Sample pretreatment-free rapid determination of difenoconazole in vegetables by swellable hydrogel microneedles

Difenoconazole is a broad-spectrum triazole fungicide that widely used in fruits and vegetables. However, excessive use of difenoconazole may cause extremely adverse side effects on ecosystems and human health. Nevertheless, currently available detection methods require time-consuming, labor-intensive sample preparation, hindering the rapid screening of difenoconazole in agricultural products. In this study, a pretreatment-free immunosensor based on antibody-modified swellable polyvinyl alcohol/chitosan microneedles (MN) and a portable analyzer was fabricated for the on-site determination of difenoconazole. Due to excellent swelling rate and mechanical strength, the sample tissue fluids were rapidly absorbed without crushing, where potential difenoconazole can be selectively enriched. Under the optimal experimental conditions, this MN-driven immunosensor can detect difenoconazole as low as 36.71 ng/mL within 25 min, definitely can satisfy statutory requirements for difenoconazole quantitation. Moreover, the proposed biosensor exhibits high selectivity, good reproducibility (≤9.03 %), well storage stability (>25 days) and reasonable recoveries (99.6 %-119.2 %). Importantly, there are good agreements between results of this work and authorized LC-MS/MS analysis when detecting difenoconazole in spiked as well as blind vegetable samples, suggesting high reliability and practicability. This work not only conveniently detects difenoconazole with enough sensitivity and acceptable accuracy, but also can be extended for rapid on-site screening of other pesticides in vegetables prior to their release to the market.