Determination of Malachite Green by Capillary Electrophoresis with Capacitively Coupled Contactless Conductivity Detection (CE-C4D)

Malachite green (MG) is well known for its strong and stable coloring properties, as well as its effective antibacterial activity. It is a common dye for various materials and an antibacterial in aquaculture. However, MG has been banned in the aquaculture and food industries due to its toxic effects on humans and animals. Therefore, the development of a reliable and efficient method for the determination of MG is necessary. In this study, the capillary electrophoresis with capacitively coupled contactless conductivity detector (CE-C4D) method was used to analyze MG. The analysis was performed using a fused-silica capillary with an internal diameter of 50 µm, a total length of 60 cm, and an effective length of 30 cm. The electrolyte solution was 10 mM histidine/acetic acid buffer at pH 5.5. A hydrodynamic siphoning injection at a height of 15 cm for 30 s was applied. The separation voltage was 20 kV. The method detection limit of MG was 1.5 ppm. The recovery of MG at three concentration levels (i.e., 20, 50, and 100 ppm) ranged from 94.57% to 101.13% with RSD < 5% (n = 5 for each level). The recovery and repeatability of MG obtained by our method satisfied the requirements proposed by the Association of Official Analytical Collaboration (AOAC).