title: Label-free analysis in chip electrophoresis applying deep UV fluorescence lifetime detection.
abstract: Herein we introduce deep UV fluorescence lifetime detection in microfluidics applied for label-free detection and identification of various aromatic analytes in chip electrophoresis. For this purpose, a frequency quadrupled Nd:YAG (neodymium-doped yttrium aluminum garnet) picosecond laser at 266  nm was incorporated into an inverse fluorescence microscope setup with time-correlated single photon counting detection. This allowed recording of photon timing with sub-nanosecond precision. Thereby fluorescence decay curves are gathered on-the-fly and average lifetimes can be determined for each substance in the electropherogram. The aromatic compounds serotonin, propranolol, 3-phenoxy-1,2-propanediol and tryptophan were electrophoretically separated using a fused-silica microchip. Average lifetimes were independently determined for each compound via bi-exponential tail fitting. Time-correlated single photon counting also allows the discrimination of background fluorescence in the time domain. This results in improved signal-to-noise-ratios as demonstrated for the above model analytes. Microchip electrophoretic separations with fluorescence lifetime detection were also performed with a protein mixture containing lysozyme, trypsinogen and chymotrypsinogen emphasizing the potential for biopolymer analysis.
authors.affiliation: University of Leipzig, Institute of Analytical Chemistry, Leipzig, Germany.
authors.forename: Reinhild
authors.initials: R
authors.lastname: Beyreiss
authors.forename: Stefan
authors.initials: S
authors.lastname: Ohla
authors.forename: Stefan
authors.initials: S
authors.lastname: Nagl
authors.forename: Detlev
authors.initials: D
authors.lastname: Belder
mesh_terms: D046209:Electrophoresis, Microchip / Q000379:methods*; D005990:Glycerol / Q000031:analogs & derivatives / Q000032:analysis; D053844:Lasers, Solid-State; D010647:Phenyl Ethers; D011433:Propranolol / Q000032:analysis; D015203:Reproducibility of Results; D012701:Serotonin / Q000032:analysis; D059629:Signal-To-Noise Ratio; D013050:Spectrometry, Fluorescence / Q000295:instrumentation*; D014364:Tryptophan / Q000032:analysis
chemical_list: D010647:Phenyl Ethers; D012701:Serotonin; C525361:3-phenoxy-1,2-propanediol; D014364:Tryptophan; D011433:Propranolol; D005990:Glycerol