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- Posts: 12
- Joined: Fri Nov 04, 2022 9:21 pm
- Location: Canada
I am having some retention time issues where the peak may shift from 4.937min to 5.478min for one example (this is enough of a shift that chemstation cannot identify it as the same compound)
I am 100% confident this is the same analyte because the runs are just repeats of the same vial.
I am using full reports so I can see that the initial and final column temp is the exact same, flow is the exact same, pressure changes by at most 0.3bar.
Some background info:
- Using an isocratic eluent 75% Acetonitrile 25% water both are obviously HPLC Grade
- Sample is 95% solvent matched (950uL 25/75 H2O/ACN + 50uL Methanol)
- Column is basically brand new minus calibration runs and a handful of samples
- All the peek tubing in the HPLC is new
- The HPLC is an Agilent 1100: Units: G1322A, G1311A, G1315A, G1316A, G1329A, G1330A
- Flow rate: 0.700mL/min
- Average pressure: 173bar
- Column temp: 35C
- Injector: 10uL
- DAD: 225,4 Ref 370,80, range 190-700, step 0.5, slit 4, response 0.1s.
- Agilent Chemstation Rev. B.04.03-SP1 [87]
- Analyzing cannabinoids for potency 0-500ng/uL = 0-100%
- Problem seems to persist independent of analyte concentration (ie. a 5% control will be just as inconsistent with respect to retention time as a 100% control)
What could be causing this kind of shift in retention time?