Rapid and sensitive detection of trace malachite green and its metabolite in aquatic products using molecularly imprinted polymer-coated wooden-tip electrospray ionization mass spectrometry

In this study, a molecularly imprinted polymer-coated wooden-tip (MIPCWT) electrospray ionization mass spectrometry (ESI-MS) method was developed for rapid and sensitive detection of trace malachite green (MG) and its metabolite in aquatic products. Such a method was realized by applying a silicone-modified acrylate molecularly imprinted emulsion (SMAMIE) onto the surface of wooden tips to specially design a MIPCWT solid-phase micro-extraction (SPME) probe for selective enrichment of MG and its metabolite from aquatic products. Subsequently, a high voltage and some spray solvent were applied to the MIPCWT SPME probe, and ESI was induced for direct MS analysis under ambient and open-air conditions. The MIPCWT-SPME probe exhibits a high enriching capacity of approximately 1500-2000 fold toward MG and leucomalachite green (LMG), with detection limit reaching 0.01 μg L^-1. In addition, a good linearity is obtained for both MG and LMG, with correlation coefficient values (R²) of no less than 0.998. The present method was successfully applied to analyze MG and LMG in real-life tap water, river water and fish samples, and good recoveries in the range of 93-103%, 92-108% and 106-113%, respectively, were found. All of these demonstrated that our developed MIPCWT-ESI-MS method holds great potential for rapid, direct, sensitive, and reliable detection and analysis of trace veterinary drug residues in aquatic products.