title: [Study on multi-photon excited fluorescence combined with capillary electrophoresis].
abstract: This paper describes a new method, multiphoton excitation fluorescence detection combined with capillary electrophoresis separation. The excitation source was a self mode-locked femtosecond titanium-sapphire laser (Spectra-physics Inc.), producing a stream of pulses with a pulse duration of about 100 fs at 82 MHz repetition rate. Its average power was about 200 mW at 750 nm. The laser beam was focused into a thin wall flow cell of capillary electrophoresis. A high numerical aperture objective (100 x NA 1.25) was chosen to focus the laser beam and to collect the fluorescence emitted by detecting molecules. Then the fluorescence was detected by a fast response PMT. All data were acquired and processed by a microcomputer. For three biological molecules, 5HT, FAD and NADH, it was demonstrated that they can be separated and detected efficiently by this method with three-photon and two-photon excitation respectively using only one 750 nm laser beam. The detection limits were 1.0 x 10(-6) mol x L(-1) for 5HT, 7.4 x 10(-7) mol x L(-1) for FAD and 9.8 x 10(-7) mol x L(-1) for NADH using the criterion of three standard deviations above background. The results are much better than those with UV absorption detection by one or two magnitudes.
authors.affiliation: Key Laboratory for Atomic and Molecular Nanosciences of Education Ministry, Department of Physics, Tsinghua University, Beijing 100084, China.
authors.forename: Yun-xu
authors.initials: YX
authors.lastname: Sun
authors.forename: Feng
authors.initials: F
authors.lastname: Zhu
authors.forename: Wan-yun
authors.initials: WY
authors.lastname: Ma
mesh_terms: D019075:Electrophoresis, Capillary / Q000379:methods*; D005182:Flavin-Adenine Dinucleotide / Q000737:chemistry; D005453:Fluorescence; D007834:Lasers; D009243:NAD / Q000737:chemistry; D017785:Photons; D012701:Serotonin / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods*
chemical_list: D009243:NAD; D005182:Flavin-Adenine Dinucleotide; D012701:Serotonin