We are experiencing a very strange issue (very broad peak) with Dimethyl Formamide Solvent when run with one particular residual solvent method utilizing Dimethyl Formamide as Diluent.
Method has been run for the past 4/5 years without any issues. Last month it was noticed that DMF diluent peak width has increased by a factor of 10 i.e. from 0.3min to 3min+ shark fin shaped.
Area is identical to that obtained in the past years and repeatable.
Sequences run on different GC systems with identical setup and also column replaced with new one twice, without any improvement.
GC systems have been checked but no issues found. Systems serviced and qualified on an annual basis; (one of them less than 1 month)
Any other methods run on systems work fine without any observable discrepancies.
GC Method parameters:
Equipment: 7890B GC + 7697A HSS
Column: DB-WAX 30m x 0.53mm x 1.0um; Helium Constant Flow @ 3ml/min
Inlet: SSI; 150 degC; Split 1:10; Septum purge 3ml/min
Detector: FID; 200 degC; 40ml/min Fuel; 400ml/min Oxidizer; 30ml/min Makeup (N2)
Oven: 35 deg for 6 min; 15deg/min up to 200 deg hold 3 minutes.
HSS Method parameters:
Incubation Temperature: 80degC
Loop Temperature: 90degC
Transfer Line Temperature: 100degC
Incubation time: 30 minutes
All other parameters: As per default method
Has anybody ever encountered such an issue?
Can anyone help?