C. Gooijer et al., Capillary electrophoresis with laser-induced fluorescence detection for natively fluorescent analytes, ANALUSIS, 28(8), 2000, pp. 679-685
Laser-induced fluorescence (LIF) detection systems for capillary electropho
resis (CE) are nowadays widely available. Many classes of analytes show nat
ive fluorescence, but often only upon absorption of short-wavelength UV lig
ht. Unfortunately, most CE-LIF systems make use of visible laser lines so t
hat they can only be applied to analytes that have been chemically derivati
sed with a suitable fluorescent label matching the excitation wavelength. T
his paper illustrates how the applicability of Ce-LIF can be broadened to i
nclude natively fluorescent analytes by employing either UV laser systems o
r multiphoton-excitation. Several pulsed and continuous wave (CW) lasers we
re compared in terms of analytical sensitivity and selectivity; in particul
ar the CW 275-nm line from an adapted Ar+ laser proved very suitable. For i
dentification purposes emission spectra were recorded online. The usefulnes
s of such systems in environmental chemistry is shown for amino- and hydrox
y-substituted naphthalensulphonates in river water samples. Extra spectral
selectivity can be obtained by performing CE-LIF under fluorescence line-na
rrowing conditions using a cryogenic interface. The introduction of high-re
petition rate, femtosecond Ti:sapphire lasers paved the way for two- and th
ree-photon excited LIF detection of a wide array of biologically relevant f
luorophores.