title: Using contemporary liquid chromatography theory and technology to improve capillary gradient ion-exchange separations.
abstract: The gradient-performance limits of capillary ion chromatography have been assessed at maximum system pressure (34.5 MPa) using capillary columns packed with 4.1 μm macroporous anion-exchange particles coated with 65 nm positively-charged nanobeads. In analogy to the van-Deemter curve, the gradient performance was assessed applying different flow rates, while decreasing the gradient time inversely proportional to the increase in flow rate in order to maintain the same retention properties. The gradient kinetic-performance limits were determined at maximum system pressure, applying tG/t0=5, 10, and 20. In addition, the effect of retention on peak width was assessed in gradient mode for mono-, di-, and trivalent inorganic anions. The peak width of late-eluting ions can be significantly reduced by using concave gradient, resulting in better detection sensitivity. A signal enhancement factor of 8 was measured for a late-eluting ion when applying a concave instead of a linear gradient. For the analysis of a complex anion mixture, a coupled column with a total length of 1.05 m was operated at the kinetic-performance limit applying a linear 250 min gradient (tG/t0=10). The peak capacity varied between 200 and 380 depending on analyte retention, and hence on charge and size of the ion.
authors.affiliation: Vrije Universiteit Brussel, Department of Chemical Engineering, Pleinlaan 2, B-1050 Brussels, Belgium.
authors.forename: Bert
authors.initials: B
authors.lastname: Wouters
authors.affiliation: Vrije Universiteit Brussel, Department of Chemical Engineering, Pleinlaan 2, B-1050 Brussels, Belgium.
authors.forename: Ken
authors.initials: K
authors.lastname: Broeckhoven
authors.affiliation: Vrije Universiteit Brussel, Department of Chemical Engineering, Pleinlaan 2, B-1050 Brussels, Belgium.
authors.forename: Sam
authors.initials: S
authors.lastname: Wouters
authors.affiliation: Thermo Fisher Scientific, Takkebijsters 1, 4817 BL Breda, The Netherlands.
authors.forename: Cees
authors.initials: C
authors.lastname: Bruggink
authors.affiliation: Thermo Fisher Scientific, 501 Mercury Drive, Sunnyvale, CA, USA.
authors.forename: Yury
authors.initials: Y
authors.lastname: Agroskin
authors.affiliation: Thermo Fisher Scientific, 501 Mercury Drive, Sunnyvale, CA, USA.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Pohl
authors.affiliation: Vrije Universiteit Brussel, Department of Chemical Engineering, Pleinlaan 2, B-1050 Brussels, Belgium. Electronic address: seeltink@vub.ac.be.
authors.forename: Sebastiaan
authors.initials: S
authors.lastname: Eeltink
mesh_terms: D000838:Anions / Q000737:chemistry; D002852:Chromatography, Ion Exchange / Q000295:instrumentation / Q000379:methods*; D007700:Kinetics; D057230:Limit of Detection; D011312:Pressure
chemical_list: D000838:Anions
keywords: Column coupling; Detection limit; Gradient LC; Kinetic plot; Method development