Residue analysis of methoxuron and its breakdown product (3-chloro-4-methoxyaniline) by thin-layer and high-performance liquid chromatography with fluorescence detection

Add time:09/08/2019    Source:sciencedirect.com

Dns derivatization prior to fluorescence detection of phenylurea herbicides (after hydrolysis) and their aniline metabolites was further developed for residue analytical purposes with high-performance (HPLC) and thin-layer chromatography (TLC). Metoxuron and 3-chloro-4-methoxyaniline (CMA) were used as model compounds. An increased fluorescence intensity in TLC was obtained by dipping the plates into paraffin-hexane (2:1). A simple derivatization procedure, viz., addition of Dns chloride, evaporation and dissolution, plus overnight reaction, in the acetonitrile-water mixture used as the mobile phase, was developed for HPLC. The fluorescence intensity of Dns-anilines decreases with increase in the number of halogen substituents, and increases if a methoxy substituent is present. The detection limit of Dns-CMA is about 1 ng in both TLC and HPLC.Residue analyses of CMA and metoxuron in water, potato and soil samples involved acetone or dichloromethane extraction, silica gel clean-up, hydrolysis on a TLC plate (for metoxuron), Dns derivatization and HPLC or TLC evaluation. Retention data and recoveries are presented. The detection limits for CMA are 0.001 mg/kg in water, 0.02 mg/kg in potato and 0.2 mg/kg in soil.

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