| In recent years, more concerns are aroused to the safety of aquatic products due to the fishery drugs residue. It is related to people’s physical health, fishermen’s income and social stability. Fishery drugs residue is one of the most serious hazard factors of China’s aquatic product, malachite green is one typical kind. Their functional trityl can cause liver cancer, so it is classified as class 2 carcinogens by the international agency for research on cancer. And although the country has made clear the use of these drugs is disabled, but due to the need of the fish disease prevention, some farmers in the process of breeding often misuse of banned drugs such as malachite green, these drugs residues in fish muscles or organization, often leading to the malachite green residue in aquatic products exceeds the limit standard..This study aimed to develop rapid, sensitive and steady detection methods of malachite green residues in the aquatic product in order to promote the healthy development of aquaculture, and help to establish and improve the guarantee system of the quality and safety. First, we develop a colloidal gold immunochromatographic assay strip for rapid detection of Malachite green (MG) residues in aquatic products and immunogold-silver staining method was employed to improve the sensitivity of the assay strip. This method was based on colloidal gold immunochromatography technology which involved the competition method and used nitrocellulose (NC) membrane as the carrier, The marker protein was malachite green monoclonal antibody. The colloidal gold nanoparticles with diameter of 20 nm were selected to mark the antibodies. The optimum pH was 9.0 and the optimum combination condition was that 1 mL of colloidal gold was combined with 15μg antibodies. The successfully marked antibodies were diluted in 1:10 proportion and 20μL of the antibodies was taken out and fixed on the glass fiber membrane pretreated by PBS (0.01 mol/L,10% sugar,10% Tween-20) to formthe colloidal gold pad. The concentration of antigen and secondary antibody was3 mg/mL and 0.7 mg/mL, respectively. The limit of detectionof this strip for MG was 0.2 ng/mL by conducting a silver enhanced colloidal gold assay to enhance the original signal and this approach was applied to the practical detection of fish samples. The detection time of the whole procedure was approximately 10 minutes, and the test results had good reproducibility. The strip kept stable after storage for 90 days at room temperature. Therefore, this method provides a potential strategy for rapid detection of MG residue in aquatic products.Another rapid detection method was also developed based on electrochemical technology. Malachite green (MG) can risean oxidation peak at the reduced graphene oxide (rGO) modified glassy carbonelectrodes around 0.45 V in pH 7.0 phosphate buffer solution within the potential window from 0.20 V to 0.80 Vin this study. Owing to the unique properties of rGO, the modified eletrode exhibits obvious superiority in detection of MG since it enhances the oxidation peak current of MG significantly. When 1.2×10-5M sodium dodecyl sulfate (SDS) is added in the solution, the peak at 0.45 V disappears, and a bigger oxidation peak occurs at 0.52 V. Parameters influencing the voltammetric response of MG are optimized. Under the selected conditions (i.e. preconcentration for 350 s at -0.3 V, in 0.10 M pH 7.0 phosphate buffer containing 1.2×10-5M SDS), the anodic peak current is proportional to MG concentration in the range of 7 to 3000 μg/L with a detection limit of 9×10-10 M. The regression equations is:ipa=0.543c+0.186 (ipa in μA, c in mg/L, r=0.993). A relative standard deviation (RSD) of 3.2% is obtained for the detection of 1 mg/L MG (n=10), suggesting this modified electrode has excellent reproducibility. Meanwhile, the oxidation peak potential is relatively small when compared with other methods which make it easier to occur oxidation reaction. Based on the experimental results, a sensitive and simple electrochemical method was developed for the determination of MG. Therefore, this newly proposed method indicates a promising tool for rapid detection of MG. |
PDF Full Text Request