H-beta zeolite-based dispersive solid-phase strategy for the multi-residue determination of pesticides

Abstract

In this work, electrostatic interactions, hydrogen bonding and other interactions between a variety of pesticides and H-beta zeolite are discussed based on thermodynamics (Gibbs free energy, enthalpy, and entropy). Combined with the physical properties of the target compounds (octanol-water partition coefficient and molar volume), the characteristics of the physical adsorption on the synthetic zeolite were analyzed, the results of H-beta zeolite adsorption showed that the adsorption rate had a nonlinear relationship with the physical properties, and the adsorption reaction was dominated by the adsorption on the surface and in the pores of the H-beta zeolite. Based on the principle of zeolite adsorption, the parameters of absorbent amount, adsorption time, sample pH, ion strength, sample volume and desorption solvent were optimized, a vortex-assisted dispersive solid-phase extraction procedure coupled with liquid chromatography-tandem mass spectrometry was developed for the analysis of multiple pesticides in surface water. The sample was adjusted by phosphate buffer or hydrochloric acid to pH 4, then adsorbed by 50 mg of zeolite within 10 min, adding 2% (g/v) sodium chloride to the solution. The absorbent was eluted with a mixture of acetonitrile-methanol containing 0.5% formic acid after separation, then filtered prior to analysis. The optimized vortex-assisted dispersive solid-phase extraction method simultaneously achieved a low adsorbent dosage, a high enrichment factor of 25, rapid pre-concentration for 30 min, a low solvent usage of 2 mL and multi-target simultaneous analysis. Method performance in terms of accuracy, precision, limit of detection, and limit of quantitation was performed to validate the reliability of the procedure. The proposed protocol achieved acceptable accuracy (recoveries between 62% and 107%), and precision (relative standard deviation < 20%). The limit of detection of the method was below 0.1 μg/L, and the limit of quantitation was 0.08 μg/L or 0.2 μg/L. The results indicated that zeolite is a promising adsorbent with high adsorption capacity. It has the advantages of being a fast, simple, green and economical method for determining residual pesticides in water.

Keywords: Adsorption; Dispersive solid-phase extraction; Pesticide; Thermodynamics; Zeolite.