Wavelength-resolved laser-induced fluorescence detection in capillary electrophoresis: Naphthalenesulphonates in river water

Capillary electrophoresis (CE) is combined with wavelength-resolved laser-induced fluorescence detection for the environmental analysis of naphthalenesulphonates (NS) in river water samples. The method enables the detection and the identification of non- as well as hydroxy- and amino-substituted NS. An approximate 30-fold sample concentration is performed by off-line solid-phase extraction prior to the CE separation. The native-fluorescent NS are excited at 280 nm or 325 nm by an excimer dye laser combination providing tunable UV radiation. Wavelength-resolved fluorescence-emission spectra are recorded on line by an intensified diode-array detector mounted on a spectrograph. Since the emission spectra are strongly affected by the type and pattern of substitution, they provide much structural information. In combination with migration times identification is possible, if standards are available. The low to sub-mu g l(-1) detection limits achieved enabled the identification and quantitation of two trisulphonate and an amino-disulphonate NS in River Elbe samples. The data obtained satisfactorily agree with those obtained by ion-pair HPLC.