Quantitative analysis of fungicide azoxystrobin in agricultural samples with rapid, simple and reliable monoclonal immunoassay

Spatiotemporal Visualization of Insecticides and Fungicides within Fruits and Vegetables Using Gold Nanoparticle-Immersed Paper Imprinting Mass Spectrometry Imaging

Food safety issues caused by pesticide residue have exerted far-reaching impacts on human daily life, yet the available detection methods normally focus on surface residue rather than pesticide penetration to the internal area of foods. Herein, we demonstrated gold nanoparticle (AuNP)-immersed paper imprinting mass spectrometry imaging (MSI) for monitoring pesticide migration behaviors in various fruits and vegetables (i.e., apple, cucumber, pepper, plum, carrot, and strawberry). By manually stamping food tissues onto AuNP-immersed paper, this method affords the spatiotemporal visualization of insecticides and fungicides within fruits and vegetables, avoiding tedious and time-consuming sample preparation. Using the established MSI platform, we can track the migration of insecticides and fungicides into the inner region of foods. The results revealed that both the octanol-water partition coefficient of pesticides and water content of garden stuffs could influence the discrepancy in the migration speed of pesticides into food kernels. Taken together, this nanopaper imprinting MSI is poised to be a powerful tool because of its simplicity, rapidity, and easy operation, offering the potential to facilitate further applications in food analysis. Moreover, new perspectives are given to provide guidelines for the rational design of novel pesticide candidates, reducing the risk of food safety issues caused by pesticide residue.

Simultaneous Detection of Six Different Types of Pesticides by an Immunosensor Based on Surface Plasmon Resonance

Six pesticides, azoxystrobin, boscalid, chlorfenapyr, imazalil, isoxathion, and nitenpyram, were simultaneously detected by using a surface plasmon resonance (SPR) immunosensor. The working ranges were 3.5 - 19 ng/mL for azoxystrobin, 4.5 - 50 ng/mL for boscalid, 2.5 - 25 ng/mL for chlorfenapyr, 5.5 - 50 ng/mL for imazalil, 3.5 - 50 ng/mL for isoxathion, and 8.5 - 110 ng/mL for nitenpyram. They showed adequate recovery results in tomato samples: 104 - 116% for azoxystrobin, 94 - 101% for boscalid, 90 - 112% for chlorfenapyr, 96 - 106% for imazalil, 107 - 119% for isoxathion, and 104 - 109% for nitenpyram. The correlation coefficient with liquid chromatography (HPLC or LC-MS/MS) using vegetable samples also agreed well: 0.91 - 0.99 as R2 without strong bias, except for nitenpyram for which the SPR immunosensor sensitivity was too low. The SPR immunosensor will have high applicability for pesticide residue analyses in vegetable samples.

Assessment of strobilurin fungicides' content in soya-based drinks by liquid micro-extraction and liquid chromatography with tandem mass spectrometry

Seven strobilurin fungicides were pre-concentrated from soya-based drinks using dispersive liquid-liquid micro-extraction (DLLME) with a prior protein precipitation step in acid medium. The enriched phase was analysed by liquid chromatography (LC) with dual detection, using diode array detection (DAD) and electrospray-ion trap tandem mass spectrometry (ESI-IT-MS/MS). After selecting 1-undecanol and methanol as the extractant and disperser solvents, respectively, for DLLME, the Taguchi experimental method, an orthogonal array design, was applied to select the optimal solvent volumes and salt concentration in the aqueous phase. The matrix effect was evaluated and quantification was carried out using external aqueous calibration for DAD and matrix-matched calibration method for MS/MS. Detection limits in the 4-130 and 0.8-4.5 ng g(-1) ranges were obtained for DAD and MS/MS, respectively. The DLLME-LC-DAD-MS method was applied to the analysis of 10 different samples, none of which was found to contain residues of the studied fungicides.

Analysis of the Fungicide Boscalid in Horticultural Crops Using an Enzyme-Linked Immunosorbent Assay and an Immunosensor Based on Surface Plasmon Resonance

A direct competitive enzyme-linked immunosorbent assay (dc-ELISA) and an immunosensor based on surface plasmon resonance (SPR-sensor) were developed for fungicide boscalid determination in horticultural crops. To produce antiboscalid monoclonal antibodies (MoAb BSC7 and MoAb BSC72) for these assays, a hapten of boscalid was synthesized and conjugated to keyhole limpet hemocyanin for Balb/c mouse immunization. The working range of the dc-ELISA was 0.8-16 ng/mL with MoAb BSC7 and 2.5-120 ng/mL with MoAb BSC72, and that of the SPR-sensor was 17-80 ng/mL with MoAb BSC7. The dc-ELISA and SPR-sensor were compared for their sensitivity in determining boscalid residues at the maximum residue limit of 1-40 mg/kg for horticultural crops in Japan. Recovery of the spiked boscalid was 85-109% by the SPR-sensor and 100-124% by the dc-ELISA. On real tomato samples, the results obtained by both of these immunoassays correlated well with the results obtained by high-performance liquid chromatography.