Paola Fidente

Determination of neonicotinoid insecticides residues in bovine milk samples by solid-phase extraction clean-up and liquid chromatography with diode-array detection

In this paper we have developed an analytical method for the simultaneous determination of four nicotinoid insecticides [acetamiprid (ACT), imidacloprid (ICL), thiacloprid (TCL) and thiamethoxam (TMX)] in bovine whole milk. These analytes were extracted, in a single step with dichloromethane, from fortified milk samples, using Chem Elut cartridges, containing diatomaceous earth material. Insecticides determination and quantification were performed by HPLC with diode-array detection (DAD). Average recoveries of the four insecticides from bovine milk samples were between 85.1 and 99.7% at spiking levels 0.01, 0.05 and 0.1 mg kg(-1). Relative standard deviations (RSDs) were no larger than 10% for all of the recovery tests. The calculated limits of quantitation (LOQ) ranged from 0.01 to 0.04 mg kg(-1) for the four insecticides, being equal to or lower than the maximum residue limits (MRLs) established by European legislation (0.01-0.05 mg kg(-1)). The developed method is linear at concentrations within the tested interval, with coefficients of determination higher than 0.9990. According to Commission Decision 2002/657/EC, decision limit (CCalpha) and detection capability (CCbeta) have been calculated. The proposed method is rapid, simple and could be utilized for the routine analysis of pesticides residues.

Development and validation of a solid-phase extraction method coupled to high-performance liquid chromatography with ultraviolet-diode array detection for the determination of sulfonylurea herbicide residues in bovine milk samples

This study proposes a fast, simple and sensitive liquid chromatography diode array detector (LC/UV-DAD)-based method for the simultaneous determination of eight sulfonylurea herbicides (bensulfuron methyl, chlorsulfuron, metsulfuron methyl, primisulfuron methyl, rimsulfuron, thifensulfuron methyl, triasulfuron and tribenuron methyl) in bovine whole milk at concentrations lower than the default limit of 0.01 mg kg(-1) allowed by current legislation (Regulation EC/396/2005 and following Annexes). An effective one-step solid phase extraction (SPE) and clean up procedure was defined with use of Chem Elut cartridges, providing good recoveries for all the analytes tested and with no matrix effects affecting method accuracy. Separation of herbicides was obtained on a C(18) column by acetonitrile- water gradient elution. Method validation has been performed according to European Commission Decision 2002/657/EC criteria, in terms of linearity, recovery, precision, specificity, decision limit (CC(α)) and detection capability (CC(β)). Typical recoveries ranged between 78.4% and 99.7%, at the maximum residue limits (MRLs) levels established by Regulation EC/396/2005, with relative standard deviations (RSD) no larger than 10%.

Photodegradation of bensulphuron methyl in aqueous solution

Photodegradation of bensulphuron methyl, (methyl α-(4,6-dimethoxypyrimidin-2-carbamoylsulphamoyl)-o-toluate ester) was carried out in aqueous solution under UV light. The rate of photolysis followed first-order kinetics, with a half-life of 31.7u2009min at λu2009=u2009254u2009nm and 41.3u2009h at λu2009≥u2009290u2009nm, with significant correlation coefficients (0.9898 and 0.9625, respectively). The main photoproducts in distilled water were identified with a diode array detector and mass spectrometry. The results indicate that different reaction pathways are followed: cleavage of the sulphonylurea bridge, desulphonylation, which can proceed either by a carbon–sulphur cleavage or a nitrogen–sulphur cleavage and contraction of the sulphonylurea bridge. A mechanism which accounts for the formation of the photoproducts is proposed