Determination of Atrazine in Vegetable Samples Using a Dipstick Immunoassay Format

A dipstick assay format for atrazine analysis in vegetable samples is described. The analytical method consists in a fast extraction procedure followed by a test based on the use of Immobilon-P strips as antibody coating support. The atrazine quantification was carried out measuring the dot colour by a spectrophotometer. Thus atrazine could be detected in a concentration range 0.16-475.0 µg L⁻¹ with an I₅₀ of 2.04 µg L⁻¹. For direct quantification of vegetable samples, those were extracted by blending 5 g in 10 mL of MeOH for 10 min followed by a vacuum filtration through 0.45 µm nylon filters. To avoid erroneous atrazine results, all samples and standards were run in 50% of MeOH which decreased the assay sensitivity by ten fold (I₅₀ = 21.09 µg L⁻¹). Therefore, the proposed methodology was able to perform atrazine analysis under established EU MRL. The samples could be measured directly without any prior concentration or clean-up steps. Recoveries (75-105%) were in agreement with those obtained by a reference method (multiresidue extraction-GC/MS quantification). The feasibility of automated immunoreagent dispenser was also demonstrated.