Effects of Eluent pH on HILIC Mode (VG-50 2D)

Various sweeteners were analyzed using LC/MS methods with a polymer-based HILIC column, VG-50 2D. Two different eluents were compared: (A) alkaline solvent and (B) neutral solvent. The octanol-water partition coefficient of the analytes (log P, an indicator of compound's polarity) and their retention times (t_R) were plotted for each eluent condition. Their chromatograms are also shown below. Under the alkaline condition, a correlation between log P and retention time was observed; the lower the log P (higher polarity) of the analyte, the stronger the retention. On the other hand, under the neutral condition, the retentions of aspartame and acesulfame K were remarkably stronger. It can be assumed that aspartame and acesulfame K existed as anions under the neutral state, and the ion exchange effects with the amino group of the packing material strengthened their elution.


Sample : 2 μL, 50 μg/mL each
Aspartame
Sucralose
Acesulfame K
Xylitol
Glucose
Maltose

Column       : Shodex HILICpak VG-50 2D (2.0 mm I.D. x 150 mm)
Eluent       : (A) CH3CN/0.5 % NH3 aq.=80/20
               (B) CH3CN/50 mM CH3COONH4 aq.=80/20
Flow rate    : 0.3 mL/min
Detector     : ESI-MS (SIM)
Column temp. : 40 °C