Extraction of malachite green, crystal violet and their leuco metabolites from salmon using QuEChERS and EVOLUTE CX for LC-MS-MS analysis

Malachite green (MG) and crystal (gentian) violet (CV) are triphenylmethane dyes used in aquaculture as fungicides and ectoparasiticides. They are rapidly metabolised to the leucomalachite green (LMG) and leucocrystal (gentian) violet (LCV) metabolites that persist in fish tissue. MG and CV are banned in many countries due to their mutagenicity and carcinogenicity, but may still be used illegally.

Monitoring methodologies must be able to detect the compounds at 1 ng/g (US) or 2 ng/g (EU). In order to meet these LODs for complex matrices such as oily fish, and the low UV absorbance of the leuco forms, LC-MS-MS is the analytical method of choice. This application note focuses on ease of use when compared to other methods and describes a QuEChERS based approach incorporating the use of aluminium oxide in enhanced dispersive SPE to reduce the levels of fat in the final extract. Additional cleanup is provided by polymeric EVOLUTE SPE columns, and the resulting extract demonstrated low ion suppression. Analyte recoveries of 60-105%, with low rsds, are achieved. The method is also applicable to brilliant green.