Sensitive and Rapid Detection of Capsaicinoids in Edible Oils by Lateral Flow Immunoassay with Quantum Dot Beads

To establish a lateral flow immunoassay (LFIA) based on quantum dot beads (QBs) for the rapid and quantitative detection of capsaicinoids (CPCs) in edible oils.

QBs were used as fluorescent probes to label antibodies, and experimental conditions such as buffer pH, the amount of labeled antibody, fluorescent probe dosage, and coating antigen concentration were optimized to establish a novel method for the quantitative detection of CPCs.

The optimal reaction conditions were as follows: buffer pH 7.5, 30 μg of antibodies labeled, 2 μL of fluorescent probe, and coating antigen concentration 0.5 mg/mL. Under the optimal conditions, the half maximal inhibitory concentration (IC₅₀) for CPC in the buffer solution was 0.022 ng/mL. The method was linear over the concentration range of 0.009–0.054 ng/mL. The limit of detection (LOD) for CPCs in edible oil samples was 0.14–0.47 µg/kg. The recoveries in spiked samples ranged from 77.6% to 115.2%, with a coefficient of variation (CV) of less than 8.0%. The cross-reaction rates with CPC analogues were less than 0.1%. When the method was applied for the analysis of 20 edible oil samples containing different amounts of CPCs, the results were well correlated with those of liquid chromatography-tandem mass spectrometry (LC-MS/MS)(R² > 0.90).

The QBs-LFIA method is highly sensitive, specific and reliable, and is suitable for the rapid on-site detection of CPCs in edible oil samples.