Highly sensitive atrazine fluorescence immunoassay by using magnetic separation and upconversion nanoparticles as labels.

A high-sensitivity fluorescence immunoassay for atrazine was established. It is making use of hydrophilic NaYF4:Yb/Er upconversion nanoparticles (UCNPs) conjugated to the anti-atrazine antibody as signal probe, and of polystyrene magnetic microspheres (PMMs) conjugated to the coating antigen as the capture probe. The coating antigen on the capture probe competes with atrazine for binding to the antibody on the signal probe to form the immuno complex. The complex is separated from the test system by magnetic action, and its green fluorescence is then measured at excitation/emission wavelengths of 980/552 nm using a fluorescence spectrophotometer equipped with an external 980 nm laser. The method was applied to the determination of atrazine in corn, rice, sugar cane juice, and river water. The immunoassay has a linear range that extends from 0.005 to 10 μg·L-1. The assay also recognizes propazine and prometryn, and it therefore can be applied to detect these three herbicides simultaneously. Sugar cane juice and river water samples can be analyzed directly without any pretreatment. The detection limits for atrazine are 2 ng·L-1 in sugar cane juice and river water samples, and 20 ng·kg-1 in corn and rice samples. The recoveries of spiked samples range from 84.7 to 113.6%. Graphical abstract A sensitive fluorescence immunoassay combining magnetic separation for the detection of atrazine in cereal, juice, and water samples using NaYF4:Yb/Er upconversion nanoparticles as labels.