Gas chromatographic/mass spectrometric confirmation of leucomalachite green in catfish (Ictalurus punctatus) tissue.

Abstract

A gas chromatographic/mass spectrometric (GC/MS) method was developed to confirm the presence of leucomalachite green (LMG), a metabolite of the triphenylmethane dye malachite green (MG), in catfish tissue. Residues were isolated according to a previously described liquid chromatographic (LC)/VIS spectrometric analysis of MG and LMG in fish. In our isolation procedure, analytes are extracted from tissue with acetonitrile-buffer, partitioned into CH2Cl2, and applied to neutral alumina and propylsulfonic acid solid-phase extraction cartridges. Before GC/MS analysis, extracts prepared for the LC determinative method are eluted from a cyano solid-phase extraction cartridge, extracted into organic solvent, and concentrated for GC/MS analysis. Selected ion monitoring was performed by using 5 diagnostic ions (m/z 330, 329, 253, 210, and 165) of LMG. The method was validated by confirming LMG in tissue fortified with mixtures of MG and LMG (5 and 10 ng/g each) and in tissue from fish that had been exposed to low levels of MG.