Study On Upconversion Fluorescence Labeling Immunoassay For The Detection Of Dimethyl Phthalate

In this study, a fluorescence immunoassay for the detection of dimethyl phthalate(DMP) was developed using NaYF4:Er3+,Yb3+ upconversion nanoparticles (UCNPs) as fluorescence signal carrier and magnetic polystyrene microspheres as separation carrier,respectively. This method was then applied to the analysis of the dimethyl phthalate in food samples.The coating antigen (DMP-OVA) was prepared using the glutaraldehyde coupling method. The hydrothermal method was used to the synthesis of NaYF4 : Er3+ , Yb3+upconversion nanoparticles (OA-UCNPs) with uniform particle size. The ligand exchange method was used to prepared water-soluble upconversion nanoparticles (PAA-UCNPs). The fluorescence signal probe and the sensing probe were obtained via the active ester method.The optimal adding volume of the sensing probe, the signal probe and the DMP standards(or diluted sample solutions) was 100 ?L and the reaction time was 50 min. The detection limit of the proposed method for DMP was 1 ng mL-1 and the linear range of assay ranged from 1 ng mL-1 to 1000 ng mL-1, and this assay showed no cross-reactivity with other DMP analogues. The sample pretreatment step of assay was simple. The white wine and beverage samples were diluted 5-fold with sample dilution buffer, and then analyzed using the proposed method directly. And the vegetable samples were diluted 5-fold with sample dilution buffer to detect after a simple extraction treatment. The recoveries of the vegetable samples (cauliflower, angle melon, cabbage), the beverage samples (sports drink, tea drink,milk drink, mango juice) and white wine samples (42°, 56°, 62°) were in ranges of 79.1-124.0% at three spiked concentration of 10, 100, 500 ng g-1 (ng mL-1). And the results of the developed fluorescence immunoassay exhibited good correlation with GC-MS results(R2=0.9721).The developed fluorescence immunoassay based on upconversion nanoparticles and magnetic polystyrene microsphere showed high sensitivity, good specificity, weak background interference and easy accessibility, it was suitable for rapid quantitative determination of the dimethyl phthalate in food samples.