AuNPs-based lateral flow immunoassay for point-of-needs analysis of four neonicotinoids in tea samples: Effects of grinding degrees, solvent types and contents on extraction efficiency

Abstract

The higher extraction efficiency of analytes is crucial for developing immunoassays with high accuracy. Here, we evaluated the extraction efficiency of neonicotinoids in tea samples in terms of grinding degrees, extraction solvents types and contents. Fragments for fresh tea leaves (1 g, 5–10 mm2) or tea powder (1 g, 35 mesh) for commercial tea was extracted with 100 % methanol. The extraction (1 mL) was diluted 10-fold with buffer solution, and then submitted to gold nanoparticles-based lateral flow immunoassay. This optimal extraction protocol exhibited a higher extraction efficiency (72.4–99.3 %) for the positive neonicotinoids samples. The cut-off values of lateral flow immunoassay were 0.325 or 0.65 μg/g, 0.3 or 0.45 μg/g, 0.3 or 0.45 μg/g, 0.03 or 0.06 μg/g for thiamethoxami, clothianidin, acetamiprid and midacloprid in fresh tea leaves and commercial tea. In summary, this proposed lateral flow immunoassay can be used as the point-of-needs analysis method for four neonicotinoids in tea.