title: Improving peak shapes with counter gradients in two-dimensional high performance liquid chromatography.
abstract: To achieve the greatest peak capacity in two-dimensional high performance liquid chromatography (2D-HPLC) a gradient should be operated in both separation dimensions. However, it is known that when an injection solvent that is stronger than the initial mobile phase composition is deleterious to peak performance, thus causing problems when cutting a portion from one gradient into another. This was overcome when coupling hydrophilic interaction with reversed phase chromatography by introducing a counter gradient that changed the solvent strength of the second dimension injection. It was found that an injection solvent composition of 20% acetonitrile in water gave acceptable results in one-dimensional simulations with an initial composition of 5% acetonitrile. When this was transferred to a 2D-HPLC separation of standards it was found that a marked improvement in peak shape was gained for the moderately retained analytes (phenol and dimethyl phthalate), some improvement for the weakly retained caffeine and very little change for the strongly retained n-propylbenzene and anthracene which already displayed good chromatographic profiles. This effect was transferred when applied to a 2D-HPLC separation of a coffee extract where the indecipherable retention profile was transformed to a successful application multidimensional chromatography with peaks occupying 71% of the separation space according to the geometric approach to factor analysis.
authors.affiliation: Centre for Chemistry and Biotechnology, Faculty of Science, Engineering and Built Environment, Deakin University, Geelong, Vic. 3216, Australia. Electronic address: paul.stevenson@deakin.edu.au.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Stevenson
authors.affiliation: Centre for Chemistry and Biotechnology, Faculty of Science, Engineering and Built Environment, Deakin University, Geelong, Vic. 3216, Australia.
authors.forename: Danielle N
authors.initials: DN
authors.lastname: Bassanese
authors.affiliation: Centre for Chemistry and Biotechnology, Faculty of Science, Engineering and Built Environment, Deakin University, Geelong, Vic. 3216, Australia.
authors.forename: Xavier A
authors.initials: XA
authors.lastname: Conlan
authors.affiliation: Centre for Chemistry and Biotechnology, Faculty of Science, Engineering and Built Environment, Deakin University, Geelong, Vic. 3216, Australia.
authors.forename: Neil W
authors.initials: NW
authors.lastname: Barnett
mesh_terms: D000097:Acetonitriles; D000873:Anthracenes / Q000737:chemistry; D001555:Benzene Derivatives / Q000737:chemistry; D002110:Caffeine / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D056148:Chromatography, Reverse-Phase / Q000379:methods*; D003069:Coffee / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D019800:Phenol / Q000737:chemistry; D010795:Phthalic Acids / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry; D012997:Solvents; D013890:Thiourea / Q000737:chemistry; D014867:Water
chemical_list: D000097:Acetonitriles; D000873:Anthracenes; D001555:Benzene Derivatives; D003069:Coffee; D010795:Phthalic Acids; D010936:Plant Extracts; D012997:Solvents; D014867:Water; C024629:dimethyl phthalate; C024268:n-propylbenzene; D019800:Phenol; D002110:Caffeine; C034020:anthracene; D013890:Thiourea; C032159:acetonitrile
keywords: Column efficiency; Counter gradient; Natural product separations; Solvent strength; Two-dimensional high performance liquid chromatography