An immunochromatographic assay for the rapid detection of oxadixyl in cucumber, tomato and wine samples

Abstract

Oxadixyl is a systemic phenylamide fungicide, used to prevent and control disease caused by phytophthora and downy mildew in a variety of cash crops. In this study, a hapten of oxadixyl was designed and used to prepare a highly specific and sensitive anti-oxadixyl monoclonal antibody (mAb) with a 50% inhibition concentration of 3.68 ng/mL. An immunochromatographic assay (ICA) was developed for screening of oxadixyl residues in cucumber, tomato and wine. The ICA strip provided a visible limit of detection (vLOD) of 1 ng/g and a cut-off value of 20 ng/g in cucumbers and tomatoes and displayed a vLOD of 5 ng/mL and a cut-off value of 100 ng/mL in wine. The calculated limit of detection (cLOD) values of the ICA were 1.45 and 0.55 ng/g for cucumbers and tomatoes and 2.11 ng/mL for wine. The ICA gave recovery rates of 95.4–106.0% for cucumber samples, 96.4–99.5% for tomato samples and 93.0–97.4% for wine samples. Moreover, the test results provided by the ICA were highly consistent with those of LC/MS. These results and data indicated that the ICA was an effective and practical method for rapid and high-throughput detection of oxadixyl residues in cucumber, tomato, wine and other food samples.