Coupling liquid-phase microextraction with paper spray for rapid analysis of malachite green, crystal violet and their metabolites in complex samples using mass spectrometry

Coupling liquid-phase microextraction (LPME) with paper spray mass spectrometry (PS-MS) has been successfully achieved and applied in the analysis of malachite green, crystal violet and their metabolites in complex samples. This technique involved liquid-phase microextraction for the enrichment of target analytes followed by paper spray for direct mass spectrometric analysis under ambient and open-air conditions. Extraction conditions including extraction solvent, volume, time, temperature, pH and salinity were optimized. The proposed method showed enhanced sensitivity, by approximately 100-700 fold, for the detection of target analytes in aqueous samples. The method showed good linearity, with correlation coefficient values (r(2)) of no less than 0.9917 for four target compounds. The limits of detection and quantification of the four target compounds were 2.2-3.1 and 6.5-13.7 ng L-1, respectively. High recovery values of 92.2-112.4% and 93.1-108.6% were obtained at different concentrations of 50 ng L-1 and 500 ng L-1, respectively. The proposed method has been applied for the analysis of four target analytes in real lake water samples, and the experimental results demonstrated that this method was rapid, convenient, economic and friendly to the environment.