A quick analytical method using direct solid sample introduction and GC-ECD for pesticide residues analysis in crops

In this work, an analytical method for GC using direct solid sample introduction was developed to tackle the problem regarding quick detection of pesticide residue in crops and large-scale screening of samples. 10 mg of the crop solid sample without sample pre-treatment was directly introduced into a modified split/splitless injector for GC analysis. A split/splitless injector was modified to quickly remove oxygen and low boiling-point matrices of the sample. The whole sampling procedure was simple and it required less than 5 min. The experimental parameters including injector-port temperature, removal of oxygen and low boiling point matrices, size and the amount of the solid sample, oven temperature program were studied. Satisfactory recoveries of 6 pesticides (methyl parathion, fenitrothion, aldrin, dieldrin, endosulfan, o,p′-DDT) were obtained in maize and rice sample. Relative standard deviation was less than 15%. Experimental results showed that the proposed method was quick and reliable for pesticide residues analysis in crops.     

Photochromic Dithienylethene‐Containing Boron(III) Ketoiminates: Modulation of Photo‐Responsive Behavior through Variation of Intramolecular Motion

A series of dithienylethene‐containing boron(III) ketoiminates, as well as their corresponding β‐ketoimine ligands, have been synthesized and characterized. The photophysical, electrochemical, and photochromic properties of the compounds have been studied. Photocyclization has been found to be suppressed upon introduction of a phenyl substituent on the nitrogen atom of the β‐ketoiminate core, whereas photochromism could be observed by replacement of the phenyl substituent with a bulky mesityl group. It is believed that the steric effect of the mesityl unit restricts molecular rotation, resulting in such a prominent difference in the photochromic properties.