Search

A palladium-catalyzed asymmetric tandem [3+2] cycloaddition/allylation of methylene-trimethylenemethane is presented, providing the functionalized chiral hexahydropyrazolo[5,1- a]isoquinoline derivatives in high yields with good to excellent enantioselectivities and moderate to good E: Z ratios. In the one-pot sequential tandem reactions/hydroxylation, ( E)-allylic alcohol products were obtained in good yields with excellent enantioselectivities.

This study reports the development of a novel multiplug filtration cleanup (m-PFC) procedure for analysis of pesticide residues in leek samples followed by gas chromatography-tandem mass spectrometry detection. The leek samples were initially purified following the dispersive solid-phase extraction with different sorbents to determine the most suitable proportioning of sorbent materials; then, the m-PFC method was carried out by applying the streamlined procedure with syringes. Average recoveries of most pesticides were in the range from 70.2 to 126.0% with the relative standard deviation < 20% with the m-PFC process. The limits of detection were 0.03-3.3 μg kg(-1). The limits of quantification were 0.1-10 μg kg(-1). The m-PFC process is convenient and time-efficient, taking just a few seconds per sample. Finally, the developed method was successfully applied to the determination of pesticide residues in market samples. In that analysis, 35 pesticides were detected in 29 samples, with values ranging from 2.0 to 9353.1 μg kg(-1).

This study reports the development and validation of a novel rapid cleanup method based on multiple-walled carbon nanotubes in a packed column filtration procedure for analysis of pesticide residues followed by gas chromatography-triple-quadruple tandem mass spectrometry detection. The cleanup method was carried out by applying the streamlined procedure on a multiplug filtration cleanup column with syringes. The sorbent used for removing the interferences in the matrices is multiple-walled carbon nanotubes mixed with anhydrous magnesium sulfate. The proposed cleanup method is convenient and time-saving as it does not require any solvent evaporation, vortex, or centrifugation procedures. It was validated on 186 pesticides and 3 tomato product matrices spiked at two concentration levels of 10 and 100 μg kg(-1). Satisfactory recoveries and relative standard deviations are shown for most pesticides using the multiplug filtration cleanup method in tomato product samples. The developed method was successfully applied to the determination of pesticide residues in market samples.