title: On-line solid phase extraction-liquid chromatography, with emphasis on modern bioanalysis and miniaturized systems.
abstract: On-line solid phase extraction (SPE)-liquid chromatography (LC) allows for automated, sensitive, precise and selective bioanalysis. It is a common feature in miniaturized- or nano LC systems, which are well suited for applications requiring high sensitivity and/or treatment of limited samples (laser micro-dissection samples, rare cancer stem cells, etc.). Traditionally, particles with reversed phase (RP) functional groups are used for the columns in SPE-LC systems. There is however an expanding diversity in SPE-LC combinations applied to meet today's bioanalytical challenges. Current online SPE-LC combinations employ, e.g. porous graphitic carbon (PGC) and hydrophilic interaction liquid chromatography (HILIC) materials for metabolomics and glycomics, restricted access media (RAM) columns coupled with nano LC for peptidomics, immunoaffinity trap columns for targeted proteomics and metal oxide affinity phases for phosphopeptide analysis. However, issues can arise when combining different phases in on-line SPE-LC, e.g. due to solvent incompatibilities between enrichment/separation principles and sample solvent requirements. Consequences can be low recovery and poor resolution, or need for additional instrumentation. On-line SPE-LC with very narrow columns (10-20 μm inner diameters) can be appropriate to obtain maximum sensitivity and information. In such highly miniaturized systems, non-particulate columns are arguably more suited (e.g. monolithic or porous layer open tubular (PLOT) columns) as e.g. hardware contributions resulting in extra column volumes are reduced. Basic SPE-LC systems can be configured/modified to perform quite complex analytical operations, and certain columns, configurations and hardware can improve robustness.
authors.affiliation: Department of Chemistry, University of Oslo, Post Box 1033, Blindern, N-0315 Oslo, Norway.
authors.forename: Magnus
authors.initials: M
authors.lastname: Rogeberg
authors.forename: Helle
authors.initials: H
authors.lastname: Malerod
authors.forename: Hanne
authors.initials: H
authors.lastname: Roberg-Larsen
authors.forename: Cecilie
authors.initials: C
authors.lastname: Aass
authors.forename: Steven Ray
authors.initials: SR
authors.lastname: Wilson
mesh_terms: D000818:Animals; D002853:Chromatography, Liquid / Q000379:methods*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008904:Miniaturization; D012680:Sensitivity and Specificity; D052616:Solid Phase Extraction / Q000379:methods*; D012997:Solvents / Q000737:chemistry
chemical_list: D012997:Solvents
keywords: Bioanalysis; Enrichment; Nano LC; On-line SPE–LC; Selectivity