Rapid Determination Of Malachite Green In Aquatic Products By Nano Electrochemical Sensor

Malachite green（MG）is a kind of drug dye with strong bactericidal effect.MG is not only used to prevent and treat fungal infection,bacterial infection,white disease,melon disease,haemorrhagic disease and so on,but also makes the color of aquatic products look more fresh.MG is rapidly transformed into leucomalachite green（LMG）after entering the animal body.It has been found that MG like compounds have high residue and toxicity,which can produce toxic side effects such as“three causes”.The United States,Japan and Canada stipulate that MG and LMG are forbidden to be detected in edible aquatic products,and China also lists MG as prohibited drug.Therefore,it is of great social significance and application prospect to establish a rapid and efficient method for the detection of MG and its metabolite LMG residues in aquatic products.In this paper,MG or LMG will be determined by three electrochemical methods:self-redox property,enzyme sensor and immunosensor.（1）A nano electrochemical sensor method was developed for the rapid determination of MG in aquaculture water,which was modified with Nafion and MWCNTs composite materials on glassy carbon electrode.The preparation of Nafion/MWCNTs/GC was studied,and the preparation and detection conditions was optimized.The cyclic voltammograms of MG at Nafion/MWCNTs/GC showed that there was a good oxidation peak at 0.57 V potential and no reduction peak,which indicated that the electrochemical reaction of MG was an irreversible oxidation-reduction process.The content of MG was determined according to the different concentration of MG in the LiCl electrolyte solution corresponding to different oxidation peak currents.At the optimum conditions,the oxidation peak currents of MG increased linearly with its concentration in the range of3.0×10^-79.0×10^-6 mol/L,with the limit of detection（LOD）as 6×10^-8 mol/L（S/N=3）.It has been applied to the determination of MG in aquaculture water.The recovery of standard addition is 95.90%⁹8.70%,and the method has practical application value.（2）A nano electrochemical sensor method was developed for the rapid determination of LMG in aquatic products,which was modified with CS and GS composite materials on glassy carbon electrode.The preparation of CS/GS/GC was studied,the preparation and detection conditions was optimized.The electrochemical behavior of LMG was investigated,Cyclic voltammogram of LMG showed that there were two oxidation peaks at 0.79 V and 1.18 V,and a reduction peak at about 0.98 V,which indicated that its electrochemical oxidation was carried out in two steps,but the electrochemical reduction was completed in one step.The content of LMG was determined according to the different concentration of LMG in the LiClO₄ electrolyte solution corresponding to different oxidation peak currents.At the optimum conditions,the oxidation peak currents of LMG increased linearly with its concentration in the range of 1.0×10^-89.0×10^-8 mol/L,with the limit of detection（LOD）as 4.0×10^-9 mol/L（S/N=3）.The method has been applied to the determination of red spot fish.The recovery of standard addition is 99.87%¹02%,and the method has practical application value.（3）A nanoelectrochemical enzyme sensor method was established for rapid determination of MG and LMG in aquatic products,which was modified with CS and GS composite materials on glassy carbon electrode.Glutaraldehyde was used as the immobilization material of butyryl cholinesterase（BuChE）and the preparation and detection conditions was optimized.Meanwhile the influence of MG on BuChE was studied.The content of MG was determined according to the different peak current of Mg inhibiting the catalytic substrate.Under the optimized conditions,the oxidation peak current of the enzyme sensor is linearly related to the concentration of MG in the electrolyte solution in the range of 1.0×10^-71.1×10^-66 mol/L,with the limit of detection（LOD）as 2.8×10^-8 mol/L（S/N=3）.The method has been applied to the determination of red spot fish.The recovery is 96.36%⁹9.78%,and the method provides a new way for the rapid determination of MG residue in aquatic products.（4）A nanoelectrochemical immunosensor method was developed for the rapid determination of LMG in aquatic products,which was modified with CS,GS and Nano-Ag composite materials on glassy carbon electrode,the preparation of CS/GS/Nano-Ag/GC nanoelectrochemical immunosensor was studied,and the preparation and detection conditions was optimized.The content of LMG was determined by the inhibition of Fe（CN）₆^3-/4-oxidation peak current by specific binding of different concentrations of antigen antibody.Under the optimized conditions,the oxidation peak current of the enzyme sensor is linearly related to the concentration of LMG in the electrolyte solution in the range of 0.3⁰.9×10^-9 mol/L（S/N=3）,with the limit of detection（LOD）as 0.4×10^-11mol/L.The method has been applied to the determination of red spot fish.The recovery is85.93%⁹7.60,and the method provides a new way for the rapid determination of LMG residue in aquatic products.