Detection Of Triphenylmethane Residues In Aquatic Products Based On Rare Earth Complex Fluorescence Method

Malachite Green（MG）is a synthetic triphenylmethane dye that is widely used in the aquaculture industry because of its bactericidal and insecticidal effects.However,due to its high residue,toxicity and teratogenicity,it can cause irreversible damage to aquatic products and human organs and cells.Therefore,the use of MG in aquaculture is explicitly prohibited in China.However,due to the easy access to MG and its bactericidal effect,it has been repeatedly banned in the aquaculture industry.The conventional methods for detecting MG include liquid chromat ography,enzyme-linked immunoassay and electrochemical methods,although these methods are widely used because of their high sensitivity and selectivity.However,their expensive equipment,complex material preparation and the need for specialist personnel to operate the assay have limited the application of these methods for rapid detection.Therefore it is important to find a fast and efficient method for MG detection.Rare earth complexes are very suitable for food analysis as a stable fluorescent probe with large Stoke shift,narrow fluorescent characteristic peaks and high ion luminescence efficiency.In this thesis,the principle that malachite green can undergo fluorescence resonance energy transfer（FRET）with rare earth complexes leading to the fluor escence burst of the complexes was used to establish a rapid method for the detection and identification of MG and triphenylmethane drugs in aquatic products.The main part of the thesis research consists of the following two parts.In the first part,a rare earth complex Eu（TTA）₃phen was synthesized using the rare earth ion Eu³⁺as the central ion,α-thiophenecarbonyl trifluoroacetone（TTA）and o-phenanthroline（phen）as organic ligands,and anhydrous ethanol as the solvent.the rare earth complexes were investigated by thermogravimetry,infrared spectroscopy,elemental analysis,X-ray powder diffraction,fluorescence lifetime,UV-visible spectroscopy and fluorescence spectroscopy.The composition,thermal stability and fluorescence properties of the rare earth complexes were characterised by thermogravimetry,infrared spectroscopy,elemental analysis,X-ray powder diffraction,fluorescence lifetime,UV-Vis spectroscopy and fluorescence spectroscopy.The fluorescence spectra showed that the rare earth complexes emitted the characteristic fluorescence of Eu³⁺ ions at 535 nm,595 nm,615 nm,645 nm and 695 nm,especially the fluorescence at 615 nm overlapped with the UV absorption peak of MG allowing the complexes to FRET with MG.The fluorescence lifetimes of 421.63 μs and 269.66 μs before and after the additio n of 1 μmol L^-1 MG also indicated that MG could cause fluorescence burst of rare earth complexes.The fluorescence response to MG was achieved within 1 min after optimisation of the reaction conditions.T he rare-earth complexes showed good selectivity for MG and were able to quantify MG at concentrations ranging from 0.1-70μmol L^-1 with a detection limit of 0.023 μmol L^-1（3σ/k,n=9）.The spiked recoveries of MG in actual water samples and aquatic product s using the complexes ranged from 89.2% to 98.6%,indicating that the prepared rare earth complexes can be used as fluorescent probes for the detection of MG residues in aquatic products.The rare earth complexes prepared in this thesis use the FRET effect to detect MG,achieving simple preparation conditions,rapid detection process and accurate detection results,providing a new option for the rapid detection of MG in aquatic products.In the second part,four rare earth complexes were prepared as fluoresc ence sensing units using Eu³⁺ and Tb³⁺ as the central rare earth ions and benzoic acid（BA）,furoic acid（2-FA）,α-thiophenecarbonyl trifluoroacetone（TTA）and o-phenanthroline（phen）as organic ligands to construct a four-channel fluorescence sensing matrix for the identification of MG in aquatic products.A 4*6*5 fluorescence data matrix was obtained after five parallel experiments.The fluorescence data matrix was analysed by principal component analysis（PCA）and linear discriminant analysis（LDA）to es tablish fingerprint profiles for the identification of triphenylmethane drugs in aquatic products.The results showed that the LDA method gave better results than the PCA method,with the information extraction rate of the fluorescence sensing matrix being greater than 95% at 10-7,10-6 and 10-5 μmol L^-1 concentrations.And the accuracy of identification in fish samples was 97.38%,indicating that the fluorescence sensing matrix constructed with rare earth complexes can accurately distinguish the six triphe nylmethane drugs in fish samples and can be used for the qualitative and quantitative analysis of triphenylmethane drugs in aquatic products.