Dissipation and residue determination of fluopyram and its metabolites in greenhouse crops

BACKGROUND

Fluopyram is a pesticide widely used in tomato and cucumber crops cultivation to control fungal diseases that develop especially in environments with moderate temperatures and high humidity, such as in a greenhouse. The pathway of fluopyram dissipation has been monitored in cucumber and cherry tomato under greenhouse conditions.

RESULTS

In the greenhouse trials, cherry tomato and cucumber were treated by irrigation water with the commercial product at the manufacturer's recommended dose and double dose. High-resolution mass spectrometry (HRMS) coupled to ultra-high-performance liquid chromatography (UHPLC) has been selected as the technique to obtain the identification of fluopyram and metabolites. The fate of fluopyram in greenhouse tomato and cucumber was investigated over 44 days. The metabolic pathway of fluopyram was: in a first step there was a primary transformation to fluopyram-7-hydroxy and fluopyram-8-hydroxy, isomeric compounds, and in a second phase to fluopyram-benzamide and fluopyram-pyridyl-carboxylic acid. The behavior of fluopyram does not fit any type of kinetic classical model of degradation.

CONCLUSIONS

Greenhouse trials revealed that the fluopyram is a very persistent compound, and their terminal residues do not exceed maximum residue level (MRL) at the end of the study. © 2020 Society of Chemical Industry.

Evaluation of the behaviour of propoxycarbazone herbicide in soils and water under different conditions. Post-targeted study

The aim of this study is to understand the levels and behaviour of the herbicide propoxycarbazone in environmental compartments, which are poorly characterized considering degradation products that might reach either surface water as groundwater or soil samples. To this end, an analytical method, based on ultra-high performance liquid chromatography (UHPLC) coupled with Orbitrap mass spectrometry (MS), has been developed to determine the parent compound and its transformation products in soils and water. In addition, a set of laboratory trials has been designed to address the dissipation process of propoxycarbazone formulation in both environmental substrates. The study revealed that the dissipation in water followed a first order kinetics and a non-linear "First Order Multi Compartment" model (FOMC) to soil. Relevant advances have been also achieved in terms of the analytical methodology, as far as the UHPLC-Orbitrap-MS technique allows the development of a retrospective screening of pesticide transformation products in water and soils. For this purpose, an accurate-mass database has been built and used for the post-run screening analysis with 9 transformation products. Photodegradation presumably plays an important role in the dissipation of propoxycarbazone. The results of UHPLC-Orbitrap-MS revealed that four transformation products were formed during the degradation process of the herbicide.