Ultraviolet native fluorescence detection in capillary electrophoresis using a metal vapor NeCu laser

Ultraviolet (UV) excitation for laser-induced native fluorescence (LINF) detection in capillary electrophoresis (CE) offers impressive performance figures of merit when assaying peptides containing tyrosine or tryptophan residues, catecholamines, indolamines, and a number of other classes of analytes with appreciable fluorescence when excited by LTV radiation. One of the largest drawbacks of native fluorescence detection schemes in CELINF systems has been the expense and the complexity of the lasers required for excitation in the deep UV wavelength range of 200-300 nm. An improved "turnkey" NeCu laser operating at 248.6 nm interfaced to a sheath flow-based CE system obtains a performance similar to that of large frame frequency-doubled Ar ion lasers. The detection limits for serotonin and dopamine (27 nM and 8 μM, respectively, for ∼3-nL injection) are similar to those obtained using a frequency-doubled Ar ion laser at 257 nm (21 nM and 8 μM, respectively). An example of the detection of serotonin-related analytes from a single-cell electropherogram demonstrates the performance of such a system for mass-limited measurements.