Cesare Marucchini

Molecular structure and stereoelectronic properties of herbicide sulphonylureas.

MO theoretical calculations were used with the aim to investigate the electronic properties of a number of sulphonylureas 1-8 which are employed as antifeedants. Quantum chemical descriptors [electron density, molecular electrostatic potential (MEP), the topology of frontier orbitals and reactivity index] were determined for these compounds, aimed both to obtain a deeper insight in their mechanism of action and to correlate these properties with their activity as inhibitors of ALS synthase.

An analytical method for the determination of fluazifop-butyl and fluazifop residues in soil

A method is described for the analysis of soils for residues of the herbicide fluazifop-butyl and its breakdown product fluazifop. Fluazifop-butyl undergoes hydrolysis in the soil to fluazifop, which also has herbicidal activity. A procedure initially using dichloromethane and then methanol+aqueous sodium hydroxide for extraction has been developed and gives good recoveries of both fluazifop-butyl and fluazifop in the 0.01–5 mg kg−1 range. After clean-up, high-performance liquid chromatography with u.v. detection at 245 nm or gas-chromatography with mass framentography were used to determine the residue concentrations. The limit of detection was 0.05 mg kg−1 when h.p.l.c. was used and 0.01 mg kg−1 when g.c.-m.s. was used.

Determination of N‐(3‐ethylsulfonyl‐2‐pyridinyl)‐4,6‐dimethoxy‐2‐pyridineamine in soil after treatment with rimsulfuron

An analytical procedure to detect N-(3-ethylsulfonyl-2-pyridinyl)-4,6-dimethoxy-2-pyridineamine, a degradation product deriving from the hydrolysis of rimsulfuron in soil, has been developed. The analytical standard was prepared by basic hydrolysis of rimsulfuron at pH 9 and purification on a silica gel chromatographic column. The compound obtained was stable at high temperature, thus enabling determination by gas chromatographic analysis. Soil samples were extracted with acetonitrile, purified with a SPE C18 cartridge and analysed using both nitrogen phosphorus (NPD) and mass spectrometer detectors. The analytical procedure described proved to be sensitive and reproducible. Recoveries varied from 84 to 90%. The limit of sensitivity was 0.001 mg kg -1 .