Laser-excited fluorescence detection of gas-phase chromatography eluates

A high-spectral-resolution laser-excited molecular fluorescence gas chromatographic (GC) detection system is evaluated. It utilizes a pulsed supersonic jet expansion to yield very-narrow-bandwidth (e.g. less than or equal to 0.1 nm) fluorescence excitation spectra that may be rapidly scanned via a tunable dye laser. A microcomputer synchronizes the entire system, collects data, performs calculations, and creates visual displays of results. The laser-excited fluorescence detection system was interfaced to a gas chromatograph to exploit both the selectivity of the chromatography and the excellent spectral selectivity of the detector. Fluorescence excitation chromatograms were acquired by monitoring fluorescence emission from selected transition wavelengths characteristic of the GC eluates. The excitation wavelengths were also programmed to change at appropriate retention times to provide greatest selectivities for individual analytes as they eluted, and to allow multiple analytes to be determined in a single elution. Response factors for the system varied appreciably from run to run, which precluded the use of external standard quantitation procedures. However, excellent stabilities for within-run relative response factors were sufficient to allow for good quantitative measurements using internal standard techniques.