PESQUALSE

Context

A seed is a high-tech product nowadays, combining genetic progress with increasingly complex and effective chemical protection. It is vital to save seed and to protect each seed - and thus each seedling - properly from pathogens and pests. Seed treatment with plant protection products is only effective if the active substance is applied at the target rate and distributed evenly over the seeds in a lot. The latter aspect is particularly significant in the case of “top-of-the-range” fungicides and insecticides used at a low rate and in precision drilling. Too low a rate on a seed can impair the biological efficacy, whereas too high a rate increases the risks of phytotoxicity and is neither economically nor environmentally profitable. Despite demands from the industry, verification of the correct application of plant protection products to seeds has until now been hampered by the lack of a rapid, relatively inexpensive analytical method, especially since the time span between seed treatment and drilling is fairly short as a rule. Analytical results for industrially treated commercial seeds too often show the quality of the plant protection treatments to be very patchy, falling short of the sector’s expectations. Directive 91/414/EEC concerning the placing of plant protection products on the market in Europe requires scientific data on the quality of seed treatments (product adhesion and distribution over the seeds).

Objectives

This project aims to develop, optimise and validate analytical methods using chromatography ((U)HPLC and GC) to determine the active substances on seeds treated with plant protection products. Such methods should permit measurement of the average active substance content of a lot of treated seeds and determination of the active substance content of individual seeds in order to assess treatment distribution. The validated analytical methods can then be used to assess the quality of seed treatments within the framework of registration of plant protection products, commercial seed testing or product effectiveness trials. The results of the work will lead to an improvement in the quality of seed treatments and enable standards to be drafted to fill the present gap.

Description of tasks

Over the past ten years around twenty analytical methods using high performance liquid chromatography (HPLC) or gas chromatography (GC) have been developed at the laboratory to determine (identify and quantify) pesticides on treated seeds in terms of both average rate and individual seed rate. The methods have been optimised as regards the pesticide extraction step using an appropriate solvent and the chromatographic determination step ((U)HPLC-DAD and GC-FID). The methods have also been validated in accordance with European and international recommendations. The following parameters have been determined: specificity, linearity of detector response, repeatability, accuracy (recovery yields and extraction effectiveness), limit of detection (LOD), limit of quantification (LOQ) and pesticide stability in solvents and extracts.

Expected results

Most of the analytical methods have been validated in accordance with the OECD principles of Good Laboratory Practice (Certificate GLP C04). These validated methods enable treated seed lots to be analysed to obtain scientific data for plant protection product registration or to check the quality of the treatments applied to commercial lots or lots used in product effectiveness trials. Chromatographic methods may be regarded as benchmark methods for pesticide determination in seeds, for both average rate and individual seed rate. These methods are specific, accurate, repeatable and sensitive, but at the same time they are lengthy, destructive and relatively expensive. They also require considerable resources and a specialist team. This makes them unsuited to control chain use. As the time that elapses between seed treatment and drilling is very short as a rule, rapid, effective quality control is required.

Contribution

The Plant Protection Products and Biocides Physico-chemistry and Residues Unit is in charge of development, optimisation and validation of chromatographic ((U)HPLC and GC) for determining active substances on seeds treated with plant protection products (average content and treatment distribution). They will submit a full report to the clients for the purposes of plant protection product registration or supporting a research project or monitoring data.