Question from jumn*** Why ESI mode doesn't Work for Flavonoids?
According my Tech lab Notebook(#2006-09), my answer to your question is: 100% Negative ESI Mode should be Good for Flavonoids.
According my Tech lab Notebook(#2006-09), my answer to your question is: 100% Negative ESI Mode should be Good for Flavonoids.Your analyte is belong to Flavonoid family. {Molecular structure of the flavone backbone (2-phenyl-1,4-benzopyrone)}. It contains lot of Phenols, so technically it should be good under Negative ESI mode.
(1) Try to use H2O-MeOH as mobile phase, the Injection Conc. is 1ug/ml.
If above method doesn't work,
(2) Method Development: under Negative ESI mode, direct injection sample through syringe pump. (Use syringe pump, easy tuning & time saving, but need to pay attention on the cleaning of capillary after tuning or could try the six-valve direct injection if feel confident, could obtain a good baseline with min background, time costing:> )
Add some Ammonia to enhance the ion compounds or 5mM of ammonium acetate should be fine. Optimize spray-voltage, voltage plate, capillary voltage/Temp, shealth gas, aux gas, flow rate.
The starting analyte Injection Conc. is from 1 ppm.
If you still have any problem, highly recommend you talk to your BOSS: Double check that is the right "Flavonoid" or the purity of Flavonoid.
Try to use LC to testify your suspect,
Column:2.1 X 50 mm, 5 µm , 100 Å , C18
Temp: 40℃
Mobile: A (H2O) with B (MeOH) 30-70% gradient elute in 5 min.
Flow rate: 1 ml/min.
Wavelength: 340 nm.
if there are multi-peaks in the chromatograms, then maybe explain the problems in NegESI mode. Always talk to your manager first, Don't let him to be the last ONE surprised.
Please update me if have something new, thanks.
Reference Paper: JOURNAL OF MASS SPECTROMETRY, 2004; 39: 312–321: LC-DAD-ESI Tandem MassSpect.
