Polymer-Based Mixed-Mode Columns

Polymer-based mixed-mode columns are commercialized under the trade name Thermo Scientific Dionex OmniPac (Thermo Fisher Scientific, Waltham, MA, USA). They allow separations based on ion-exchange, ion-pair, reversed-phase, and ion-suppression interactions, depending on the type of eluent. Any combinations of these interactions, at the same time or in succession, can also be employed to separate analyte species. 

8 ion suppression separator coiumn chemically bonded silica (ODS) eiuent 20mmoi/L H3PO4-i-20mmol/L HOAc/MeCN gradient linear, 5% MeCN to 30% in 20 min (b) mixedmode separator column OmnIPac PAX-500 eluent KOH/KCl/MeCN (80 20 v/v) gradient linear, 0.5 mmol/L KOH + 50 mmol/L KCI to 

4mmol/L KOH-1-400 mmol/L KCI in 20 min flow rates 1 mlVmin detection UV(254nm) peaks (1) benzoate, (2) 1,2-benzenedicarboxy-late, (3) 1,4-benzenedicarboxylate, (4) 1,3-ben-zenedicarboxylate, (5) 1,2,3-benzenetricar-boxylate, (6) 1,2,4-benzenetricarboxylate, 

9 v/v) to 20mmol/L Na2C03/MeCN (80 20 v/v) in lOmin flow rate 1 mL/min detection UV (254 nm) injection volume 20 pL peaks  

Among organic cations, OmniPac PCX-100 is predominantly used for analyzing biogenic amines such as catecholamines, choline, and acetylcholine. In comparison to separations on ODS phases, OmniPac separations are characterized by a different selectivity. Choline and acetylcholine, for 

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