Analysis of active seedcare substances in pelleted sugar beet seeds – method development and validation in a round-robin study

A method by high-performance liquid chromatography (HPLC) with UV-detection was developed for the determination of the active substances hymexazol, tefluthrin, sedaxane, fludioxonil, metalaxyl-M, thiamethoxam, imidacloprid, clothianidin and b-cyfluthrin in pelleted sugar beet seed. The method performance was investigated in a round-robin study in 2021. In this study, ten laboratories analyzed 15 different seed samples, provided by five manufacturers. For each sample, two representative portions of 100 pelleted seeds were analyzed. In general, the highest recovery rates were obtained using an extraction solvent consisting of 95% acetone, 4% water and 1% phosphoric acid and this solvent was therefore selected as the preferred solvent for the simultaneous extraction of the different active substances from the pelleted seeds. However, slightly higher recovery rates for hymexazol were obtained using a mixture of 80% acetone, 19% water and 1% phosphoric acid. This solvent remains an alternative for the analysis of hymexazol. The presented and validated method may serve as an internationally recognized reference method for the analysis of different fungicides and insecticides in pelleted sugar beet seeds from different origin.