Analysis of trace malachite green, crystal violet, and their metabolites in zebrafish by surface-coated probe nanoelectrospray ionization mass spectrometry

Malachite green (MG) and crystal violet (CV) are the typical triphenylmethane dyes, which are recalcitrant molecules exerting mutagenic and carcinogenic effects on living organisms. Characterization of the residues of MG, CV, and their metabolites in biological organisms is of importance, especially for in vivo and in situ characterization. In this study, a method for determination of trace MG, CV, and their leuco metabolites in zebrafish by surface-coated probe nanoelectrospray ionization mass spectrometry (SCP-nanoESI-MS) was developed. A microscale solid-phase microextraction (SPME) probe was developed and used for extraction and enrichment of trace MG, CV, and their leuco metabolites in zebrafish after exposure. After that, the loaded SPME probe was directly employed for nanoESI-MS analysis under ambient and open-air conditions. Under the optimum conditions, the method demonstrated good linearity, with correlation coefficient values (r²) no less than 0.9925. The limits of detection and quantification were 0.014-0.023 ng mL^-1 and 0.046-0.077 ng mL^-1, respectively. By using the proposed method, the bioaccumulation of MG and CV in zebrafish was investigated, and the distribution of MG, CV, and their leuco metabolites in different organs of zebrafish was studied. MG, CV, and their leuco metabolites were all found in zebrafish tissues including brain, muscle, heart, and kidney after exposure, with highest concentration in intestine followed in ovary.

Ambient mass spectrometry; Crystal violet; Malachite green; Metabolites; Solid-phase microextraction.