Optimization of the separation of malachite green in water by capillary electrophoresis Raman spectroscopy (CE-RS) based on the stacking and sweeping modes

A capillary electrophoresis Raman spectroscopy (CE-RS) method based on the stacking and sweeping modes are described. A non-fluorescent compound (malachite green, MG; crystal violet, CV) and a doubled Nd:YAG laser (532 nm, 300 mW) were selected as the model compound and light source, respectively. In order to carry out a quantitative and analysis of MG, a monochromator was used to collect the specific Raman line at 1616 cm−1 (the N-φ and C–C stretching, corresponding to 582 nm when the wavelength of the exciting source is 532 nm). The limit of detection (LOD) for MG was 1.6 × 10−5 and 1.1 × 10−5 M, respectively, based on the CZE and MEKC modes. This could be improved to 3.4 × 10−7 and 5.3 × 10−9 M, respectively, when the stacking and sweeping modes were applied. The method was also extended to the determination of MG in an actual sample.