MIL-101(Cr)/MWCNTs-functionalized melamine sponges for solid-phase extraction of triazines from corn samples, and their subsequent determination by HPLC-MS/MS.

In the presented work, we proposed the use of polyvinylidene difluoride (PVDF) as a coupling agent to load MIL-101(Cr) and carboxylated multi-walled carbon nanotubes (MWCNTs) on the skeleton of melamine sponge (MeS) for the preparation of novel extraction media with high-efficiency. The morphology and structure of this composite were characterized by scanning electron microscopy (SEM) analyses. The obtained MIL-101(Cr)/MWCNTs functionalized MeS(MIL/M-MeS) cube was used as a sorbent for the solid-phase extraction (SPE) of six triazines (Atraton, Simetryne, Prometon, Ametryn, Propazine, and Prometryn) spiked corn samples. Several parameters that may affect the extraction efficiencies, including type and volume of extraction solvent, times of ultrasonic extraction, adsorption, and desorption; type and volume of desorption solvent, were optimized. This was followed by elution containing the herbicides, which were quantified using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Under optimum conditions, the analytical method for the preparation of MIL/M-MeS cube produced satisfactory recoveries and repeatability. The LODs of the method when applied to spiked corn samples were in the range of 0.01-0.04 ng g (LODs = 3δ/k). The relative intra- and inter-day recoveries ranged from 90.30 to 116.50% and 92.38-116.24%, respectively, and relative standard deviations ranged from 1.08 to 12.32% and 5.36-16.23%, respectively.