Malachite green (MG) Detection Knowledge

Malachite green (MG) is a metallic-looking crystal.It dissolves in water easily as a blue-green solution.It is a toxic chemical primarily used as a dye and has been found very effective in treating parasites,fungal infections, and bacterial infections in fish and fish eggs. On uptake, MG is rapidly reduced into leucomalachite green (LMG) and deposited in the fatty tissue of the fish with little MG remaining.

MG can cause significant health risk for humans who eat contaminated fish. For example, it can cause liver tumor formation and is suspected of carcinogenesis. The United States, Japan, China,the European Union, and many other countries have already banned MG in fishery. Due to its low cost and antifungal effectiveness, MG is still being used illegally as indicated in the European Rapid Alert System for Food and Feed. HPLC with UV detection has been used to analyze MG and LMG. Figure 1 shows the structure of the two compounds. Loss of conjugation by reduction changes the chromaphore of LGM significantly. To obtain the sum of both, the method employs post-column oxidation with PbO₂ to convert LMG to MG, thus providing a sum of both compounds. Most recently, LC/MS has been used to both meet the EU confirmation criteria and provide quantitative results for both compounds without the need for post-column oxidation. In this application, a simple and sensitive method for simultaneously determining MG and LMG is presented. The LC/MS/MS method’s LOQ is 0.01 μg/Kg, which easily meets the import requirement set by Japan or the EU.