Magnetic solid-phase extraction of pyrethroid and neonicotinoid insecticides separately in environmental water samples based on alkaline or acidic group-functionalized mesoporous silica.

Pyrethroids and neonicotinoids are widely used insecticides. However, their residues have unfavorable effects on ecological systems. Magnetic solid phase extraction is a reliable pretreatment method for a better detection of insecticides at low concentrations. In this work, amino- and carboxyl-functionalized magnetic KIT-6 were designed according to the electron-accepting groups of pyrethroid molecules and electron-donating groups with neonicotinoid structures. The characterization of these two materials was conducted using transmission electron microscopy, scanning electron microscopy, nitrogen adsorption-desorption analysis, etc. The aminated composite was applied to the magnetic solid phase extraction of pyrethroid insecticides while the carboxylic one was applied to neonicotinoids, and the adsorption effects were comprehensively compared for the first time. The material dosage, solution pH, and some factors that influenced the recovery were studied and optimized. The adsorption processes of the materials were all spontaneous and exothermic. They also fitted well with pseudo-second order kinetics and Langmuir adsorption isotherms. Both physical (pore function) and chemical (electrostatic interaction) adsorption mechanisms were present in the process. The two nanocomposites were then successfully used to enrich the two kinds of insecticides in environmental water samples. The proposed method has great application potential for insecticide monitoring in complex environmental samples.