work with HPLC and my slope in my calibration curves are much more constant, change about 2%.
I already tried to re-do the standards, it give me the same result.
I am using a Shimadzu 17A, column 30m x 0,25mm.
Thanks in advance
By Ron on Monday, June 21, 2004 - 06:39 am:
Did you open a new sealed vial of standard and try making standards from that vial. BTEX standard concentrations will change even sitting in a freezer over a period of a month if the standard is in a vial with a septum which has been pierced.