New Analytical Methods For The Determination Of Triphenymethane Dyes In Aquatic Products And Environmental Water

Malachite green(MG) and crystal violet(CV), which are belong to triphenymethane dyes, are efficient against protozoal and fungal infection. They have been used widely in aquaculture to treat fish water mildew, black gill disease and parasitic disease, etc. MG and CV are readily absorbed by aquatic animal and metabolically reduced to lipophilic leucomalachite green(LMG) and leucocrystal violet(LCV). Due to the potential hazards on human health and environment, MG, CV, LMG and LCV have been prohibited to be used in aquaculture by many countries such as China, America and European Union, etc. However, the abuse of MG and CV often happens because of their cheapness and high effectiveness. Therefore, it is very important to develop sensitive and accuracy methods for quantitative determination of MG, CV, LMG and LCV.(1) A novel three – dimensional spectrofluorimetric method has been developed for the simultaneous determination of MG, CV, LMG and LCV by combining the sensitivity of molecular fluorescence and the selectivity of the second-order calibration. Residues of MG, CV, LMG and LCV were simultaneously extracted from fish and shrimp muscle with acetonitrile. The non-fluorescent CV and MG were then reduced to the corresponding fluorescent LMG and LCV by reacting with sodium borohydride. After separation and preconcentration with dispersive liquid-liquid microextraction technique, the extracts were analyzed by using excitation-emission matrix fluorescence coupled with second-order calibration methods based on parallel factor analysis(PARAFAC) and alternating trilinear decomposition(ATLD) algorithms. The limits of detection obtained were 2.21- 2.65 ng g-1 by PARAFAC and 2.30-2.86 ng g-1 by ATLD, respectively. The developed method was successfully applied to simultaneous determination of the four analytes in grass carp and shrimp samples with recoveries of 90.53 – 103.03% for PARAFAC and 90.40 – 102.75% for ATLD. The accuracy of this novel method was also verified by high performanceliquid chromatography(2) Boron doped molecularly imprinted polymer(BMIP) modified carbon paste electrode(CPE) was developed to establish a new electrical analytical method which used differential pulse voltammetry(DPV) for determination of MG in water sample. B3+ as dopant could generate Lewis acid sites in the imprinted polymer, which could interact with template molecule. Compared with CPE modified with boron free MIP(B-free MIP) and non-MIP(NMIP), the BMIP showed high recognition ability and affinity for MG. The component and morphology of BMIP were characterized by scanning electron microscopy and the performance of CPE modified with BMIP(BMIP – CPE) was investigated by cyclic voltammetry, DPV and electrochemical impedance spectroscopy. Under optimal conditions, the peak currents by DPV were found to vary linearly with concentrations of MG in the range from 0.5 to 70.0 μmol L-1 with a detection limit of 0.13 μmol L-1. This sensor was successfully applied to detect MG in water samples with acceptable recoveries of 96.3% to 103.8%. In addition, the BMIP-CPE shows enough stability and good reproducibility for the determination of MG.