Chromatography Forum

Dears,
I am working on HPLC system with PDA detector. My field work is beverages (nonalcoholic drinks).

Question is:
Analysis of additives and vitamines in soft drinks were excellent on Column Varian C18 250mm x 4.6mm

Now I work on ChromSep HPLC column SS 250 x 4.6mm Incl. holder with ChromSep guard column ChromSpher 5 C18

Analysis (Na-benzoat, K-Sorbate, Citric acid, Absorbic acid) on this column are bad. Only coffeine analyse is OK.
Mobile phase: 80% KH2PO4 0.025M, pH4.5 + 20% ACN
Flow rate: 1.3ml/min
Wavelength: 235nm
Mode: Isocratic


Do you have any suggestions? Maybe different mobile phase or something else.
Do you have application notes for these kind of analysis on this type of column (without ion-par reagense)?

Thank you and best regards

The method is not very good. You are working with phosphate at pH 4.5, where it has no buffering capacity whatsoever. Adjust the mobile phase pH to either around 3 or around 7! You peaks will move around somewhat, but the tailing should go away.

Dear Perica
Yes,
Years ago there were a lot of beverage methods out there using unusual buffering - most of which would not give reproducible chromatography.
I think now there are many better methods available. You may have to have two methods - one for additives - one for vitamins.
I would stick to low pH work if you can.
I don't think its possible to have one method unless you have only one characterised sample to analyse.
Best Regards

If you have a method that works consistently on a particular column, why change?