On the potential of forward-scattering degenerate four-wave mixing detection in capillary electrophoresis

The question is addressed, whether in capillary electrophoresis (CE) the la ser-based forward degenerate four-wave mixing (F-D4WM) detection method can become a realistic alternative to conventional ultraviolet (UV) absorption detection. In order to answer this question F-D4WM experiments at 351 nm h ave been performed. As test analytes the herbicides dinitro-ortho-cresol an d dinitro-(tert-butyl)-ortho-phenol (trivial names DNOC and dinoterb, respe ctively) were used without derivatisation. These compounds show moderate ab sorption (molar absorptivity 4000 M-1 cm(-1)) at 351 nm under the condition s (buffer pH 8.2) used for CE separation. The detection limits obtained (1 mu M) were 25-fold better than with on-column absorption detection at 351 n m. This result is shown to be typical for CE, where commonly buffer solutio ns with a high water content are used. For micro-separation systems that ar e compatible with liquid solutions with a low water content F-D4WM detectio n has a much wider potential. (C) 2000 Elsevier Science B.V. All rights res erved.