title: Comparison of peak shape in hydrophilic interaction chromatography using acidic salt buffers and simple acid solutions.
abstract: The retention and peak shape of neutral, basic and acidic solutes was studied on hydrophilic interaction chromatography (HILIC) stationary phases that showed both strong and weak ionic retention characteristics, using aqueous-acetonitrile mobile phases containing either formic acid (FA), ammonium formate (AF) or phosphoric acid (PA). The effect of organic solvent concentration on the results was also studied. Peak shape was good for neutrals under most mobile phase conditions. However, peak shapes for ionised solutes, particularly for basic compounds, were considerably worse in FA than AF. Even neutral compounds showed deterioration in performance with FA when the mobile phase water concentration was reduced. The poor performance in FA cannot be entirely attributed to the negative impact of ionic retention on ionised silanols on the underlying silica base materials, as results using PA at lower pH (where their ionisation is suppressed) were inferior to those in AF. Besides the moderating influence of the salt cation on ionic retention, it is likely that salt buffers improve peak shape due to the increased ionic strength of the mobile phase and its impact on the formation of the water layer on the column surface.
authors.affiliation: Centre for Research in Biosciences, University of the West of England, Frenchay, Bristol BS16 1QY, UK.
authors.forename: James C
authors.initials: JC
authors.lastname: Heaton
authors.affiliation: Centre for Research in Biosciences, University of the West of England, Frenchay, Bristol BS16 1QY, UK.
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Russell
authors.affiliation: Analytical Chemistry, GlaxoSmithKline, Gunnels Wood Road, Stevenage, UK.
authors.forename: Tim
authors.initials: T
authors.lastname: Underwood
authors.affiliation: Analytical Chemistry, GlaxoSmithKline, Gunnels Wood Road, Stevenage, UK.
authors.forename: Robert
authors.initials: R
authors.lastname: Boughtflower
authors.affiliation: Centre for Research in Biosciences, University of the West of England, Frenchay, Bristol BS16 1QY, UK. Electronic address: david.mccalley@uwe.ac.uk.
authors.forename: David V
authors.initials: DV
authors.lastname: McCalley
mesh_terms: D000097:Acetonitriles; D002021:Buffers; D002853:Chromatography, Liquid / Q000379:methods*; D005561:Formates; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D009994:Osmolar Concentration; D010756:Phosphoric Acids; D012822:Silicon Dioxide; D012996:Solutions; D014867:Water
chemical_list: D000097:Acetonitriles; D002021:Buffers; D005561:Formates; D010756:Phosphoric Acids; D012996:Solutions; D014867:Water; C030544:formic acid; D012822:Silicon Dioxide; C030242:phosphoric acid; C032159:acetonitrile
keywords: Buffers; Column efficiency; HILIC; Hydride phases