title: Signal enhancement in HPLC/microcoil NMR using automated column trapping.
abstract: A new HPLC NMR system is described that performs analytical separation, preconcentration, and NMR spectroscopy in rapid succession. The central component of our method is the online preconcentration sequence that improves the match between postcolumn analyte peak volume and microcoil NMR detection volume. Separated samples are collected on to a C18 guard column with a mobile phase composed of 90% D2O/10% acetonitrile-D3 and back-flushed to the NMR microcoil probe with 90% acetonitrile-D3/10% D2O. To assess the performance of our unit, we separated a standard mixture of 1 mM ibuprofen, naproxen, and phenylbutazone using a commercially available C18 analytical column. The S/N measurements from the NMR acquisitions indicated that we achieved signal enhancement factors up to 10.4 (+/-1.2)-fold. Furthermore, we observed that preconcentration factors increased as the injected amount of analyte decreased. The highest concentration enrichment of 14.7 (+/-2.2)-fold was attained injecting 100 microL of solution of 0.2 mM (approximately 4 microg) ibuprofen.
authors.affiliation: Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, USA.
authors.forename: Danijel
authors.initials: D
authors.lastname: Djukovic
authors.forename: Shuhui
authors.initials: S
authors.lastname: Liu
authors.forename: Ian
authors.initials: I
authors.lastname: Henry
authors.forename: Brian
authors.initials: B
authors.lastname: Tobias
authors.forename: Daniel
authors.initials: D
authors.lastname: Raftery
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation* / Q000379:methods*; D007052:Ibuprofen / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods*; D009288:Naproxen / Q000737:chemistry; D010653:Phenylbutazone / Q000737:chemistry
chemical_list: D009288:Naproxen; D010653:Phenylbutazone; D007052:Ibuprofen