NEAR-INFRARED LASER-INDUCED FLUORESCENCE DETECTION IN COLUMN LIQUID-CHROMATOGRAPHY - A COMPARISON OF VARIOUS LASERS AND DETECTION SYSTEMS .2. PULSED LASERS

The applicability of two pulsed lasers, a XeCl-excimer/dye laser and a Nd:YAG/dye laser combination, as excitation sources for near-infrared (NIR) laser-induced; fluorescence (LIF) detection in column liquid chromatography (LC) is studied. Using gradient LC, the best detection limit for the model compound, disulphonated aluminum phthalocyanine (AlPcS2), is 4 . 10(-12) M obtained using the excimer/dye laser combination. This value is about 10-fold lower than obtained with the Nd:YAG laser, but 20-fold higher than for CW diode laser excitation, as reported in Part I of this study [J. Chromatogr. A, 695 (1995) 175]. Because of excitation saturation the optimum results were obtained using only a fraction of the available power. A detailed theoretical discussion is presented which underlines the experimental results and provides insight into the factors that determine the detection limits.