Hapten synthesis and a colloidal gold immunochromatographic strip assay to detect nitrofen and bifenox in fruits

Abstract

In this study, we synthesized two haptens similar in structure to nitrofen (NIT), and screened out five monoclonal antibodies with the ability to recognize NIT and bifenox (BIF) by competitive ELISA, with the lowest IC₅₀ values of 0.87 ng mL⁻¹ and 0.86 ng mL⁻¹, respectively. The antibody 5G7 was selected to be combined with colloidal gold to establish a lateral flow immunochromatographic assay strip. This method was shown to qualitatively and quantitatively detect the residues of NIT and BIF in fruit samples. The visual limits of detection for qualitative detection were 5 μg kg⁻¹ and 10 μg kg⁻¹ for NIT and BIF, respectively. The calculated limits of detection for quantitative detection were 0.75 μg kg⁻¹, 1.77 μg kg⁻¹ and 2.55 μg kg⁻¹ respectively, for nitrofen in orange, apple and grapes, and 3.54 μg kg⁻¹, 4.96 μg kg⁻¹ and 5.26 μg kg⁻¹, respectively, for bifenox. Thus the strip assay could be used for rapid analysis of fruit samples.