Determination of Residual Triflumezopyrim Insecticide in Agricultural Products through a Modified QuEChERS Method.

A rapid and simple analytical method for triflumezopyrim, a new class of mesoionic insecticides and commercialized molecules from DuPont, was developed with a modified QuEChERS method. The pH adjustment was used to improve the extraction efficiency of acetonitrile solvent, and dispersive solid-phase extraction was employed for the clean-up process. The five selected food commodities were used to verify the present optimized method, which displayed good linearity with an excellent correlation coefficient (R2 = 0.9992-0.9998) in the 0.003-0.30 mg/kg calibration range. The method limits of detection (LOD) and quantification (LOQ) were determined to be a value of 0.003 and 0.01 mg/kg, respectively. The mean recovery for the triflumezopyrim was in the 89.7-104.3% range. The relative standard deviations were ≤9.8% for intra- (n = 5) and inter-day (n = 15) precisions at concentrations of 0.01, 0.1, and 0.5 mg/kg in the five representative samples. The matrix effect has been calculated to confirm the effect during ionization of the analyte in the UPLC-MS/MS. The matrix effects of the instrumental analysis showed that triflumezopyrim was less susceptible to matrices. The proposed analytical method in this study has effectively improved the accuracy, selectivity, and sensitivity for the determination of triflumezopyrim in agricultural commodities; therefore, it can serve as a reference method for the establishment of maximum residue limits (MRLs).

Selective colorimetric sensing of anions in aqueous media through reversible covalent bonding.

Selective colorimetric sensing of anions in aqueous media has been studied, which involves reversible covalent bonding as key binding interactions. By introducing a simple nitro chromophore into an o-(carboxamido)trifluoroacetophenone ionophore that recognizes anions through reversible covalent bonding, we have realized a complete selectivity in colorimetric sensing of cyanide among competing anions such as fluoride, acetate, and dihydrogen phosphate in aqueous media. Such selectivity is explained by dominant reversible covalent bonding over hydrogen bonding, which leads to indirect internal charge transfer. The sensing system is readily converted into a polymeric analogue, demonstrating its potential applicability to develop a naked eye detection material for highly toxic cyanide ions.

Fluorescence modulation in anion sensing by introducing intramolecular H-bonding interactions in host-guest adducts.

Fluorescence signaling in anion binding is modulated from quenching to enhancement by intramolecular H-bonding stabilization of anion-ionophore adducts; the intramolecular H-bonding is suggested to suppress the quenching processes otherwise possible and increase the conformational rigidity of the anionic adducts, leading to fluorescence enhancement in a selective fashion towards cyanide ion, among the various anions examined.